Seaweed Extracts Enhance Salam Turfgrass Performance during Prolonged Irrigation Intervals and Saline Shock

The interaction effect of water deficit stress and seaweed extract on phytochemical characteristics and antioxidant activity of licorice (Glycyrrhiza glabra L.)

Introduction

With increasing drought stress due to climate change and water scarcity, the agricultural sector has sought innovative strategies to mitigate the detrimental effects on crop productivity. One approach that has received significant attention is the use of fertilizers and biostimulants as potential means of alleviating drought stress.

Methods

In this study, five different irrigation levels including 100% (control), 80% (slight stress), 60% (mild stress), 40% (moderate stress), and 20% (severe stress) of field capacity (FC) and seaweed extract (SWE) at three concentrations (0, 5, and 10 g/L) were applied to the pots containing one-year-old licorice (Glycyrrhiza glabra L.) plants in a factorial completely randomized design experiment with three replications for eight weeks.

Results and discussion

The glycyrrhizic acid content increased with water stress intensity without the application of SWE until severe (20% FC) water stress treatment. The application of 10 g/L SWE under 100% FC led to a significant increase in the glycyrrhizic acid value (32.5±0.889 mg/g DW) compared with non-SWE application (30.0±1.040 mg/g DW). The maximum glabridin content (0.270±0.010 mg/g DW) was obtained under irrigation of 20% field capacity with 10 g/L SWE application. In addition, the activity of the all studied enzymes such as APX (ascorbate peroxidase), CAT (catalase), POD (peroxidase), and SOD (superoxide dismutase) were boosted by increasing the water stress levels. The use of SWE further enhanced the increase of some of these metabolites and enzymes, which, in turn, helped the plant to tolerate stress conditions through the scavenging of more ROS (Reactive oxygen species), wherein for this purpose, the SWE 10 g/L was more effective than other concentration. The plants efficiently eliminated ROS driven from drought stress by both non-enzymatic and enzymatic systems.

Potential of Plant-Based Extracts to Alleviate Sorbitol-Induced Osmotic Stress in Cabbage Seedlings

In light of expected climate change, it is important to seek nature-based solutions that can contribute to the protection of our planet as well as to help overcome the emerging adverse changes. In an agricultural context, increasing plant resistance to abiotic stress seems to be crucial. Therefore, the scope of the presented research was focused on the application of botanical extracts that exerted positive effects on model plants growing under controlled laboratory conditions, as well as plants subjected to sorbitol-induced osmotic stress. Foliar spraying increased the length and fresh mass of the shoots (e.g., extracts from Taraxacum officinale, Trifolium pratense, and Pisum sativum) and the roots (e.g., Solidago gigantea, Hypericum perforatum, and Pisum sativum) of cabbage seedlings grown under stressful conditions, as well as their content of photosynthetic pigments (Pisum sativum, Lens culinaris, and Hypericum perforatum) along with total phenolic compounds (Hypericum perforatum, Taraxacum officinale, and Urtica dioica). The antioxidant activity of the shoots measured with the use of DDPH (Pisum sativum, Taraxacum officinale, Urtica dioica, and Hypericum perforatum), ABTS (Trifolium pratense, Symphytum officinale, Valeriana officinalis, Pisum sativum, and Lens culinaris), and FRAP (Symphytum officinale, Valeriana officinalis, Urtica dioica, Hypericum perforatum, and Taraxacum officinale) assays was also enhanced in plants exposed to osmotic stress. Based on these findings, the most promising formulation based on Symphytum officinale was selected and subjected to transcriptomic analysis. The modification of the expression of the following genes was noted: Bol029651 (glutathione S-transferase), Bol027348 (chlorophyll A-B binding protein), Bol015841 (S-adenosylmethionine-dependent methyltransferases), Bol009860 (chlorophyll A-B binding protein), Bol022819 (GDSL lipase/esterase), Bol036512 (heat shock protein 70 family), Bol005916 (DnaJ Chaperone), Bol028754 (pre-mRNA splicing Prp18-interacting factor), Bol009568 (heat shock protein Hsp90 family), Bol039362 (gibberellin regulated protein), Bol007693 (B-box-type zinc finger), Bol034610 (RmlC-like cupin domain superfamily), Bol019811 (myb_SHAQKYF: myb-like DNA-binding domain, SHAQKYF class), Bol028965 (DA1-like Protein). Gene Ontology functional analysis indicated that the application of the extract led to a decrease in the expression of many genes related to the response to stress and photosynthetic systems, which may confirm a reduction in the level of oxidative stress in plants treated with biostimulants. The conducted studies showed that the use of innovative plant-based products exerted positive effects on crops and can be used to supplement current cultivation practices.

Application of seaweed extracts to mitigate biotic and abiotic stresses in plants

Agriculture sector is facing a lot of constraints such as climate change, increasing population and the use of chemicals, and fertilizers which have significant influence on sustainability. The excessive usage of chemical fertilizers and pesticides has created a significant risk to humans, animals, plants, and the environment. To reduce the dependency on chemical fertilizers and pesticides a biological-based alternative is required. Seaweeds are essential marine resources that contain bioactive compounds and they have several uses in agriculture. The use of seaweed extracts in agriculture can mitigate stress, enhance nutrient efficiency, and boost plant growth. The use of seaweed extracts and their components activate several signaling pathways and defense-related genes/enzymes. In this review, an attempt has been made to explain how seaweed extracts and their bioactive components induce tolerance and promote growth under stress conditions.

Supplementation with Ascophyllum nodosum extracts mitigates arsenic toxicity by modulating reactive oxygen species metabolism and reducing oxidative stress in rice

Ascophyllum nodosum extract (ANE) is considered as an effective source of biostimulants that have the potential of ameliorating the negative impact of different abiotic stresses in plants. Considering the growth-promoting ability and other regulatory roles of ANE, the present investigation was executed to evaluate the role of ANE in conferring arsenic (As) tolerance in rice (Oryza sativa L. cv. BRRI dhan89). Rice seedlings (35-d-old) were exposed to two doses of sodium arsenate (As1 - 50 mg As kg-1 soil; As2 - 100 mg As kg-1 soil) at 25 days after transplanting through irrigation, whereas only water was applied to the control. Foliar application of 0.1% ANE was also supplemented under control as well as As-stressed conditions at 7 days intervals for 5 times. Arsenic-induced oxidative stress was evident through a sharp increase in lipid peroxidation, hydrogen peroxide, methylglyoxal, and electrolyte leakage in the As-treated plants. As a consequence, plant growth and biomass, leaf relative water content, as well as yield attributes were reduced noticeably. On the other hand, ANE supplemented plants accumulated enhanced levels of ascorbate and glutathione, their redox balance, and the activities of antioxidant and glyoxalase enzymes viz. ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, catalase, glutathione peroxidase, and activities of glyoxalase I and glyoxalase II, respectively. Furthermore, relative water content, plant growth, yield attributes and yield were increased in the As-treated rice plants with ANE supplementation. The results reflected that foliar spray with ANE alleviated As-induced oxidative stress in rice plants by modulating the antioxidative defense and glyoxalase system.

Turfgrass Salinity Stress and Tolerance-A Review

Turfgrasses are ground cover plants with intensive fibrous roots to encounter different edaphic stresses. The major edaphic stressors of turfgrasses often include soil salinity, drought, flooding, acidity, soil compaction by heavy traffic, unbalanced soil nutrients, heavy metals, and soil pollutants, as well as many other unfavorable soil conditions. The stressors are the results of either naturally occurring soil limitations or anthropogenic activities. Under any of these stressful conditions, turfgrass quality will be reduced along with the loss of economic values and ability to perform its recreational and functional purposes. Amongst edaphic stresses, soil salinity is one of the major stressors as it is highly connected with drought and heat stresses of turfgrasses. Four major salinity sources are naturally occurring in soils: recycled water as the irrigation, regular fertilization, and air-borne saline particle depositions. Although there are only a few dozen grass species from the Poaceae family used as turfgrasses, these turfgrasses vary from salinity-intolerant to halophytes interspecifically and intraspecifically. Enhancement of turfgrass salinity tolerance has been a very active research and practical area as well in the past several decades. This review attempts to target new developments of turfgrasses in those soil salinity stresses mentioned above and provides insight for more promising turfgrasses in the future with improved salinity tolerances to meet future turfgrass requirements.

Nanoparticles assisted regulation of oxidative stress and antioxidant enzyme system in plants under salt stress: A review

The global biomass production from agricultural farmlands is facing severe constraints from abiotic stresses like soil salinization. Salinity-mediated stress triggered the overproduction of reactive oxygen species (ROS) that may result in oxidative burst in cell organelles and cause cell death in plants. ROS production is regulated by the redox homeostasis that helps in the readjustment of the cellular redox and energy state in plants. All these cellular redox related functions may play a decisive role in adaptation and acclimation to salinity stress in plants. The use of nanotechnology like nanoparticles (NPs) in plant physiology has become the new area of interest as they have potential to trigger the various enzymatic and non-enzymatic antioxidant capabilities of plants under varying salinity levels. Moreover, NPs application under salinity is also being favored due to their unique characteristics compared to traditional phytohormones, amino acids, nutrients, and organic osmolytes. Therefore, this article emphasized the core response of plants to acclimate the challenges of salt stress through auxiliary functions of ROS, antioxidant defense system and redox homeostasis. Furthermore, the role of different types of NPs mediated changes in biochemical, proteomic, and genetic expressions of plants under salt stress have been discussed. This article also discussed the potential limitations of NPs adoption in crop production especially under environmental stresses.

