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

Sugarcane bagasse biochar boosts maize growth and yield in salt-affected soil by improving soil enzymatic activities

Salinization is a leading threat to soil degradation and sustainable crop production. The application of organic amendments could improve crop growth in saline soil. Thus, we assessed the impact of sugarcane bagasse (SB) and its biochar (SBB) on soil enzymatic activity and growth response of maize crop at three various percentages (0.5%, 1%, and 2% of soil) under three salinity levels (1.66, 4, and 8 dS m-1). Each treatment was replicated three times in a completely randomized block design with factorial settings. The results showed that SB and SBB can restore the impact of salinization, but the SBB at the 2% addition rate revealed promising results compared to SB. The 2% SBB significantly enhanced shoot length (23.4%, 26.1%, and 41.8%), root length (16.8%, 20.8%, and 39.0%), grain yield (17.6%, 25.1%, and 392.2%), relative water contents (11.2%, 13.1%, and 19.2%), protein (17.2%, 19.6%, and 34.9%), and carotenoid (16.3, 30.3, and 49.9%) under different salinity levels (1.66, 4, and 8 dS m-1, respectively). The 2% SBB substantially drop the Na+ in maize root (28.3%, 29.9%, and 22.4%) and shoot (36.1%, 37.2%, and 38.5%) at 1.66, 4, and 8 dS m-1. Moreover, 2% SBB is the best treatment to boost the urease by 110.1%, 71.7%, and 91.2%, alkaline phosphatase by 28.8%, 38.8%, and 57.6%, and acid phosphatase by 48.4%, 80.1%, and 68.2% than control treatment under 1.66, 4 and 8 dS m-1, respectively. Pearson analysis showed that all the growth and yield parameters were positively associated with the soil enzymatic activities and negatively correlated with electrolyte leakage and sodium. The structural equational model (SEM) showed that the different application percentage of amendments significantly influences the growth and physiological parameters at all salinity levels. SEM explained the 81%, 92%, and 95% changes in maize yield under 1.66, 4, and 8 dS m-1, respectively. So, it is concluded that the 2% SBB could be an efficient approach to enhance the maize yield by ameliorating the noxious effect of degraded saline soil.

Differential response of biochar in mitigating salinity stress in periwinkle (Catharanthus roseus L.) as an ornamental-medicinal plant species

To investigate the effect of various levels of salinity and biochar on the growth and biochemical traits of Catharanthus roseus L., a medicinal plant, a factorial experiment with three levels of biochar (0, 2, and 4%) and four levels of salinity (0, 1,000, 2,000, and 3,000 mg/kg soil) was conducted in pots under greenhouse conditions, in three replications, 36 pots, and 6 plants/plot. Salinity reduced the vegetative and reproductive growth and Ca and K uptake, and chlorophyll content of the plants, and increased the Na+, Cl-, electrolyte leakage, and antioxidant enzyme (SOD, CAT, GPX) activities. Biochar improved all the vegetative and reproductive growth and biochemical traits of Catharanthus roseus L. and enhanced soil fertility. The application of biochar at the rate of 2% at all four levels of NaCl reduced the activity of antioxidants and decreased electrolyte leakage, reflecting the alleviation of salinity effects and the retention of cell health for survival. The application of biochar 2% was more effective than biochar 4% in alleviating salinity stress. Therefore, by using 2% biochar, it is possible to improve saline soils (soils containing 1,000 or 2,000 mg/kg NaCl) and grow periwinkle ornamental-medicinal plant in it. The plants showed acceptable performance at salinity levels of 1,000 or 2,000 mg/kg with biochar 2%.

