The induction of salt stress tolerance by jasmonic acid treatment in roselle (Hibiscus sabdariffa L.) seedlings through enhancing antioxidant enzymes activity and metabolic changes

Integrated Action of Rhizobacteria with Aloe vera and Moringa Leaf Extracts Improves Defense Mechanisms in Hibiscus sabdariffa L. Cultivated in Saline Soil

Osmotic stress is a serious physiological disorder that affects water movement within the cell membranes. Osmotic stress adversely affects agricultural production and sustainability and is largely caused by soil salinity and water stress. An integrated nitrogen-fixing bacteria (NFB) soil amendment and an exogenous foliar application of Aloe vera leaf extract (ALE), and moringa leaf extract (MLE) were evaluated on roselle (Hibiscus sabdariffa L.) growth, calyx yield, secondary metabolites, and tolerance to osmotic stress in salt-affected soil. The osmotic stress markedly decreased above- and below-ground development of the roselle plant, but integrated NFB soil amendment with ALE or MLE foliar application significantly alleviated its negative impacts. Broadly, an improvement was observed in chlorophyll, carbohydrates, and protein levels following NFB and extracts foliar application, as well as a significant enhancement in antioxidant production (total phenols, ascorbic acid, and FRAP), which decreased peroxide production and increased stress tolerance in plants. Under osmotic stress, the roselle calyx revealed the highest anthocyanin levels, which declined following NFB soil amendment and foliar extract application. Additionally, an enhancement in nitrogen (N), phosphorus (P), and potassium (K) contents and the K/Na ratio, along with a depression in sodium (Na) content, was noticed. The integrated application of Azospirillum lipoferum × ALE exhibited the best results in terms of enhancing above- and below-ground growth, calyx yield, secondary metabolites, and tolerance to osmotic stress of the roselle plants cultivated in the salt-affected soil.

Effect of exogenous taurine on pea (Pisum sativum L.) plants under salinity and iron deficiency stress

Soil salinity and Fe deficiency affect plant growth and survival by changing nutrient availability and disrupting water balance. Natural and human activities, such as evaporation and deforestation, can intensify these soil conditions. Taurine, a novel growth regulator, holds promise in mediating plant defense responses. Its effects on defense responses are still unclear. Previously, taurine showed potential in improving clover tolerance to alkaline stress and manganese toxicity. Taurine impact on plant growth under Fe deficiency and salinity stress remains uninvestigated. A pot experiment was conducted to evaluate the effects of taurine on pea plant growth, ion uptake, and defense strategies in response to salt stress and Fe deficiency. Iron deficiency was established by substituting 0.1 mM FeSO4 for 0.1 mM Fe-EDTA in the nutrient solution. Salinity stress was induced by incorporating a mixture of NaCl, MgCl2, KCl, Na2SO4, Na2CO3, NaHCO3 and CaCl2 in a 1:1:1:1:1:1:1 ratio to produce a salinity concentration of 100 mM. The simultaneous imposition of salinity and Fe deficiency significantly exacerbated oxidative stress, as evidenced by elevated levels of relative membrane permeability, hydrogen peroxide (H2O2), superoxide radical (O2•-), methylglyoxal (MG), malondialdehyde (MDA), and increased activity of lipoxygenase (LOX). Salinity stress alone and the combination of salinity and Fe deficiency resulted in substantial accumulation of Na+ ions that impeded acquisition of essential nutrients. Taurine (100 and 200 mg L-1) notably improved osmotic adjustment and oxidative defense to diminish water imbalance and oxidative injury in plants under stress. These results suggest that exogenous taurine may serve as a promising means of mitigating the detrimental effects of salt stress and Fe deficiency in plants.

Nitrogen application improves salt tolerance of grape seedlings via regulating hormone metabolism

Salt stress is a dominant environmental factor that restricts the growth and yield of crops. Nitrogen is an essential mineral element for plants, regulates various physiological and biochemical processes, and has been reported to enhance salt tolerance in plants. However, the crosstalk between salt and nitrogen in grapes is not well understood. In this study, we found that nitrogen supplementation (0.01 and 0.1 mol L-1 NH4 NO3 ) significantly increased the accumulation of proline, chlorophyll, Na+ , NH4 + , and NO3 - , while it reduced the malondialdehyde content and inhibited photosynthetic performance under salt stress conditions (200 mmol L-1 NaCl). Further transcriptome and metabolome analyses showed that a total of 4890 differentially expressed genes (DEGs) and 753 differently accumulated metabolites (DAMs) were identified. Joint omics results revealed that plant hormone signal transduction pathway connected the DEGs and DAMs. In-depth analysis revealed that nitrogen supplementation increased the levels of endogenous abscisic acid, salicylic acid, and jasmonic acid by inducing the expression of 11, 4, and 13 genes related to their respective biosynthesis pathway. In contrast, endogenous indoleacetic acid content was significantly reduced due to the remarkable regulation of seven genes of its biosynthetic pathway. The modulation in hormone contents subsequently activated the differential expression of 13, 10, 12, and 29 genes of the respective downstream hormone signaling transduction pathways. Overall, all results indicate that moderate nitrogen supplementation could improve salt tolerance by regulating grape physiology and endogenous hormone homeostasis, as well as the expression of key genes in signaling pathways, which provides new insights into the interactions between mineral elements and salt stress.