The Biostimulant Effect of Hydroalcoholic Extracts of Sargassum spp. in Tomato Seedlings under Salt Stress

Currently, the use of biostimulants in agriculture is a tool for mitigating certain environmental stresses. Brown algae extracts have become one of the most important categories of biostimulants in agriculture, and are derived from the different uses and positive results obtained under optimal and stressful conditions. This study aimed to examine the efficacy of a foliar application of a hydroalcoholic extract of Sargassum spp. and two controls (a commercial product based on Ascophyllum nodosum and distilled water) with regard to growth, the antioxidant system, and the expression of defense genes in tomato seedlings grown in nonsaline (0 mM NaCl) and saline (100 mM NaCl) conditions. In general, the results show that the Sargassum extract increased the growth of the seedlings at the end of the experiment (7.80%) compared to the control; however, under saline conditions, it did not modify the growth. The Sargassum extract increased the diameter of the stem at the end of the experiment in unstressed conditions by 14.85% compared to its control and in stressful conditions by 16.04% compared to its control. Regarding the accumulation of total fresh biomass under unstressed conditions, the Sargassum extract increased it by 19.25% compared to its control, and the accumulation of total dry biomass increased it by 18.11% compared to its control. Under saline conditions, the total of fresh and dry biomass did not change. Enzymatic and nonenzymatic antioxidants increased with NaCl stress and the application of algal products (Sargassum and A. nodosum), which was positively related to the expression of the defense genes evaluated. Our results indicate that the use of the hydroalcoholic extract of Sargassum spp. modulated different physiological, metabolic, and molecular processes in tomato seedlings, with possible synergistic effects that increased tolerance to salinity.

Red-seaweed biostimulants differentially alleviate the impact of fungicidal stress in rice (Oryza sativa L.)

Red seaweed-derived biostimulants facilitate plant health and impart protection against abiotic stress conditions by their bioactive compounds and plant nutrients. The potency of red seaweed biostimulants (LBS6 and LBD1) on rice cv. IR-64 in response to fungicides induced stress was investigated in this study. Foliar application of LBS6 maintained the stomatal opening and leaf temperature under the fungicidal stress condition. Reactive Oxygen Species (ROS) such as hydrogen peroxide and superoxide radicals were significantly reduced in LBS6-treated stressed plants. After applying seaweed biostimulants, ROS production was stabilized by antioxidants viz., CAT, APX, SOD, POD, and GR. LBS-6 application increased the Ca⁺ and K⁺ levels in the stressed plants, which perhaps interacted with ROS and stomatal opening signalling systems, respectively. In the rice plants, fungicidal stress elevated the expression of stress-responsive transcriptional factors (E2F, HSFA2A, HSFB2B, HSFB4C, HSFC1A, and ZIP12). A decline in the transcript levels of stress-responsive genes was recorded in seaweed treated plants. For the first time, we present an integrative investigation of physicochemical and molecular components to describe the mechanism by which seaweed biostimulants in rice improve plant health under fungicidal stress conditions.

Influence of Ascophyllum nodosum Extract Foliar Spray on the Physiological and Biochemical Attributes of Okra under Drought Stress

Drought stress restricts the growth of okra (Abelmoschus esculentus L.) primarily by disrupting its physiological and biochemical functions. This study evaluated the role of Ascophyllum nodosum extract (ANE) in improving the drought tolerance of okra. Drought stress (3 days (control), 6 days (mild stress), and 9 days (severe stress)) and 4 doses of ANE (0, 0.1%, 0.2%, and 0.3%) were imposed after 30 days of cultivation. The results indicate that drought stress decreases the chlorophyll content (total chlorophyll, chlorophyll a, chlorophyll b, and carotenoid) but increases the activity of anthocyanin, proline, and antioxidant enzymes such as ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT). Physiological and biochemical plant disturbances and visible growth reduction in okra under drought stress were significantly decreased by the application of ANE foliar spray. ANE spray (0.3%) significantly increased the chlorophyll abundance and activity of anthocyanin, proline, and antioxidants (APX, POD, and CAT). ANE regulated and improved biochemical and physiological functions in okra under both drought and control conditions. The results of the current study show that ANE foliar spray may improve the growth performance of okra and result in the development of drought tolerance in okra.

Fucoidan and Alginate from the Brown Algae Colpomenia sinuosa and Their Combination with Vitamin C Trigger Apoptosis in Colon Cancer

Brown seaweeds are producers of bioactive molecules which are known to inhibit oncogenic growth. Here, we investigated the antioxidant, cytotoxic, and apoptotic effects of two polysaccharides from the brown algae Colpomenia sinuosa, namely fucoidan and alginate, in a panel of cancer cell lines and evaluated their effects when combined with vitamin C. Fucoidan and alginate were isolated from brown algae and characterized by HPLC, FTIR, and NMR spectroscopy. The results indicated that highly sulfated fucoidans had higher antioxidant and cytotoxic effects than alginate. Human colon cancer cells were the most sensitive to the algal treatments, with fucoidan having an IC50 value (618.9 µg/mL-1) lower than that of alginate (690 µg/mL-1). The production of reactive oxygen species was increased upon treatment of HCT-116 cells with fucoidan and alginate, which suggest that these compounds may trigger cell death via oxidative damage. The combination of fucoidan with vitamin C showed enhanced effects compared to treatment with fucoidan alone, as evidenced by the significant inhibitory effects on HCT-116 colon cancer cell viability. The combination of the algal polysaccharides with vitamin C caused enhanced degeneration in the nuclei of cells, as evidenced by DAPI staining and increased the subG1 population, suggesting the induction of cell death. Together, these results suggest that fucoidan and alginate from the brown algae C. sinuosa are promising anticancer compounds, particularly when used in combination with vitamin C.

Strategies and prospects for biostimulants to alleviate abiotic stress in plants

Global climate change-induced abiotic stresses (e.g., drought, salinity, extreme temperatures, heavy metals, and UV radiation) have destabilized the fragile agroecosystems and impaired plant performance and thereby reducing crop productivity and quality. Biostimulants, as a promising and eco-friendly approach, are widely used to address environmental concerns and fulfill the need for developing sustainable/modern agriculture. Current knowledge revealed that plant and animal derived stimulants (e.g., seaweeds and phytoextracts, humic substances, and protein hydrolysate) as well as microbial stimulants (e.g., plant beneficial bacteria or fungi) have great potential to elicit plant tolerance to various abiotic stresses and thus enhancing plant growth and performance-related parameters (such as root growth/diameter, flowering, nutrient use efficiency/translocation, soil water holding capacity, and microbial activity). However, to successfully implement biostimulant-based agriculture in the field under changing climate, the understanding of agricultural functions and action mechanism of biostimulants coping with various abiotic stresses at physicochemical, metabolic, and molecular levels is needed. Therefore, this review attempts to unravel the underlying mechanisms of action mediated by diverse biostimulants in relation to abiotic stress alleviation as well as to discuss the current challenges in their commercialization and implementation in agriculture under changing climate conditions.

Prospects for Abiotic Stress Tolerance in Crops Utilizing Phyto- and Bio-Stimulants

Environmental stressors such as salinity, drought, high temperature, high rainfall, etc. have already demonstrated the negative impacts on plant growth and development and thereby limiting productivity of the crops. Therefore, in the time to come, more sustainable efforts are required in agricultural practices to ensure food production and security under such adverse environmental conditions. A most promising and eco-friendly way to achieve this goal would be to apply biostimulants to address the environmental concerns. Non-microbial biostimulants such as humic substances (HA), protein hydrolysate, plant-based products and seaweed extracts (SWE), etc. and/or microbial inoculants comprising of plant growth-promoting microbes such as arbuscular mycorrhizal fungi (AMF), fluorescent and non-fluorescent Pseudomonas, Trichoderma spp., Bacillus spp. etc. have tremendous potentiality to enhance plant growth, flowering, crop productivity, nutrient use efficiency (NUE) and translocation, as well as enhancing tolerance to a wide range of abiotic stresses by modifying physiological, biological and biochemical processes of the crop-plants. Similarly, application techniques and timing are also important to achieve the desired results. In this article we discussed the prospects of using seaweed, microbial, and plant-based biostimulants either individually or in combination for managing environmental stresses to achieve food security in a sustainable way. Particular attention was given to the modifications that take place in plant's physiology under adverse environmental conditions and how different biostimulants re-program the host's physiology to withstand such stresses. Additionally, we also discussed how application of biostimulants can overcome the issue of nutrient deficiency in agricultural lands and improve their use efficiency by crop plants.