Improvement of morphophysiological and anatomical attributes of plants under abiotic stress conditions using plant growth-promoting bacteria and safety treatments

Drought and salinity are the major abiotic stress factors negatively affecting the morphophysiological, biochemical, and anatomical characteristics of numerous plant species worldwide. The detrimental effects of these environmental factors can be seen in leaf and stem anatomical structures including the decrease in thickness of cell walls, palisade and spongy tissue, phloem and xylem tissue. Also, the disintegration of grana staking, and an increase in the size of mitochondria were observed under salinity and drought conditions. Drought and salt stresses can significantly decrease plant height, number of leaves and branches, leaf area, fresh and dry weight, or plant relative water content (RWC%) and concentration of photosynthetic pigments. On the other hand, stress-induced lipid peroxidation and malondialdehyde (MDA) production, electrolyte leakage (EL%), and production of reactive oxygen species (ROS) can increase under salinity and drought conditions. Antioxidant defense systems such as catalase, peroxidase, glutathione reductase, ascorbic acid, and gamma-aminobutyric acid are essential components under drought and salt stresses to protect the plant organelles from oxidative damage caused by ROS. The application of safe and eco-friendly treatments is a very important strategy to overcome the adverse effects of drought and salinity on the growth characteristics and yield of plants. It is shown that treatments with plant growth-promoting bacteria (PGPB) can improve morphoanatomical characteristics under salinity and drought stress. It is also shown that yeast extract, mannitol, proline, melatonin, silicon, chitosan, α-Tocopherols (vitamin E), and biochar alleviate the negative effects of drought and salinity stresses through the ROS scavenging resulting in the improvement of plant attributes and yield of the stressed plants. This review discusses the role of safety and eco-friendly treatments in alleviating the harmful effects of salinity and drought associated with the improvement of the anatomical, morphophysiological, and biochemical features in plants.

Alpha lipoic acid mitigates adverse impacts of drought stress on growth and yield of mungbean: photosynthetic pigments, and antioxidative defense mechanism

Context

Exogenous use of potential organic compounds through different modes is a promising strategy for the induction of water stress tolerance in crop plants for better yield.

Aims

The present study aimed to explore the potential role of alpha-lipoic acid (ALA) in inducing water stress tolerance in mungbean lines when applied exogenously through various modes.

Methods

The experiment was conducted in a field with a split-plot arrangement, having three replicates for each treatment. Two irrigation regimes, including normal and reduced irrigation, were applied. The plants allocated to reduced irrigation were watered only at the reproductive stage. Three levels of ALA (0, 0.1, 0.15 mM) were applied through different modes (seed priming, foliar or priming+foliar).

Key results

ALA treatment through different modes manifested higher growth under reduced irrigation (water stress) and normal irrigation. Compared to the other two modes, the application of ALA as seed priming was found more effective in ameliorating the adverse impacts of water stress on growth and yield associated with their better content of leaf photosynthetic pigments, maintenance of plant water relations, levels of non-enzymatic antioxidants, improved activities of enzymatic antioxidants, and decreased lipid peroxidation and H2O2 levels. The maximum increase in shoot fresh weight (29% and 28%), shoot dry weight (27% and 24%), 100-grain weight (24% and 23%) and total grain yield (20% and 21%) in water-stressed mungbean plants of line 16003 and 16004, respectively, was recorded due to ALA seed priming than other modes of applications.

Conclusions

Conclusively, 0.1 and 0.15 mM levels of ALA as seed priming were found to reduce the adverse impact of water stress on mungbean yield that was associated with improved physio-biochemical mechanisms.

Implications

The findings of the study will be helpful for the agriculturalists working in arid and semi-arid regions to obtain a better yield of mungbean that will be helpful to fulfill the food demand in those areas to some extent.

Biochar enhances the growth and physiological characteristics of Medicago sativa, Amaranthus caudatus and Zea mays in saline soils

Biochar is a promising solution to alleviate the negative impacts of salinity stress on agricultural production. Biochar derived from food waste effect was investigated on three plant species, Medicago sativa, Amaranthus caudatus, and Zea mays, under saline environments. The results showed that biochar improved significantly the height by 30%, fresh weight of shoot by 35% and root by 45% of all three species compared to control (saline soil without biochar adding), as well as enhanced their photosynthetic pigments and enzyme activities in soil. This positive effect varied significantly between the 3 plants highlighting the importance of the plant-biochar interactions. Thus, the application of biochar is a promising solution to enhance the growth, root morphology, and physiological characteristics of plants under salt-induced stress.