Alleviating the adverse effects of salinity on Roselle plants by green synthesized nanoparticles

In the present study, an eco-friendly process was made for the rapid synthesis of silver nanoparticles using aqueous leaf extract of Hibiscus sabdariffa. The process was characterized by Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible and X-ray diffraction (XRD). These green silver nanoparticles (NPs) were used for mitigating the adverse effects of salinity on seed germination and growth parameters in plants. Accordingly, two experiments were conducted. In the first experiment, seven concentrations of green silver NPs and nine levels of NaCl:CaCl were apptoed on seeds for germination, and their effects were evaluated. In the second experiment, three concentrations of green silver NPs and NaCl were hypothesized to affect plant growth parameters. Seed germination, plant height, leaf, and root fresh and dry weights, as well as relative water content (RWC), decreased significantly under salt stress. However, green silver NPs intervened by alleviating the adverse effects of stress. Accordingly, green silver NPs were beneficial due to (1) activation of the antioxidant system by enhancing antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and superoxide dismutase (SOD); (2) increase in the amounts of proline, soluble sugars and carbohydrates for osmoprotection; (3) improvements in flavonoid and anthocyanin contents. Real-time PCR showed that flavonoid and anthocyanin contents increased because of higher expressions in chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and anthocyanidin synthase (ANS) genes. In conclusion, green silver NPs offered an eco-friendly application for further research on agricultural development.

Calcium-Rich Biochar Stimulates Salt Resistance in Pearl Millet (Pennisetum glaucum L.) Plants by Improving Soil Quality and Enhancing the Antioxidant Defense

Shrimp waste is rich in organic compounds and essential plant nutrients, e.g., calcium (Ca), and converting these wastes to organic fertilizer is important for environmental preservation and to achieve sustainable agricultural management. In the current study, Ca-rich biochar was prepared from shrimp wastes (SWB) by pyrolysis at 300 °C. We hypothesized that the Ca-rich biochar will help in solving the problem of plant growth in saline soil by reducing sodium (Na) uptake and mitigating oxidative stress. The current study aimed to investigate the effect of SWB on the quality of saline sandy soil and the mechanism of salt resistance in pearl millet (Pennisetum glaucum L.). Pearl millet plants were planted in saline sandy soil (10 dS m^-1) in wooden boxes (1.3 × 0.8 m size and 0.4 m height), and 5 doses (0, 1.0, 1.5, 2.0, and 2.5% (w/w)) of SWB were added. SWB application increased the soil quality and nutrient uptake by pearl millet plants. The highest rate of SWB increased the soil microbial biomass carbon and the activity of dehydrogenase enzyme by 43 and 47% compared to the control soil. SWB application reduced the uptake of sodium (Na⁺) and chloride (Cl^-) and increased the K/Na ratio in the leaf tissues. SWB addition significantly increased the activity of antioxidant enzymes, e.g., ascorbate peroxidase (APX), polyphenol oxidase (PPO), and pyrogallol peroxidases (PPX). The application of 2.5% SWB to the saline soil increased the soluble carbohydrates and proline in plant leaves by 75 and 60%, respectively, and reduced the malondialdehyde (MDA) by 32% compared to the control. SWB enhanced the antioxidant defense and mitigated oxidative stress by improving the synthesis of osmoprotectants, e.g., soluble carbohydrates and proline. Sandy saline soils in arid and semiarid areas suffer greatly from low organic matter contents, which reduces the soil quality and increases the risk of salt during plant growth. The high organic matter and calcium content (30%) in the shrimp waste-derived biochar improved the quality of the saline sandy soil, reduced the uptake of toxic salts, and increased the quality of the forage material. The addition of recycled shrimp waste to saline low-fertility soils improves soil productivity and is safe for soil health.