Biostimulants for the Regulation of Reactive Oxygen Species Metabolism in Plants under Abiotic Stress

Global food security for a growing population with finite resources is often challenged by multiple, simultaneously occurring on-farm abiotic stresses (i.e., drought, salinity, low and high temperature, waterlogging, metal toxicity, etc.) due to climatic uncertainties and variability. Breeding for multiple stress tolerance is a long-term solution, though developing multiple-stress-tolerant crop varieties is still a challenge. Generation of reactive oxygen species in plant cells is a common response under diverse multiple abiotic stresses which play dual role of signaling molecules or damaging agents depending on concentration. Thus, a delicate balance of reactive oxygen species generation under stress may improve crop health, which depends on the natural antioxidant defense system of the plants. Biostimulants represent a promising type of environment-friendly formulation based on natural products that are frequently used exogenously to enhance abiotic stress tolerance. In this review, we illustrate the potential of diverse biostimulants on the activity of the antioxidant defense system of major crop plants under stress conditions and their other roles in the management of abiotic stresses. Biostimulants have the potential to overcome oxidative stress, though their wider applicability is tightly regulated by dose, crop growth stage, variety and type of biostimulants. However, these limitations can be overcome with the understanding of biostimulants’ interaction with ROS signaling and the antioxidant defense system of the plants.

Effects of Conventional and Bokashi Hydroponics on Vegetative Growth, Yield and Quality Attributes of Bell Peppers

Due to consumers' awareness and concern about nutrition and health in different parts of the world, the adoption of organic hydroponics is increasing. This has led to a search for organic nutrient media. One of the viable nutrient sources for organic hydroponics is bokashi compost. The principal objective of this study was to compare the performance of 10% bokashi hydroponics with convention hydroponics for bell pepper production. The different hydroponics influenced vegetative growth parameters largely due to considerable differences in the mineral elements in both hydroponic systems. Stems of conventionally grown plants were significantly (p ≤ 0.05) thicker (10.2 mm) compared to those of the bokashi grown plants (7.3 mm). Conventionally grown plants had significantly (p ≤ 0.05) higher photosynthetic performance than bokashi grown plants; normalized difference vegetation index (NDVI) (78.80 versus 67.49), soil plant analysis development (SPAD; 73.89 versus 38.43), and quantum yield (QY; 0.64 versus 0.49). Leaf superoxide dismutase (SOD) activity in the leaves of bokashi grown plants (0.32 units/mg protein) was significantly (p ≤ 0.05) lower than in the leaves of conventionally grown plants (0.37 units/mg protein). This also corresponded to significantly (p ≤ 0.05) higher leaf sap content in the conventionally grown plant than bokashi grown plants. Furthermore, conventional hydroponics yielded three-fold greater pepper fruit per plant compared to bokashi. After 14 days of storage at 7 °C and 95% relative humidity, the firmness of both groups declined, especially for the bokashi grown fruit (27.73 shore unit), which was significantly lower compared to conventionally grown fruit (35.65 shore unit). However, there was an increase in carotenoid content in fruit grown in both hydroponic systems after storage. In conclusion, although bell pepper plant was successfully cultivated in bokashi hydroponics, the plant performance, fruit yield and postharvest quality were lower than conventional hydroponics. We believe that this study and its approach will provide future research with baseline information on optimizing media of bokashi hydroponics to produce bell pepper.

Ulva lactuca Extract and Fractions as Seed Priming Agents Mitigate Salinity Stress in Tomato Seedlings

The present study investigates the effect of Ulva lactuca extract as seed-priming agent for tomato plants under optimal and salinity stress conditions. The aims of this experiment were to assess the effect of seed priming using Ulva lactuca extract in alleviating the salinity stress tomato plants were subjected to, and to find out the possible mechanism of actions behind such a positive effect via means of fractionation of the crude extract and characterization. Salinity application decreased the plant biomass and altered different physiological traits of tomato. However, the application of Ulva lactuca methanol extract (ME) and its fractions (residual fraction (RF), chloroform fraction (CF), butanol fraction (BF), and hexane fraction (HF)) at 1 mg·mL^-1 as seed priming substances attenuated the negative effects of salinity on tomato seedlings. Under salinity stress conditions, RF application increased the tomato fresh weight; while ME, RF, and HF treatments significantly decreased the hydrogen peroxide (H₂O₂) concentration and antioxidant activity in tomato plants. The biochemical analyses of Ulva lactuca extract and fractions showed that the RF recorded the highest concentration of glycine betaine, while the ME was the part with the highest concentrations of total phenols and soluble sugars. This suggests that these compounds might play a key role in the mechanism by which seaweed extracts mitigate salinity stress on plants.

Biostimulant Properties of Seaweed Extracts in Plants: Implications towards Sustainable Crop Production

The use of seaweed-based bioproducts has been gaining momentum in crop production systems owing to their unique bioactive components and effects. They have phytostimulatory properties that result in increased plant growth and yield parameters in several important crop plants. They have phytoelicitor activity as their components evoke defense responses in plants that contribute to resistance to several pests, diseases, and abiotic stresses including drought, salinity, and cold. This is often linked to the upregulation of important defense-related genes and pathways in the plant system, priming the plant defenses against future attacks. They also evoke phytohormonal responses due to their specific components and interaction with plant growth regulation. Treatment by seaweed extracts and products also causes significant changes in the microbiome components of soil and plant in support of sustainable plant growth. Seaweed extracts contain a plethora of substances which are mostly organic, but trace levels of inorganic nutrient elements are also present. Fractionation of seaweed extracts into their components and their respective bioassays, however, has not yielded favorable growth effects. Only the whole seaweed extracts have been consistently proven to be very effective, which highlights the role of multiple components and their complex interactive effects on plant growth processes. Since seaweed extracts are highly organic, they are ideally suited for organic farming and environmentally sensitive crop production. They are also very compatible with other crop inputs, paving the way for an integrated management approach geared towards sustainability. The current review discusses the growth and functional effects evoked by seaweed extracts and their modes and mechanisms of action in crop plants which are responsible for elicitor and phytostimulatory activities. The review further analyses the potential value of seaweed extracts in integrated crop management systems towards sustainable crop production.

The Opportunity of Valorizing Agricultural Waste, Through Its Conversion into Biostimulants, Biofertilizers, and Biopolymers

The problems arising from the limited availability of natural resources and the impact of certain anthropogenic activities on the environment must be addressed as soon as possible. To meet this challenge, it is necessary, among other things, to reconsider and redesign agricultural systems to find more sustainable and environmentally friendly solutions, paying specific attention to waste from agriculture. Indeed, the transition to a more sustainable and circular economy should also involve the effective valorization of agricultural waste, which should be seen as an excellent opportunity to obtain valuable materials. For the reasons mentioned above, this review reports and discusses updated studies dealing with the valorization of agricultural waste, through its conversion into materials to be applied to crops and soil. In particular, this review highlights the opportunity to obtain plant biostimulants, biofertilizers, and biopolymers from agricultural waste. This approach can decrease the impact of waste on the environment, allow the replacement and reduction in the use of synthetic compounds in agriculture, and facilitate the transition to a sustainable circular economy.

Effects of Megafol on the Olive Cultivar 'Arbequina' Grown Under Severe Saline Stress in Terms of Physiological Traits, Oxidative Stress, Antioxidant Defenses, and Cytosolic Ca2

Salinity is one of the most impacting abiotic stresses regarding crop productivity and quality. Among the strategies that are attracting attention in the protection of crops from abiotic stresses, there is the use of plant biostimulants. In this study, Megafol (Meg), a commercial plant biostimulant, was tested on olive plants subjected to severe saline stress. Plants treated with salt alone showed substantial reductions in biomass production, leaf net photosynthesis (Pn), leaf transpiration rate (E), stomatal conductance (gs), and relative water content (RWC). In addition, samples stressed with NaCl showed a higher sodium (Na⁺) content in the leaves, while those stressed with NaCl and biostimulated with Meg increased the potassium (K⁺) content in the leaves, thus showing a higher K⁺/Na⁺ ratio. Salinity caused the accumulation of significant quantities of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) due to decreases in the activity of antioxidant enzymes, namely superoxide dismutase (SOD - EC 1.15.1.1), ascorbate peroxidase (APX - EC 1.11.1.11), guaiacol peroxidase (GPX - EC 1.11.1.9), and catalase (CAT - EC 1.11.1.6). When olive plants under saline stress were biostimulated with Meg, the plants recovered and showed physiological and biochemical traits much improved than salt stressed samples. Finally, Meg exhibited Ca²⁺-chelating activity in olive pollen grains, which allowed the biostimulant to exert this beneficial effect also by antagonizing the undesirable effects of hydrogen peroxide on Ca²⁺ metabolism.

Can biostimulants be used to mitigate the effect of anthropogenic climate change on agriculture? It is time to respond

Anthropogenic climate change, namely climate alterations induced by human activities, is causing some issues to agricultural systems for their vulnerability to extreme events. Forecasts predict a global population increase in the near years that will exacerbate this situation, elevating the global demand for food. It will pose severe concerns in terms of natural resource usage and availability. Agriculture is one of the anthropogenic activities that will be more affected in the future. Climate extremes menace to affect the quantity and quality of crop production severely. Drought, water and soil salinity are considered among the most problematic factors that anthropogenic climate change will increase. This complex and worrying scenario requires the urgent implementation of sustainable measures which are capable of improving crop yield and quality, fostering the robustness and resilience of cropping systems. Among the more current methodology, the use of natural plant biostimulants (PBs) has been proposed to improve plant resistance to abiotic environmental stresses. The advantage of using these substances is due to their effectiveness in improving crop productivity and quality. Therefore, in this review, the most recent researches dealing with the use of natural PBs for improving plant resistance to drought and salinity, in an anthropogenic climate change scenario, have been reported and critically discussed.