Physio-Biochemical, Anatomical, and Molecular Analysis of Resistant and Susceptible Wheat Cultivars Infected with TTKSK, TTKST, and TTTSK Novel Puccinia graminis Races

Stem rust, caused by Puccinia graminis f.sp. tritici, is one of the most dangerous rust diseases on wheat. Through physiological, biochemical, and molecular analysis, the relationship between the change in resistance of 15 wheat cultivars to stem rust disease and the response of 41 stem rust resistance genes (Sr,s) as well as TTKSK, TTKST, and TTTSK races was explained. Some cultivars and Sr genes, such as Gemmeiza-9, Gemmeiza-11, Sids-13, Sakha-94, Misr-1, Misr-2, Sr31, and Sr38, became susceptible to infection. Other new cultivars include Mir-3 and Sakha-95, and Sr genes 13, 37, 40, GT, and FR*2/SRTT3-SRTT3-SR10 remain resistant. Some resistance genes have been identified in these resistant cultivars: Sr2, Sr13, Sr24, Sr36, and Sr40. Sr31 was not detected in any cultivars. Reactive oxygen species such as hydrogen peroxide and superoxide, enzymes activities (catalase, peroxidase, and polyphenoloxidase), and electrolyte leakage were increased in the highly susceptible cultivars, while they decreased in the resistant ones. Anatomical characteristics such as the thickness of the epidermis, ground tissue, phloem tissue and vascular bundle diameter in the midrib were decreased in susceptible cultivars compared with resistant cultivars. Our results indicated that some races (TTKSK, TTKST, and TTTSK) appeared for the first time in Egypt and many other countries, which broke the resistant cultivars. The wheat rust breeding program must rely on land races and pyramiding genes in order to develop new resistance genes that will survive for a very long time.

Evaluation of Five Chrysanthemum morifolium Cultivars against Leaf Blight Disease Caused by Alternaria alternata at Rooting and Seedling Growth Stages

During the winter of 2018, leaf blight on florist's daisy (Chrysanthemum morifolium L.) was noticed in Egypt. The disease, which was identified as caused by Alternaria alternata, was widely spread and led to serious damage for the exportation sector of this crop. Therefore, a study was conducted to better understand what can be conducted to minimize the problem in the future. Isolates were gathered and evaluated on five chrysanthemum cultivars (i.e., 'Feeling Green Dark', 'Talitha', 'Chrystal Regan', 'Arctic queen', and 'Podolsk Purple') grown in a greenhouse. The objectives were to isolate and identify the phytopathogen and detect the resistant degree of these cultivars with emphasis on the early growth stages of the crop. The results showed that 'Podolsk Purple' was the most resistant cultivar against the different isolates during the rooting and seedling growth stages. 'Chrystal Regan' was very susceptible to the different isolates. In addition, the isolate from 'Feeling Green Dark' was the strongest, which negatively affected the chlorophyll content and its fluorescence parameters besides other measured vegetative and anatomical features. The findings indicated that the best anatomical characters of the stem and leaf, like the thickness of cuticle and cortex, stem diameter, xylem vessel diameter, and thickness of epidermis as well as lamina thickness were recorded in the 'Podolsk Purple' cultivar. This study highlighted that by using the right cultivars, chrysanthemum can be cultivated during the winter season under Egyptian conditions. These results can be a part of solution to overcome the leaf blight caused by A. alternata on chrysanthemum during the early growing stages.