A manipulation of carotenoid metabolism influence biomass partitioning and fitness in tomato

Improving yield, nutritional value and tolerance to abiotic stress are major targets of current breeding and biotechnological approaches that aim at increasing crop production and ensuring food security. Metabolic engineering of carotenoids, the precursor of vitamin-A and plant hormones that regulate plant growth and response to adverse growth conditions, has been mainly focusing on provitamin A biofortification or the production of high-value carotenoids. Here, we show that the introduction of a single gene of the carotenoid biosynthetic pathway in different tomato cultivars induced profound metabolic alterations in carotenoid, apocarotenoid and phytohormones pathways. Alterations in isoprenoid- (abscisic acid, gibberellins, cytokinins) and non-isoprenoid (auxin and jasmonic acid) derived hormones together with enhanced xanthophyll content influenced biomass partitioning and abiotic stress tolerance (high light, salt, and drought), and it caused an up to 77% fruit yield increase and enhanced fruit's provitamin A content. In addition, metabolic and hormonal changes led to accumulation of key primary metabolites (e.g. osmoprotectants and antiaging agents) contributing with enhanced abiotic stress tolerance and fruit shelf life. Our findings pave the way for developing a new generation of crops that combine high productivity and increased nutritional value with the capability to cope with climate change-related environmental challenges.

Climate change regulated abiotic stress mechanisms in plants: a comprehensive review

Global climate change is identified as a major threat to survival of natural ecosystems. Climate change is a dynamic, multifaceted system of alterations in environmental conditions that affect abiotic and biotic components of the world. It results in alteration in environmental conditions such as heat waves, intensity of rainfall, CO₂ concentration and temperature that lead to rise in new pests, weeds and pathogens. Climate change is one of the major constraints limiting plant growth and development worldwide. It impairs growth, disturbs photosynthesis, and reduces physiological responses in plants. The variations in global climate have gained the attention of researchers worldwide, as these changes negatively affect the agriculture by reducing crop productivity and food security. With this background, this review focuses on the effects of elevated atmospheric CO₂ concentration, temperature, drought and salinity on the morphology, physiology and biochemistry of plants. Furthermore, this paper outlines an overview on the reactive oxygen species (ROS) production and their impact on the biochemical and molecular status of plants with increased climatic variations. Also additionally, different tolerance strategies adopted by plants to combat environmental adversities have been discussed.

Biochar and jasmonic acid application attenuates antioxidative systems and improves growth, physiology, nutrient uptake and productivity of faba bean (Vicia faba L.) irrigated with saline water

The effect of foliar treatment with jasmonic acid at 0.5 mM (JA) and biochar (15 ton ha^-1) as a soil amendment for the faba bean (Vicia faba L. Sakha 4) was studied under salinity conditions. Salt stress led to a significant decrease in leaf numbers, leaf areas and plants, chlorophyll content, relative water content, and yield parameters. In contrast, reactive oxygen species, the proline concentration, level of malondialdehyde, and amount of electrolyte leakage were noticeably increased during both seasons under salt levels of 1500 and 3000 ppm sodium chloride (NaCl). Also, enzyme activities (i.e., of superoxide dismutase, catalase, peroxidase, and glutathione reductase) were increased, especially under a high level of salinity stress (3000 ppm). Application of biochar, jasmonic acid, or biochar + jasmonic acid significantly reduced the catalase, superoxide dismutase, and glutathione reductase activities in salt-stressed plants to values approaching those of the control (unstressed) plants, especially under 1500 ppm of NaCl stress. Biochar and jasmonic acid treatments mitigated the damaging effects of salinity and improved the plant status as indicated by the plant height, leaf area, relative water content, and chlorophyll a and b concentrations. Moreover, biochar and jasmonic acid treatments of the salt-stressed plants enhanced plant productivity, number of flowers, number of seeds per plant, and weight of 100 seeds during two successive seasons. Overall, this study suggests that biochar or jasmonic acid treatments might be promising for mitigating the detrimental impact of salt stress on faba beans.

Jasmonates and Plant Salt Stress: Molecular Players, Physiological Effects, and Improving Tolerance by Using Genome-Associated Tools

Soil salinity is one of the most limiting stresses for crop productivity and quality worldwide. In this sense, jasmonates (JAs) have emerged as phytohormones that play essential roles in mediating plant response to abiotic stresses, including salt stress. Here, we reviewed the mechanisms underlying the activation and response of the JA-biosynthesis and JA-signaling pathways under saline conditions in Arabidopsis and several crops. In this sense, molecular components of JA-signaling such as MYC2 transcription factor and JASMONATE ZIM-DOMAIN (JAZ) repressors are key players for the JA-associated response. Moreover, we review the antagonist and synergistic effects between JA and other hormones such as abscisic acid (ABA). From an applied point of view, several reports have shown that exogenous JA applications increase the antioxidant response in plants to alleviate salt stress. Finally, we discuss the latest advances in genomic techniques for the improvement of crop tolerance to salt stress with a focus on jasmonates.