Increased soybean tolerance to water deficiency through biostimulant based on fulvic acids and Ascophyllum nodosum (L.) seaweed extract

To meet the growing demand for soybean it is necessary to increase crop yield, even in low water availability conditions. To circumvent the negative effects of water deficit, application of biostimulants with anti-stress effect has been adopted, including products based on fulvic acids and Ascophyllum nodosum (L.) seaweed extracts. In this study, we determined which formulation and dosage of a biostimulant is more efficient in promoting the recovery of soybean plants after stress due to water deficit. The experiment was conducted in a greenhouse, in a double-factorial randomized block design with two additional factors, four repetitions and eleven treatments consisting of three biostimulant formulations (F1, F2 and F3), and three dosages (0.25; 0.50 and 1.0 kg ha-1); a control with water deficit and a control without water deficit. Soybean plants were kept at 50% of the pot's water capacity for three days, then rehydrated and submitted to the application of treatments with biostimulant. After two days of recovery, growth, physiological, biochemical and yield parameters were evaluated. All plants that received the application of the biostimulant produced more than the water-stressed control plants. The biostimulant provided higher photosynthetic rates, more efficient mechanisms for dissipating excess energy and higher activities of antioxidant enzymes. Plants treated with biostimulant were more efficient in the recovery of the metabolic activities after rewatering, resulting in increased soybean tolerance to water deficit and reduced yield losses. The best result obtained was through the application of formulation 2 of the biostimulant at a dosage of 0.25 kg ha-1.

Enhancing Sustainability by Improving Plant Salt Tolerance through Macro- and Micro-Algal Biostimulants

Algal biomass, extracts, or derivatives have long been considered a valuable material to bring benefits to humans and cultivated plants. In the last decades, it became evident that algal formulations can induce multiple effects on crops (including an increase in biomass, yield, and quality), and that algal extracts contain a series of bioactive compounds and signaling molecules, in addition to mineral and organic nutrients. The need to reduce the non-renewable chemical input in agriculture has recently prompted an increase in the use of algal extracts as a plant biostimulant, also because of their ability to promote plant growth in suboptimal conditions such as saline environments is beneficial. In this article, we discuss some research areas that are critical for the implementation in agriculture of macro- and microalgae extracts as plant biostimulants. Specifically, we provide an overview of current knowledge and achievements about extraction methods, compositions, and action mechanisms of algal extracts, focusing on salt-stress tolerance. We also outline current limitations and possible research avenues. We conclude that the comparison and the integration of knowledge on the molecular and physiological response of plants to salt and to algal extracts should also guide the extraction procedures and application methods. The effects of algal biostimulants have been mainly investigated from an applied perspective, and the exploitation of different scientific disciplines is still much needed for the development of new sustainable strategies to increase crop tolerance to salt stress.

Polyphenols of Frangula alnus and Peganum harmala Leaves and Associated Biological Activities

Frangula alnus and Peganum harmala populations growing in Saudi Arabia might be rich sources of natural compounds with important biological activities. A high performance liquid chromatography diode array revealed several polyphenols in the leaf extracts for the first time, including p-coumaric acid, rosmarinic acid, chlorogenic acid, ferulic acid, quercitrin, rutoside, quercetin and trifolin in F. alnus; and hydrocaffeic acid, protocatechuic acid, rosmarinic acid, caffeic acid and cynaroside in P. harmala. F. alnus and P. harmala showed strong antioxidant effects attributed to the polyphenolic composition of leaves and reduction of reactive oxygen species (ROS) accumulation. F. alnus and P. harmala leaf extracts showed cytotoxic effects against Jurkat, MCF-7, HeLa, and HT-29 cancer cells using MTT and flow cytometry assays. These activities were attributed to the polyphenolic composition of leaves including quercitrin, trifolin and cymaroside, as well as the activation of caspase family enzymes 2, 6, 8 and 9 in treated cancer cells compared to control. The current findings of this study include a novel comprehensive investigation on the polyphenol composition and anticancer effects of leaf extracts of F. alnus and P. harmala from natural populations in Saudi Arabia.

Al-Mana F, Al-Yafrsi MA. Antioxidant and Biological Activities of Acacia saligna and Lawsonia inermis Natural Populations

Acacia saligna and Lawsonia inermis natural populations growing in Northern Saudi Arabia might be a valuable source of polyphenols with potent biological activities. Using high-performance liquid chromatography-diode array detection (HPLC-DAD), several polyphenols were detected tentatively in considerable amounts in the methanolic leaf extracts of A. saligna and L. inermis. A. saligna mainly contained rutoside, hyperoside, quercetin 3-glucuronide, gallic acid and p-coumaric acid, whereas those of L. inermis contained apigenin 5-glucoside, apigetrin and gallic acid. Strong antioxidant activities were found in the leaf extracts of both species due to the presence of hyperoside, quercetin 3-glucuronide, gallic acid, isoquercetin, p-coumaric acid, quercitrin and rutoside. A. saligna and L. inermis leaf extracts as well as hyperoside, apigenin 5-glucoside, and quercetin 3-glucuronide significantly reduced reactive oxygen species accumulation in all investigated cancer cells compared to the control. Methanolic leaf extracts and identified polyphenols showed antiproliferative and cytotoxic activities against cancer cells, which may be attributed to necrotic cell accumulation during apoptotic periods. Antibacterial activities were also found in both species leaf extracts and were twice as high in A. saligna than L. inermis due to the high composition of rutoside and other polyphenols. Finally, strong antifungal activities were detected, which were associated with specific phenols such as rutoside, hyperoside, apigenin 5-glucoside and p-coumaric acid. This is the first study exploring the polyphenolic composition of A. saligna and L. inermis natural populations in northern Saudi Arabia and aiming at the detection of their biological activities.

Eco-Physiological Traits and Phenylpropanoid Profiling on Potted Vitis vinifera L. cv Pinot Noir Subjected to Ascophyllum nodosum Treatments under Post-Veraison Low Water Availability

In Mediterranean regions, extreme weather conditions during the growing season may alter grapevine physiology and metabolism, thus modifying the quality of wines. The objective of this study was to investigate the effects of Ascophyllum nodosum treatments on plant physiology and berry metabolism in Vitis vinifera exposed to water stress. The experiment was performed on potted vines subjected to two irrigation regimes (well-watered, WW, and water stressed, WS) both associated with A. nodosum treatments (SWE), compared with control plants (CTRL). Gas exchanges, chlorophyll fluorescence, and water relations were monitored on SWE and CTRL leaves, both in WW and WS vines at three times. Moreover, the quantification of secondary metabolites and their partitioning were performed in berry skins. Plants treated with A. nodosum extract showed higher photosynthesis and stomatal conductance than CTRL in both irrigation regimes and maintained a better plant hydraulic conductivity at the end of the sampling period. In addition, secondary metabolites in berry skins and their partitioning were significantly affected by the treatments in both irrigation regimes. Our results suggest that foliar application of A. nodosum extract may help the acclimation of grapevines to post-veraison water stress, likely improving plant physiological and biochemical performances under environmental constraints.

Polyphenol Content and Biological Activities of Ruta graveolens L. and Artemisia abrotanum L. in Northern Saudi Arabia

Natural populations of Ruta graveolens L. and Artemisia abrotanum L. in northern Saudi Arabia may be a rich source of natural polyphenols with potential biological activities. Therefore, tentative high-performance liquid chromatography–diode array detection was used to analyze the polyphenol contents of leaf extracts. R. graveolens mainly contained the phenolic acids chlorogenic acid and p-coumaric acid and the flavonoids rutoside and quercetin, whereas those of A. abrotanum mainly contained the phenolic acids isochlorogenic acid and rosmarinic acid and the flavonoid quercetin. Leaf extracts of both species showed antioxidant activities due to the presence of quercetin, chlorogenic acid, and p-coumaric acid as well as antiproliferative and cytotoxic activities against cancer cells, which may be attributed to necrotic cell accumulation during the early and late apoptotic periods. Both species also exhibited antibacterial activity, although the activity was higher in R. graveolens due to the high contents of quercetin and other polyphenols. Finally, both species exhibited antifungal activities, which were associated with specific polyphenols. This is the first study to confirm the richness of polyphenols and wide spectrum of biological activities in natural populations of R. graveolens and A. abrotanum in northern Saudi Arabia.