Secreted Peptide SpPIP1 Modulates Disease Resistance and Salt Tolerance in Tomato

Tomato is a globally important horticultural and economic crop, but its productivity is severely affected by various stresses. Plant small secretory peptides have been identified as crucial mediators in plant resistance. Here, we conducted a comparative transcriptome analysis and identified the prePIP1 gene from Solanum pimpinellifolium (SpprePIP1), as an ortholog of Arabidopsis prePIP1 encoding the precursor protein of PAMP-induced SSP 1. The expression level of SpprePIP1 is transcriptionally induced in tomato upon infection with Phytophthora infestans (P. infestans), the pathogen responsible for late blight. Overexpression of SpprePIP1 resulted in enhanced tomato resistance to P. infestans. In addition, exogenous application of SpPIP1, whether through spraying or irrigation, improved tomato resistance by enhancing the transcript accumulations of pathogenesis-related proteins, as well as reactive oxygen species and the jasmonic acid (JA) levels. Integrated analysis of transcriptomics and metabolomics revealed the potential contributions of JA and phenylpropanoid biosynthesis to SpPIP1-induced tomato immunity. Additionally, SpPIP1 may strengthen tomato resistance to salt stress through the ABA signaling pathway. Overall, our findings demonstrate that SpPIP1 positively regulates tomato tolerance to P. infestans and salt stress, making it a potential plant elicitor for crop protection in an environmentally friendly way.

Jasmonic acid boosts the salt tolerance of kidney beans (Phaseolus vulgaris L.) by upregulating its osmolytes and antioxidant mechanism

As a lipid-derived compound, jasmonic acid (JA) regulates growth and defense against environmental stresses. An exogenous foliar JA application was investigated in our study (HA; 0.5 mM) on kidney bean plants (Phaseolus vulgaris L.) grown under different salinity stress concentrations (0, 75, and 150 mM NaCl). According to the results, salt concentrations were related to an increase in malondialdehyde (MDA) levels, whereas they declined the chlorophyll content index. In contrast, JA application decreased the level of MDA but increased the chlorophyll content index. Moreover, increasing salinity levels increased proline, phenolic compounds, flavonoids, free amino acid concentrations, and shikimic acid concentrations, as well as the activities of polyphenol oxidase (PPO), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD). In addition, JA applications further increased their concentrations with increasing salinity stress levels. JA application increases salt-induced osmolytes and non-enzymatic antioxidants while increasing enzymatic antioxidant activity, suggesting kidney beans have a strong antioxidant mechanism, which can adapt to salinity stress. Our results showed that exogenous JA foliar applications could enhance the salt tolerance ability of kidney bean plants by upregulating their antioxidant mechanism and osmolytes.

Effects of Drying Treatments on Nutritional Compositions, Volatile Flavor Compounds, and Bioactive Substances of Broad Beans

In this study, different drying methods, including hot air drying, sun drying, and freeze drying were employed to dry fresh broad beans. The nutritional composition, volatile organic components and bioactive substances of the dried broad beans were systematically compared. The results indicated significant differences (p < 0.05) in nutritional composition, such as protein and soluble sugar content. Among the 66 identified volatile organic compounds, freeze drying and hot air drying significantly promote the production of alcohols and aldehydes, while sun drying effectively preserves esters. In terms of bioactive substances, broad beans dried by freeze drying exhibit the highest total phenol content as well as the strongest antioxidant capacity and gallic acid, followed by sun drying. The chemometric analysis revealed that the bioactive compounds in broad beans dried by three different methods were primarily composed of flavonoids, organic acids, and amino acids with significant differentiation. Notably, freeze-dried and sun-dried broad beans exhibited a higher concentration of differential substances.

Solid and modified biochars mitigate root cell lignification and improve nutrients uptake in mint plants under fluoride and cadmium stresses

Lignification is a physiological process that reduces pollutants' entrance into plant root cells via blocking apoplastic pathways. The closure of apoplastic pathways can also decrease the nutrients' uptake by roots. Application of biochar as an efficient soil amendment might be useful in increasing nutrients influx into root cells by decreasing lignification. Therefore, this experiment was performed to examine the conceivable effects of biochar forms [solid and chemically altered biochars with H₂O_2, KOH and H₃PO₄ (25 g biochar forms kg^-1 soil)] on modifying lignification process and nutrients uptake by mint (Mentha crispa L.) plants under toxicity of cadmium and fluoride. The biochar treatments boosted plant root growth and activity as well as the real content and maximum sorption capacity of Zn, Fe, Mg, and Ca under stressful conditions. In contrast, biochar treatments increased root cell viability and reduced fluoride and cadmium contents, and oxidative damages under stressful conditions. The biochar treatments decreased the activity of phenylalanine ammonia-lyase and peroxidase enzymes under toxic conditions, which led to a decrease in the contents of lignin and its monomers (p-hydroxybenzaldehyde, guaiacyl, and syringaldehyde) in the roots. Solid biochar was less effective than engineered biochars in reducing root cell lignification. Therefore, addition of biochar forms to the soil could be an effective way to reduce root cell lignification and enhance nutrients uptake by plants under cadmium and fluoride toxicities.

The critical role of biochar to mitigate the adverse impacts of drought and salinity stress in plants

Drought stress (DS) is a potential abiotic stress that is substantially reducing crop productivity across the globe. Likewise, salinity stress (SS) is another serious abiotic stress that is also a major threat to global crop productivity. The rapid climate change increased the intensity of both stresses which pose a serious threat to global food security; therefore, it is urgently needed to tackle both stresses to ensure better crop production. Globally, different measures are being used to improve crop productivity under stress conditions. Among these measures, biochar (BC) has been widely used to improve soil health and promote crop yield under stress conditions. The application of BC improves soil organic matter, soil structure, soil aggregate stability, water and nutrient holding capacity, and the activity of both beneficial microbes and fungi, which leads to an appreciable increase in tolerance to both damaging and abiotic stresses. BC biochar protects membrane stability, improves water uptake, maintains nutrient homeostasis, and reduces reactive oxygen species production (ROS) through enhanced antioxidant activities, thereby substantially improving tolerance to both stresses. Moreover, BC-mediated improvements in soil properties also substantially improve photosynthetic activity, chlorophyll synthesis, gene expression, the activity of stress-responsive proteins, and maintain the osmolytes and hormonal balance, which in turn improve tolerance against osmotic and ionic stresses. In conclusion, BC could be a promising amendment to bring tolerance against both drought and salinity stresses. Therefore, in the present review, we have discussed various mechanisms through which BC improves drought and salt tolerance. This review will help readers to learn more about the role of biochar in causing drought and salinity stress in plants, and it will also provide new suggestions on how this current knowledge about biochar can be used to develop drought and salinity tolerance.

Applied Selenium as a Powerful Antioxidant to Mitigate the Harmful Effects of Salinity Stress in Snap Bean Seedlings

Selenium (Se) plays several significant roles in regulating growth, development and plant responses to various abiotic stresses. However, its influence on sulfate transporters (SULTRS) and achieving the harmony with other salt-tolerance features is still limited in the previous literatures. This study elucidated the effect of Se supplementation (5, 10 and 20 µM) on salt-stressed (50 mM NaCl) snap bean seedlings. Generally, the results indicated that Se had dual effects on the salt stressed seedlings according to its concentration. At a low level (5 µM), plants demonstrated a significant improvement in shoot (13.8%) and root (22.8%) fresh weight, chlorophyll a (7.4%), chlorophyll b (14.7%), carotenoids (23.2%), leaf relative water content (RWC; 8.5%), proline (17.2%), total soluble sugars (34.3%), free amino acids (FAA; 18.4%), K (36.7%), Ca (33.4%), K/Na ratio (77.9%), superoxide dismutase (SOD; 18%), ascorbate peroxidase (APX;12.8%) and guaiacol peroxidase (G-POX; 27.1%) compared to the untreated plants. Meanwhile, most of these responses as well as sulfur (S), Se and catalase (CAT) were obviously decreased in parallel with increasing the applied Se up to 20 µM. The molecular study revealed that three membrane sulfate transporters (SULTR1, SULTR2 and SULTR 3) in the root and leaves and salinity responsive genes (SOS1, NHX1 and Osmotin) in leaves displayed different expression patterns under various Se treatments. Conclusively, Se at low doses can be beneficial in mitigating salinity-mediated damage and achieving the functioning homeostasis to tolerance features.