Polyphenol Profile and Antimicrobial and Cytotoxic Activities of Natural Mentha × piperita and Mentha longifolia Populations in Northern Saudi Arabia

New sources of polyphenols with anticancer, antioxidant, and antimicrobial properties in arid environments are critical for the development of alternative medicines and natural remedies. This study explored the polyphenol profiles and biological activities of methanolic leaf extracts from natural Mentha × piperita and Mentha longifolia populations in northern Saudi Arabia. Chromatographic analyses identified several polyphenols in M. × piperita including phenolic acids: rosmarinic acid (1547.6 mg/100 g DW (dry weight)), cryptochlorogenic acid (91.7 mg/100 g DW), and chlorogenic acid (69.4 mg/100 g DW), as well as flavonoids: naringin (328.8 mg/100 g DW) and cynaroside (162.8 mg/100 g DW). The major polyphenols in M. longifolia were: rosmarinic acid (781.6 mg/100 g DW), cryptochlorogenic acid (191.1 mg/100 g DW), p-coumaric acid (113.0 mg/100 g DW), m-coumaric acid (112.2 mg/100 g DW), and chlorogenic acid (63.8 mg/100 g DW). M. × piperita and M. longifolia leaf extracts had high antioxidant activities due to the major polyphenols (cynaroside, rosmarinic and cryptochlorogenic acids). M. × piperita had higher activities against different cancer cells than M. longifolia. Naringin, cryptochlorogenic acid, and rosmarinic acid had the highest activities against cancer cells. The leaf extracts had antibacterial effects against most bacteria species (Pseudomonas aeruginosa was most sensitive), which was attributed to the polyphenols. Antifungal activities were similarly broad (Aspergillus flavus was most sensitive) and attributed to naringin, cryptochlorogenic acid, and caffeic acid. Populations of M. × piperita and M. longifolia in Northern Riyadh may be a valuable source of natural biologically active compounds.

Saudi Rosmarinus officinalis and Ocimum basilicum L. Polyphenols and Biological Activities

Investigating the polyphenolic profile of natural Rosmarinus officinalis and Ocimum basilicum populations may reveal essential compounds that have biological activities. Natural populations of R. officinalis and O. basilicum in Northern Riyadh were investigated by HPLC-DAD analyses. Several polyphenols, including rosmarinic acid, gentisic acid, 3,4-dihydroxyphenylacetic acid, rutoside, and others, out of 38 screened were confirmed. Rosmarinic acid was the major polyphenol in both of R. officinalis and O. basilicum. R. officinalis methanolic leaf extracts contained other phenols such as gentisic acid while O. basilicum contained also 3,4-dihydroxyphenylacetic acid and rutoside as well as others. R. officinalis showed higher antioxidant activities than O. basilicum using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and β-carotene bleaching assays. These higher activities are associated with a higher composition of rosmarinic acid in leaf extracts. The antioxidant activities of O. basilicum were attributed to identified phenols of rosmarinic acid, 3,4-dihydroxyphenylacetic acid, and rutoside. There were antiproliferative and cytotoxic activities of leaf extracts, as well as identified polyphenols, against several cancer cells. These activities were attributed to the accumulation of necrotic and apoptotic cells in treated cancer cells with leaf extracts as well as identified polyphenols. The antibacterial and antifungal activities of leaf extracts were mainly attributed to 3,4-dihydroxyphenylacetic acid and rutoside in O. basilicum and rosmarinic acid and caffeic acid in R. officinalis. This study proved that R. officinalis and O. basilicum natural populations might be considered as promising sources of natural polyphenols with biological activities.

Trends in Seaweed Extract Based Biostimulants: Manufacturing Process and Beneficial Effect on Soil-Plant Systems

The time when plant biostimulants were considered as "snake oil" is erstwhile and the skepticism regarding their agricultural benefits has significantly faded, as solid scientific evidences of their positive effects are continuously provided. Currently plant biostimulants are considered as a full-fledged class of agri-inputs and highly attractive business opportunity for major actors of the agroindustry. As the dominant category of the biostimulant segment, seaweed extracts were key in this growing renown. They are widely known as substances with the function of mitigating abiotic stress and enhancing plant productivity. Seaweed extracts are derived from the extraction of several macroalgae species, which depending on the extraction methodology lead to the production of complex mixtures of biologically active compounds. Consequently, plant responses are often inconsistent, and precisely deciphering the involved mechanism of action remains highly intricate. Recently, scientists all over the world have been interested to exploring hidden mechanism of action of these resources through the employment of multidisciplinary and high-throughput approaches, combining plant physiology, molecular biology, agronomy, and multi-omics techniques. The aim of this review is to provide fresh insights into the concept of seaweed extract (SE), through addressing the subject in newfangled standpoints based on current scientific knowledge, and taking into consideration both academic and industrial claims in concomitance with market's requirements. The crucial extraction process as well as the effect of such products on nutrient uptake and their role in abiotic and biotic stress tolerance are scrutinized with emphasizing the involved mechanisms at the metabolic and genetic level. Additionally, some often overlooked and indirect effects of seaweed extracts, such as their influence on plant microbiome are discussed. Finally, the plausible impact of the recently approved plant biostimulant regulation on seaweed extract industry is addressed.

Malus baccata var. gracilis and Malus toringoides Bark Polyphenol Studies and Antioxidant, Antimicrobial and Anticancer Activities

Exploring new sources of polyphenols with biological activities that work against human diseases is the target of natural product studies. This study determined the polyphenol composition of the bark of Malus species M. baccata var. gracilis (Rehder) T.C.Ku and M. toringoides (Rehder) Hughes, using high-performance liquid chromatography with a diode-array detector (HPLC-DAD) analysis. The antiproliferative, cytotoxic, antioxidant and antimicrobial applications of these extracts, as well as the identified phenol, were studied. The HPLC-DAD analysis confirmed three polyphenols in the extracts out of the 21 screened compounds: protocatechuic acid, gallic acid, and catechin. The major constituents in M. baccata and M. toringoides were protocatechuic acid, at 3.16 and 7.15 mg 100 g−1 dry weight (DW), respectively, and catechin, at 5.55 and 6.80 mg 100 g−1 DW, respectively. M. baccata and M. toringoides bark extracts showed antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene bleaching, and ferric-reducing antioxidant power (FRAP) assays, which were attributed to the dominance of protocatechuic acid. The highest antiproliferative and cytotoxic effects were against Jurkat cells. Against MCF-7 and Hela cells, there was necrotic cell accumulation in the early apoptotic as well as the late apoptotic phase. The bark extracts showed noticeable antibacterial effects against Listeria monocytogenes, Bacillus cereus, and Escherichia coli. Protocatechuic acid showed comparable results to bark extracts. There were antifungal effects against Aspergillus ochraceus, A. niger, and Candida albicans, and the activities were higher than the commercial reagent. M. baccata and M. toringoides could be considered as a new source of phenolic acids, including protocatechuic acid with anticancer, antibacterial antifungal, and antioxidant-promising effects.

Elevated Bioactivity of Ruta graveolens against Cancer Cells and Microbes Using Seaweeds

Human cancer and pathogenic microbes cause a significant number of deaths every year. Modulating current sources of natural products that control such diseases becomes essential. Natural algae, such as Ascophyllum nodosum and Ecklonia maxima, can modulate the metabolic processes as well the bioactivities of Ruta graveolens L. The R. graveolens plants were subjected to nine soil drenches of A. nodosum (7 mL L−1), E. maxima (7 mL L−1), or both extracts. Morphological performance, gas exchange parameters, and essential oils (EOs) composition (GC-MS) were studied and the bioactivity was assessed against several cancer cells and pathogenic bacteria or fungi. Treatment with A. nodosum + E. maxima seaweed extracts (SWE) led to the highest morphological performance and gas exchange parameters. The highest antiproliferative, apoptotic, and caspase-3/7 activities of EO were against HeLa in SWE mixture treated plants. The best EO antimicrobial activities were obtained against Staphylococcus aureus and Penicillium ochrochloron. SWE mixtures treated plants showed the best bioactivities against microbes and cancer cells. The highest abundance of 2-undecanone (62%) and 2-nonanone (18%) was found in plants treated with SWE mixtures and caused the best anticancer and antimicrobial effects. Seaweed mixtures act as natural elicitors of pharmaceutical industries and favored 2-undecanone and 2-nonanone in R. graveolens.

Tree Bark Phenols Regulate the Physiological and Biochemical Performance of Gladiolus Flowers

The postharvest physiology of cut flowers is largely dependent on vase life, which is the maximum number of days before flower senescence. The use of tree bark extracts (major forest plant residues), as an eco-friendly and natural antioxidant preservative in holding solutions, is a novel tool for extending flower longevity. The morphological, physiological, biochemical, and genetic responses of Gladiolus grandiflorus cut spikes to Magnolia acuminata and Taxus cuspidata bark extracts as additives in holding solutions were investigated. G. grandiflorus subjected to bark extracts as well as catechin and protocatechuic acid (main phenols) displayed significant increased longevity (up to 18 days), an increased number of open florets, and increased floret fresh weight. Increases in the relative water content, leaf chlorophyll, carotenoids, soluble sugars, and protein content were observed in addition to a reduction in microbial growth in the cut spikes. Gas exchange parameters were higher in the bark extract treatments than in the controls. Higher antioxidant activities were detected and associated with increased superoxide dismutase and catalase enzyme activities and reduced H2O2 accumulation. The bark extract treatments associated with reduced expression of GgCyP1 (produces cysteine protease) and increased expression of both GgDAD1 (defends against apoptotic activity) and GgEXPA1 (regulates petal expansion). Several mechanisms were implicated in these effects, including maintenance of water content, enhanced management of reactive oxygen species (ROS), increased sugar and protein composition, and control of microbial growth. Thus, bark extracts and isolated phenols could be developed as an eco-friendly, non-toxic, and cost-effective natural preservative for cut gladiolus flowers.