Improving the Tolerance to Salinity Stress in Lettuce Plants (Lactuca sativa L.) Using Exogenous Application of Salicylic Acid, Yeast, and Zeolite

Salinity is among the most limiting factors of crop production worldwide. This study aims to investigate the influence of the exogenous application of zeolite, yeast, and salicylic acid in alleviating the negative effect of salt stress under field conditions. Lettuce plants (Lactuca sativa L. cv. Batavia) were tested in a split-plot arrangement replicated three times. The salt stress was applied as a whole-plot factor in the concentrations (0 mM, 50 mM, 100 mM, and 150 mM NaCl). After 28 days of sowing, the plants were sprayed twice during the foliage growth with (control, salicylic acid 0.02%, yeast extract 3%, and zeolite 0.5%) as a split-plot factor. The length of roots and shoots, the number and area of leaves, and the biomass accumulation (dry and fresh weights) were measured 50 days after sowing. The concentrations of total soluble sugars, proline, Chlorophylls a and b in leaves have also been quantified. Salt stress significantly reduced the growth and the total chlorophyll of the lettuce plants (p < 0.05) and increased their proline and sugar contents’. Zeolite application improved the growth of lettuce at 0 and 50 mM NaCl, but at the highest salinity level only the number of leaves was improved by 15%. At a mild salinity stress, the application of salicylic acid has significantly (p < 0.05) increased the root length, height of plant, chlorophyll, and proline contents. Regarding the high stress levels (100 and 150 mM NaCl), yeast application showed the best tolerance to salinity stress by improving significantly most of the growth parameters (p < 0.05) but with lower proline, sugar, and chlorophyll contents. In general, foliar spray of yeast extract may offer a good alternative source of nutrients through leaves, leading to a better tolerance of the high salt stress exerted on roots.

Folic Acid Reinforces Maize Tolerance to Sodic-Alkaline Stress through Modulation of Growth, Biochemical and Molecular Mechanisms

The mechanism by which folic acid (FA) or its derivatives (folates) mediates plant tolerance to sodic-alkaline stress has not been clarified in previous literature. To apply sodic-alkaline stress, maize seedlings were irrigated with 50 mM of a combined solution (1:1) of sodic-alkaline salts (NaHCO₃ and Na₂CO₃; pH 9.7). Maize seedlings under stressed and non-stressed conditions were sprayed with folic acid (FA) at 0 (distilled water as control), 0.05, 0.1, and 0.2 mM. Under sodic-alkaline stress, FA applied at 0.2 mM significantly improved shoot fresh weight (95%), chlorophyll (Chl a (41%), Chl b (57%), and total Chl (42%)), and carotenoids (27%) compared to the untreated plants, while root fresh weight was not affected compared to the untreated plants. This improvement was associated with a significant enhancement in the cell-membrane stability index (CMSI), relative water content (RWC), free amino acids (FAA), proline, soluble sugars, K, and Ca. In contrast, Na, Na/K ratio, H₂O₂, malondialdehyde (MDA), and methylglycoxal (MG) were significantly decreased. Moreover, seedlings treated with FA demonstrated significantly higher activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), and ascorbate peroxidase (APX) compared to the untreated plants. The molecular studies using RT-qPCR demonstrated that FA treatments, specifically at 0.2 mM, enhanced the K⁺/Na⁺ selectivity and the performance of photosynthesis under alkaline-stress conditions. These responses were observed through up-regulation of the expression of the high-affinity potassium-transporter protein (ZmHKT1), the major core protein of photosystem II (D2-Protein), and the activity of the first enzyme of carbon fixation cycle in C4 plants (PEP-case) by 74, 248, and 225% over the untreated plants, respectively. Conversely, there was a significant down-regulation in the expression ZmSOS1 and ZmNHX1 by 48.2 and 27.8%, respectively, compared to the untreated plants.

Overview of the use of biochar from main cereals to stimulate plant growth

The total global food demand is expected to increase up to 50% between 2010 and 2050; hence, there is a clear need to increase plant productivity with little or no damage to the environment. In this respect, biochar is a carbon-rich material derived from the pyrolysis of organic matter at high temperatures with a limited oxygen supply, with different physicochemical characteristics that depend on the feedstock and pyrolysis conditions. When used as a soil amendment, it has shown many positive environmental effects such as carbon sequestration, reduction of greenhouse gas emissions, and soil improvement. Biochar application has also shown huge benefits when applied to agri-systems, among them, the improvement of plant growth either in optimal conditions or under abiotic or biotic stress. Several mechanisms, such as enhancing the soil microbial diversity and thus increasing soil nutrient-cycling functions, improving soil physicochemical properties, stimulating the microbial colonization, or increasing soil P, K, or N content, have been described to exert these positive effects on plant growth, either alone or in combination with other resources. In addition, it can also improve the plant antioxidant defenses, an evident advantage for plant growth under stress conditions. Although agricultural residues are generated from a wide variety of crops, cereals account for more than half of the world's harvested area. Yet, in this review, we will focus on biochar obtained from residues of the most common and relevant cereal crops in terms of global production (rice, wheat, maize, and barley) and in their use as recycled residues to stimulate plant growth. The harvesting and processing of these crops generate a vast number and variety of residues that could be locally recycled into valuable products such as biochar, reducing the waste management problem and accomplishing the circular economy premise. However, very scarce literature focused on the use of biochar from a crop to improve its own growth is available. Herein, we present an overview of the literature focused on this topic, compiling most of the studies and discussing the urgent need to deepen into the molecular mechanisms and pathways involved in the beneficial effects of biochar on plant productivity.

Jasmonic acid pretreatment improves salt tolerance of wheat by regulating hormones biosynthesis and antioxidant capacity

Salt stress is a severe environmental factor that detrimentally affects wheat growth and production worldwide. Previous studies illustrate that exogenous jasmonic acid (JA) significantly improved salt tolerance in plants. However, little is known about the underlying molecular mechanisms of JA induced physiochemical changes in wheat seedlings under salt stress conditions. In this study, biophysiochemical and transcriptome analysis was conducted to explore the mechanisms of exogenous JA induced salt tolerance in wheat. Exogenous JA increased salt tolerance of wheat seedlings by alleviating membrane lipid oxidation, improving root morphology, enhancing the contents of ABA, JA and SA and increasing relative water content. In the RNA-seq profiles, we identified a total of 54,263 unigenes and 1,407 unigenes showed differentially expressed patterns in JA pretreated wheat seedlings exposed to salt stress comparing to those with salt stress alone. Subsequently, gene ontology (GO) and KEGG pathway enrichment analysis characterized that DEGs involved in linoleic acid metabolism and plant hormone signal transduction pathways were up-regulated predominantly in JA pretreated wheat seedlings exposed to salt stress. We noticed that genes that involved in antioxidative defense system and that encoding transcription factors were mainly up- or down-regulated. Moreover, SOD, POD, CAT and APX activities were increased in JA pretreated wheat seedlings exposed to salt stress, which is in accordance with the transcript profiles of the relevant genes. Taken together, our results demonstrate that the genes and enzymes involved in physiological and biochemical processes of antioxidant system, plant hormones and transcriptional regulation contributed to JA-mediated enhancement of salt tolerance in wheat. These findings will facilitate the elucidation of the potential molecular mechanisms associated with JA-dependent amelioration of salt stress in wheat and lay theoretical foundations for future studies concerning the improvement of plant tolerance to abiotic environmental stresses.