El-Ansary D. Mammillaria Species-Polyphenols Studies and Anti-Cancer, Anti-Oxidant, and Anti-Bacterial Activities

Discovering new natural resources of polyphenols is the aim of many recent studies in the field of natural product research. This study tentatively investigated the polyphenols profile of the stems of seven Mammillaria species (M. rhodantha, M. spinosissima, M. hahniana, M. crucigera, M. candida, M. albilanata, and M. muehlenpfordtii) using high performance liquid chromatography with DAD detector (HPLC-DAD) method. Furthermore, the anti-cancer, anti-oxidant, and anti-bacterial potentials of these extracts as well as major identified phenols were explored. The HPLC-DAD study confirmed the availability of six phenolic acids, including gentisic acid, chlorogenic acid, caffeic acid, protocatechuic acid, sinapic acid, and p-hydroxybenzoic acid. The dominant compounds were: gentisic acid in M. rhodantha and M. spinosissima; chlorogenic acid in M. muehlenpfordtii, M. crucigera, and M. rhodantha; and caffeic acid in M. rhodantha, M. crucigera, and M. spinosissima. Stems of Mammillaria sp. showed antiproliferative effects against HeLa, MCF-7, and Jurkat cells. In HeLa and MCF-7 cells, the best antiproliferative activities were found in the treatments with M. rhodantha, M. spinosissima, and M. muehlenpfordtii. The apoptotic assay of M. rhodantha, M. spinosissima, and M. muehlenpfordtii showed accumulation of necrotic cells in the early and late apoptotic phase. M. rhodantha, M. spinosissima, and M. muehlenpfordtii showed the highest anti-oxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene bleaching, and ferric reducing anti-oxidant power (FRAP) assays. M. rhodantha was the best source of antioxidants. Mammillaria sp. showed moderate anti-bacterial effects against bacteria and the highest effects were found using the extracts of M. rhodantha, M. spinosissima, M. crucigera and M. muehlenpfordtii against most bacteria. The anti-bacterial activities were attributed to other phenolic compounds (e.g., chlorogenic acid) than gentisic acid, which was not active against most bacteria. Mammillaria sp. could be considered to be an important natural source of phenolic acids with anti-cancer, anti-bacterial, and anti-oxidant activities.

Effects of Water Stress and Modern Biostimulants on Growth and Quality Characteristics of Mint

Natural biostimulants combine different elicitors that may influence economic properties of herbal crops, such as mint. Mint (Mentha longifolia L.) plants were subjected to three water levels based on container substrate capacity (CSC; 100% CSC, 70% CSC, and 50% CSC) and/or applications of four biostimulants (CRADLE™, Mobilizer™, Nanozim De’Lite™ [ND], and Nanozim NXT™ [NN]). ND and NN exhibited higher vegetative growth and root dry weight than the control (without biostimulants) and other treatments. NN produced the highest fresh and dry mint yields under all water levels. Irrigation water-use efficiency (IWUE) of NN was highest (2.78 kg m−3) with 70% CSC, whereas the control produced the lowest IWUE (1.85 kg m−3) with 100% CSC. Biostimulants boosted physiological and metabolic responses, including gas exchange, leaf water potential, relative water content, and proline accumulation of stressed plants. NN treatment with 70% CSC had the highest essential oil (EO) ratio (3.35%). Under 70% and 50% CSC with NN treatment, the proportion of 1,8-cineol increased and that of pulegone decreased in EOs. Increased antioxidant activities, reduced H2O2 levels, and increased catalase and superoxide dismutase activities were observed. Applications of ND and NN during water stress conditions increased economic and medicinal properties of mint EOs with applications in the agricultural and pharmaceutical industries.

Mattar M, Al-Yafrasi MA, El-Ansary DO, Zin El-Abedin TK, Yessoufou K. Polyphenol Profile and Pharmaceutical Potential of Quercus spp. Bark Extracts

Targeted profiling of polyphenols in trees may reveal valuable sources of natural compounds with major applications in pharmacology and disease control. The current study targeted the profiling of polyphenols using HPLC-DAD in Quercus robur, Q. macrocarpa and Q. acutissima bark extracts. Free radical scavenging of each extract was investigated using antioxidant assays. Antimicrobial activities against a wide spectrum of bacteria and fungi were explored, as well as anticancer activities against different cancer cell lines. The HPLC-DAD analyses revealed the availability of several polyphenols in high amounts, including ellagic acid (in Q. robur) and caffeic acid (in Q. macrocarpa) in all three species. The bioactivity assay revealed high antioxidant activity in Q. robur compared to that of the other species, as well as phenolic standards. The three oak bark extracts showed clear antibacterial activities against most bacteria tested, with the highest antibacterial activities in the extracts of Q. robur. In addition, the three extracts showed higher antibacterial activities against Pseudomonas aeruginosa, Micrococcus flavus, and Escherichia coli compared to that of other bacteria. There were strong antifungal activities against some fungi, such as Aspergillus flavus, Penicillium funiculosum, and Penicillium ochrochloron. There were also noticeable anticancer activities against MCF-7, HeLa, Jurkat, and HT-29 cell lines, with the highest anticancer activity in the extracts of Q. robur. This is the first study that reveals not only novel sources of important polyphenols (e.g., ellagic acid) in Q. robur, Q. macrocarpa and Q. acutissima bark but also their anticancer activities against diverse cancer cell lines.

Omeprazole alleviates water stress in peppermint and modulates the expression of menthol biosynthesis genes

Water stress is a worldwide agricultural challenge that limits crop growth and quality. Chemical compounds that promote tolerance to water stress, such as omeprazole showed recently promising results. The present study investigates the effect of weekly drenching applications of 0, 10, 50, 100, or 200 μM omeprazole on Mentha piperita (peppermint) subjected to water stress by watering at 100%, 70%, and 50% of container substrate capacity for 7 weeks in an experiment that spanned two seasons. Peppermint that received higher doses of omeprazole showed increased plant height, leaf number, leaf area, and dry weight under normal and water stress conditions. The amounts of chlorophyll and proline in the leaves as well as gas exchange increased in omeprazole-treated plants relative to the control plants. Omeprazole treatment also resulted in increased activity of the enzymes catalase and ascorbate peroxidase, reduced accumulation of the reactive oxygen species hydrogen peroxide, increase in the essential oil ratio, and improvement in essential oil composition. Omeprazole-treated plants showed higher ratios of menthol and menthone composition relative to the control plants. The changes in essential oil composition were associated with increased expression of genes associated with the menthol biosynthesis pathway. These findings indicate that omeprazole can ameliorate water stress in peppermint by increasing vegetative and root growth; increasing chlorophyll amount, photosynthetic rate, and gas exchange; reducing water loss by boosting leaf water potential and relative water content; increasing proline content; and modulating the gene expression of secondary metabolites.

Ascophyllum nodosum-Based Biostimulants: Sustainable Applications in Agriculture for the Stimulation of Plant Growth, Stress Tolerance, and Disease Management

Abiotic and biotic stresses limit the growth and productivity of plants. In the current global scenario, in order to meet the requirements of the ever-increasing world population, chemical pesticides and synthetic fertilizers are used to boost agricultural production. These harmful chemicals pose a serious threat to the health of humans, animals, plants, and the entire biosphere. To minimize the agricultural chemical footprint, extracts of Ascophyllum nodosum (ANE) have been explored for their ability to improve plant growth and agricultural productivity. The scientific literature reviewed in this article attempts to explain how certain bioactive compounds present in extracts aid to improve plant tolerances to abiotic and/or biotic stresses, plant growth promotion, and their effects on root/microbe interactions. These reports have highlighted the use of various seaweed extracts in improving nutrient use efficiency in treated plants. These studies include investigations of physiological, biochemical, and molecular mechanisms as evidenced using model plants. However, the various modes of action of A. nodosum extracts have not been previously reviewed. The information presented in this review depicts the multiple, beneficial effects of A. nodosum-based biostimulant extracts on plant growth and their defense responses and suggests new opportunities for further applications for marked benefits in production and quality in the agriculture and horticultural sectors.

Overexpression of AtWRKY30 Transcription Factor Enhances Heat and Drought Stress Tolerance in Wheat (Triticum aestivum L.)

Drought and heat factors have negative impacts on wheat yield and growth worldwide. Improving wheat tolerance to heat and drought stress is of the utmost importance to maintain crop yield. WRKY transcription factors help improve plant resistance to environmental factors. In this investigation, Arabidopsis WRKY30 (AtWRKY30) transcription factor was cloned and expressed in wheat. Plants growth, biomass, gas-exchange attributes, chlorophyll content, relative water content, prolines content, soluble proteins content, soluble sugars content, and antioxidant enzymes activities (catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX)) of the AtWRKY30-overexpressing wheat plants were higher than those of the wild type. However, levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide of the AtWRKY30-overexpressing wheat plants were significantly less than those of the wild-type. Additionally, the expression level of antioxidant enzyme-encoding genes and stress-responsive genes (ERF5a, DREB1, DREB3, WRKY19, TIP2, and AQP7) were significantly induced in the transgenic wheat plants in comparison with the wild type. In conclusion, the results demonstrated that AtWRKY30 overexpression promotes heat and drought tolerance in wheat by inducing gas-exchange attributes, antioxidant machinery, osmolytes biosynthesis, and stress-related gene expression. AtWRKY30 could serve as a potential candidate gene for improving stress tolerance in wheat.

Heuchera Creme Brulee and Mahogany Medicinal Value under Water Stress and Oligosaccharide (COS) Treatment

Food borne pathogens cause serious human illnesses and diseases and their control using natural bioactive compounds becomes essential for the progress of agricultural and food industries. Developing novel tools to enhance the medicinal values of traditional horticultural medicinal crops is one of the promising methods for achieving food borne pathogens control. In this study, oligosaccharide water solutions were applied to Heuchera Creme Brulee and Mahogany subjected to a normal irrigation interval (2 days) or to prolonged irrigation intervals (6 days) for 6 weeks. Plant morphological, physiological, and metabolic markers associated with the bioactivity of leaf extracts against selected microbes. Oligosaccharide-treated plants showed significant increases in all morphological parameters during normal and prolonged irrigation intervals as compared to those of the controls. Morphological improvement associated with a significant increase in chlorophyll, carbohydrates, proline, K, Ca, phenols, and free and total ascorbate and antioxidants. Superoxide dismutase, catalase, and ascorbate peroxidase activities were higher, while H₂O₂ accumulated to a lower extent in oligosaccharide-treated plants. These morphological and metabolic changes associated with increased antibacterial and antifungal activities of leaf extracts and their activities were comparable to antibiotics and antifungal agents (minimum inhibitory concentrations values were 0.5 -0.20 mg⁻¹mL for bacteria and 0.08 -0.20 mg⁻¹mL for fungi in Mahogany). The application of oligosaccharide and/or water stress might be of great value for producing natural bioactive compounds for food borne pathogens control.

Overexpression of StDREB2 Transcription Factor Enhances Drought Stress Tolerance in Cotton (Gossypium barbadense L.)

Drought stress significantly restricts plant growth and crop productivity. Cotton is the most important textile fiber and oilseed crop worldwide, and its cultivation is affected by drought stress, particularly in dry regions. Improving cotton tolerance to drought stress using the advanced genetic engineering technologies is a promising strategy to maintain crop production and fiber quality and meet the increasing worldwide fiber and oil demand. Dehydration-responsive element binding (DREB) transcription factors play a main role in regulating stresses-tolerance pathways in plant. This study investigated whether potato DREB2 (StDREB2) overexpression can improve drought tolerance in cotton. StDREB2 transcription factor was isolated and overexpressed in cotton. Plant biomass, boll number, relative water content, soluble sugars content, soluble protein content, chlorophyll content, proline content, gas-exchange parameters, and antioxidants enzymes (POD, CAT, SOD, GST) activity of the StDREB2-overexpressing cotton plants were higher than those of wild type plants. By contrast, the contents of malondialdehyde, hydrogen peroxide and superoxide anion of StDREB2-overexpressing transgenic plants were significantly lower than that of the wild type plants. Moreover, the transgenic cotton lines revealed higher expression levels of antioxidant genes (SOD, CAT, POD, GST) and stress-tolerant genes (GhERF2, GhNAC3, GhRD22, GhDREB1A, GhDREB1B, GhDREB1C) compared to wild-type plants. Taken together, these findings showed that StDREB2 overexpression augments drought stress tolerance in cotton by inducing plant biomass, gas-exchange characteristics, reactive oxygen species (ROS) scavenging, antioxidant enzymes activities, osmolytes accumulation, and expression of stress-related genes. As a result, StDREB2 could be an important candidate gene for drought-tolerant cotton breeding.

Bacillus firmus (SW5) augments salt tolerance in soybean (Glycine max L.) by modulating root system architecture, antioxidant defense systems and stress-responsive genes expression

Soil salinity is an adverse abiotic factor which reduces plant growth, yield and quality. Plant growth-promoting rhizobacteria (PGPR) have a great potential to enhance growth and alleviate saline stress effects without harming the environment via regulating physiological and molecular processes in plants. This study aimed at investigating Bacillus firmus SW5 effects on the performance of soybean (Glycine max L.) subjected to salt stress (0, 40 and 80 mM NaCl). Salinity stress mitigated the growth and biomass yield, root architecture traits, nutrient acquisition, chlorophyll level, transpiration rate (E), photosynthesis rate (Pn), stomatal conductance (gs), soluble proteins content, soluble sugars content and total phenolics and flavonoid contents of soybean plants. High salinity augmented the levels of osmolytes (glycine betaine and proline), hydrogen peroxide (H2O2), malondialdehyde (MDA) and the activities of antioxidant enzymes (APX, CAT, SOD and POD) in soybean plants. High salinity also induced the expression of antioxidant enzyme-encoding genes (APX, CAT, POD, Fe-SOD) and genes conferring tolerance to salinity (GmVSP, GmPHD2, GmbZIP62, GmWRKY54, GmOLPb, CHS) in soybean plants. On the other hand, inoculation of NaCl-stressed soybean plants with Bacillus firmus SW5 promoted the growth and biomass yield, chlorophyll synthesis, nutrient uptake, gas exchange parameters, osmolytes levels, total phenolic and flavonoid contents, and antioxidant enzymes activities, in comparison with the plants treated with NaCl alone. Bacillus firmus SW5 inoculation also significantly reduced the IC50 values for both DPPH and β-carotene-linoleic acid assays and indicated higher antioxidant activities in salt-stressed plants. Furthermore, contents of H2O2 and MDA were alleviated in salinity-stressed soybean plants inoculated with Bacillus firmus SW5, in comparison with those in plants exposed to NaCl alone. The antioxidant enzyme-encoding genes and stress-related genes exhibited the highest expression levels in soybean plants inoculated with Bacillus firmus SW5 and treated with 80 mM NaCl. Taken together, our results demonstrate the crucial role of Bacillus firmus SW5 in ameliorating the adverse effects of high salinity on soybean growth and performance via altering the root system architecture and inducing the antioxidant defense systems and stress-responsive genes expression.

Serratia liquefaciens KM4 Improves Salt Stress Tolerance in Maize by Regulating Redox Potential, Ion Homeostasis, Leaf Gas Exchange and Stress-Related Gene Expression

High salinity mitigates crop productivity and quality. Plant growth-promoting soil rhizobacteria (PGPR) improve plant growth and abiotic stress tolerance via mediating various physiological and molecular mechanisms. This study investigated the effects of the PGPR strain Serratia liquefaciens KM4 on the growth and physiological and molecular responsiveness of maize (Zea mays L.) plants under salinity stress (0, 80, and 160 mM NaCl). High salinity significantly reduced plant growth and biomass production, nutrient uptake, leaf relative water content, pigment content, leaf gas exchange attributes, and total flavonoid and phenolic contents in maize. However, osmolyte content (e.g., soluble proteins, proline, and free amino acids), oxidative stress markers, and enzymatic and non-enzymatic antioxidants levels were increased in maize under high salinity. On the other hand, Serratia liquefaciens KM4 inoculation significantly reduced oxidative stress markers, but increased the maize growth and biomass production along with better leaf gas exchange, osmoregulation, antioxidant defense systems, and nutrient uptake under salt stress. Moreover, it was found that all these improvements were accompanied with the upregulation of stress-related genes (APX, CAT, SOD, RBCS, RBCL, H⁺-PPase, HKT1, and NHX1), and downregulation of the key gene in ABA biosynthesis (NCED). Taken together, the results demonstrate the beneficial role of Serratia liquefaciens KM4 in improving plant growth and salt stress tolerance in maize by regulating ion homeostasis, redox potential, leaf gas exchange, and stress-related genes expression.

Fertigation: Nutrition, Stimulation and Bioprotection of the Root in High Performance

Temperature changes, drought, frost, and the presence of pest and diseases place enormous stress on crops, which implies that the potential performance of these crops may be affected. One of the main goals for agronomists, horticulturists, growers, physiologists, soil scientists, geneticists, plant breeders, phytopathologists, and microbiologists is to increase the food production on the same cultivable area and to ensure that they are safe and of high quality. Understanding the biophysical changes in soil will help to manage the crop's ability to cope with biotic and abiotic stress. Optimization is needed in the nutrition of crops, which involves the use of biostimulants to counter oxidative stress and the management of strain bioformulations (bacteria and fungi) that protect and stimulate roots for the acquisition of nutrients. The implementation of these strategies in fertigation programs improves crop yields. This article addresses the importance of the stimulation and the bioprotection of the root as a fundamental pillar in ensuring the high performance of a crop.

Genetic Variation and Alleviation of Salinity Stress in Barley (Hordeum vulgare L.)

Barley (Hordeum vulgare L.) represents one of the most important cereals cultivated worldwide. Investigating genetic variability and structure of barley is important for enhancing the crop productivity. This study aimed to investigate the diversity and structure of 40 barley genotypes originated from three European countries (France, the Netherlands, Poland) using amplified fragment length polymorphisms (AFLPs). It also aimed to study 5-aminolevulinic acid (ALA) effect on salinity tolerance of six barley genotypes. The expected heterozygosity (H_e) diverged from 0.126 to 0.501, with a mean of 0.348. Polymorphic information content (PIC) diverged from 0.103 to 0.482 across barley genotypes, with a mean of 0.316, indicating that barley genotypes are rich in a considerable level of genetic diversity. The 40 barley genotypes were further studied based on their geographical origin (Western Europe and Eastern Europe). The Eastern European region (Poland) has a higher barley variability than the Western European region (France and the Netherlands). Nei’s distance-based cluster tree divided the 40 barley accessions into two major clusters; one cluster comprised all the varieties originated from the Eastern European region, while the other major cluster included all accessions originated from the Western European region. Structure analysis results were in a complete concordance with our cluster analysis results. Slaski 2, Damseaux and Urbanowicki genotypes have the highest diversity level, whereas Carmen, Bigo and Cambrinus genotypes have the lowest level. The response of these six varieties to NaCl stress was also investigated. Salt stress (100 mM NaCl) slightly decreased levels of chlorophyll, carotenoid and osmolytes (proteins, soluble sugars, phenolics and flavonoids) in the leaves of Slaski 2, Damseaux and Urbanowicki genotypes at non-significant level, as compared to control samples. However, pigment contents and osmolytes in leaves of Carmen, Bigo and Cambrinus genotypes were significantly decreased by salt stress. Antioxidant enzyme activities were significantly increased in Slaski 2 genotype, but non-significantly increased in Carmen by salt stress. Priming Slaski 2 and Carmen cultivars with ALA under salt stress significantly induced pigment contents, antioxidants enzymes activity and stress-responsive genes expression, relative to NaCl-stressed plants. In conclusion, this study suggested a correlation between variability percentage and degree of salinity resistance. ALA improved salt tolerance in barley.

Analysis of Genetic Variation and Enhancement of Salt Tolerance in French Pea (Pisum Sativum L.)

Pisum sativum L. (field pea) is a crop of a high nutritional value and seed oil content. The characterization of pea germplasm is important to improve yield and quality. This study aimed at using fatty acid profiling and amplified fragment length polymorphism (AFLP) markers to evaluate the variation and relationships of 25 accessions of French pea. It also aimed to conduct a marker-trait associations analysis using the crude oil content as the target trait for this analysis, and to investigate whether 5-aminolevulinic acid (ALA) could enhance salt tolerance in the pea germplasm. The percentage of crude oil of the 25 pea genotypes varied from 2.6 to 3.5%, with a mean of 3.04%. Major fatty acids in all of the accessions were linoleic acid. Moreover, the 12 AFLP markers used were polymorphic. The cluster analysis based on fatty acids data or AFLP data divided the 25 pea germplasm into two main clusters. The gene diversity of the AFLP markers varied from 0.21 to 0.58, with a mean of 0.41. Polymorphic information content (PIC) of pea germplasm varied from 0.184 to 0.416 with a mean of 0.321, and their expected heterozygosity (He) varied from 0.212 to 0.477 with a mean of 0.362. The AFLP results revealed that the Nain Ordinaire cultivar has the highest level of genetic variability, whereas Elatius 3 has the lowest level. Three AFLP markers (E-AAC/M-CAA, E-AAC/M-CAC, and E-ACA/M-CAG) were significantly associated with the crude oil content trait. The response of the Nain Ordinaire and Elatius 3 cultivars to high salinity stress was studied. High salinity (150 mM NaCl) slightly reduced the photosynthetic pigments contents in Nain Ordinaire leaves at a non-significant level, however, the pigments contents in the Elatius 3 leaves were significantly reduced by high salinity. Antioxidant enzymes (APX-ascorbate peroxidase; CAT-catalase; and POD-peroxidase) activities were significantly induced in the Nain Ordinaire cultivar, but non-significantly induced in Elatius 3 by high salinity. Priming the salt-stressed Nain Ordinaire and Elatius 3 plants with ALA significantly enhanced the pigments biosynthesis, antioxidant enzymes activities, and stress-related genes expression, as compared to the plants stressed with salt alone. In conclusion, this study is amongst the first investigations that conducted marker-trait associations in pea, and revealed a sort of correlation between the diversity level and salt tolerance.

Synergetic effects of 5-aminolevulinic acid and Ascophyllum nodosum seaweed extracts on Asparagus phenolics and stress related genes under saline irrigation

Salinity is one of the major agricultural problems that may threat food security and limit the agricultural lands expansion worldwide. Exploring novel tools controlling saline conditions and increase valuable secondary metabolites in the horticultural crops might have outstanding results that serve humanity in the current century. The current study explores the effects of weekly seaweed extracts (7 mL L-1) and/or 5-aminolevulinic acid (3, 5 and 10 ppm) sprays on Asparagus aethiopicus plants subjected to saline stress conditions (2000 and 4000 ppm) for 6 weeks in two consecutive seasons of 2016 and 2017. Under saline conditions, there were stimulatory synergetic effects of seaweed extracts (SWE) and 5-aminolevulinic acid (ALA) on branch length and number of treated plants. Similar increases were also found in fresh and the dry weight of treated plants compared to control. These morphological improvements associated with increased accumulation of specific phenols (robinin, rutin, apigein, chlorogenic acid and caffeic acid) as revealed by High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). There were increases in the antioxidant activities of leaf extracts, chlorophyll content and sugars and proline accumulation. The transpiration and photosynthetic rates as well as the stomatal conductance were enhanced. The morphological and physiological improvements associated with increased expression of several genes responsible for water management (ANN1, ANN2 and PIP1), secondary metabolite production (P5CS1 and CHS) and antioxidants accumulation (APX1 and GPX3) in plants. Our findings indicate that SWE + ALA had stimulatory synergetic effects on the growth and secondary metabolites of A. aethiopicus subjected to saline conditions. Several mechanisms are involved in such effects including gas exchange control, sugar buildup, increasing non-enzymatic and enzymatic antioxidants control of reactive oxygen species accumulation as well as transcriptional and metabolic regulation of environmental stress.

Ascophyllum nodosum extract biostimulants and their role in enhancing tolerance to drought stress in tomato plants

Global changes in climate are leading to increased occurrence and duration of drought episodes with concurrent reduction in crop yields. Expansion of the irrigated land area does not appear to be a viable solution in many regions to deliver crop productivity. The development of crop drought tolerance traits by either genetic modification or plant breeding represent the principal approaches to meeting this challenge to date. Biostimulants are an emerging category of crop management products which can enhance crop productivity under abiotic stress conditions. The ability of some biostimulant products such as Ascophyllum nodosum extracts (ANE) to enhance the tolerance of crops to drought stress has been observed by growers. The objective of this study was to investigate if different commercial ANE biostimulants provided the same tolerance to tomato plants (cv. Moneymaker) subjected to a defined drought period. A compositional characterisation of the key macromolecules of ANEs was performed. In addition, the role of ANE biostimulants in inducing changes of chlorophyll and osmolytes levels, MDA production, dehydrin isoform pattern and dehydrin gene expression levels was assessed. The three ANE biostimulants evaluated were found to provide different levels of tolerance to drought stressed tomato plants. The level of drought tolerance provided was related to changes in the concentration of osmolytes and expression of tas14 dehydrin gene. Taken together, our results highlight that despite the fact all ANE biostimulants were manufactured from the same raw material, their ability to maintain crop productivity during and after drought stress was not the same.

Salicylic Acid-Regulated Antioxidant Mechanisms and Gene Expression Enhance Rosemary Performance under Saline Conditions

Salinity stress as a major agricultural limiting factor may influence the chemical composition and bioactivity of Rosmarinus officinallis L. essential oils and leaf extracts. The application of salicylic acid (SA) hormone may alleviate salinity stress by modifying the chemical composition, gene expression and bioactivity of plant secondary metabolites. In this study, SA was applied to enhance salinity tolerance in R. officinallis. R. officinallis plants were subjected to saline water every 2 days (640, 2,000, and 4,000 ppm NaCl) and 4 biweekly sprays of SA at 0, 100, 200, and 300 ppm for 8 weeks. Simulated salinity reduced all vegetative growth parameters such as plant height, plant branches and fresh and dry weights. However, SA treatments significantly enhanced these plant growth and morphological traits under salinity stress. Salinity affected specific major essential oils components causing reductions in α-pinene, β-pinene, and cineole along with sharp increases in linalool, camphor, borneol, and verbenone. SA applications at 100–300 ppm largely reversed the effects of salinity. Interestingly, SA treatments mitigated salinity stress effects by increasing the total phenolic, chlorophyll, carbohydrates, and proline contents of leaves along with decline in sodium and chloride. Importantly, this study also proved that SA may stimulate the antioxidant enzymatic mechanism pathway including catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) as well as increasing the non-enzymatic antioxidants such as free and total ascorbate in plants subjected to salinity. Quantitative real-time PCR analysis revealed that APX and 3 SOD genes showed higher levels in SA-treated rosemary under salinity stress, when compared to non-sprayed plants. Moreover, the expression level of selected genes conferring tolerance to salinity (bZIP62, DREB2, ERF3, and OLPb) were enhanced in SA-treated rosemary under salt stress, indicating that SA treatment resulted in the modulation of such genes expression which in turn enhanced rosemary tolerance to salinity stress.