Physiological Studies and Ultrastructure of Vigna sinensis L. and Helianthus annuus L. under Varying Levels of Nitrogen Supply

This experiment was conducted to investigate the effects of different nitrogen fertilizers (potassium nitrate and/or urea) on shoot parameters, relative growth rate, net assimilation rate, and nitrogen fractions, as well as to conduct transmission electron microscopy, of Vigna sinensis L. (cowpea) and Helianthus annuus L. (sunflower) leaves. A general improvement was recorded in the shoot parameters of the two plants, except for a decrease in the net assimilation rate by treatment of the two plants with 100% potassium nitrate plus 100% urea. The total nitrogen, insoluble protein, and total soluble nitrogen generally decreased in cowpea shoots from the treatments but increased in case of cowpea roots and sunflower shoots and roots. The examination of the ultrastructure changes in cowpea leaves confirmed the presence of two starch granules (in response to 100% potassium nitrate, 100% potassium nitrate plus 100% urea, and the control) and three granules (in response to 50% potassium nitrate plus 50% urea) and the disappearance of the starch granules (in response to 100% urea). Despite the starch granules not being detected in the leaves of the untreated sunflower, the treated plant showed the appearance of the highest number after treatment with 50% potassium nitrate plus 50% urea (2) and the most cell size with the 100% potassium nitrate treatment. Generally, our findings demonstrated that fertilization with 50% potassium nitrate plus 50% urea has the best influence on the growth parameters and nitrogen content in the two plants, but the magnitude of response was more pronounced in case of cowpea plants.

Biochar/vermicompost promotes Hybrid Pennisetum plant growth and soil enzyme activity in saline soils

Soil salinity has become a major threat to land degradation worldwide. The application of organic amendments is a promising alternative to restore salt-degraded soils and alleviate the deleterious effects of soil salt ions on crop growth and productivity. The aim of present study was to explore the potential impact of biochar and vermicompost, applied individually or in combination, on soil enzyme activity and the growth, yield and quality of Hybrid Pennisetum plants suffered moderate salt stress (5.0 g kg^-1 NaCl in the soil). Our results showed that biochar and/or vermicompost promoted Na⁺ exclusion and K⁺ accumulation, relieved stomatal limitation, increased leaf pigment contents, enhanced electron transport efficiency and net photosynthesis, improved root activity, and minimized the oxidative damage in Hybrid Pennisetum caused by soil salinity stress. In addition, soil enzymes were also activated by biochar and vermicompost. These amendments increased the biomass and crude protein content, and decreased the acid detergent fiber and neutral detergent fiber contents in salt-stressed Hybrid Pennisetum. Biochar and vermicompost addition increased the biomass and quality of Hybrid Pennisetum due to the direct effects related to plant growth parameters and the indirect effects via soil enzyme activity. Finally, among the different treatments, the use of vermicompost showed better results than biochar alone or the biochar-compost combination did, suggesting that the addition of vermicompost to the soil is an effective and valuable method for reclamation of salt-affected soils.

Folic Acid Confers Tolerance against Salt Stress-Induced Oxidative Damages in Snap Beans through Regulation Growth, Metabolites, Antioxidant Machinery and Gene Expression

Although the effect of folic acid (FA) and its derivatives (folates) have been extensively studied in humans and animals, their effects are still unclear in most plant species, specifically under various abiotic stress conditions. Here, the impact of FA as a foliar application at 0, 0.1, and 0.2 mM was studied on snap bean seedlings grown under non-saline and salinity stress (50 mM NaCl) conditions. The results indicated that under salinity stress, FA-treated plants revealed a significant (p ≤ 0.05) increase in growth parameters (fresh and dry weight of shoot and root). A similar trend was observed in chlorophyll (Chl b), total chlorophyll, carotenoids, leaf relative water content (RWC), proline, free amino acids (FAA), soluble sugars, cell membrane stability index (CMSI), and K, Ca, and K/Na ratio compared to the untreated plants. In contrast, a significant decrease was observed in Na and salinity-induced oxidative damage as indicated by reduced H₂O₂ production (using biochemical and histochemical detection methods) and rate of lipid peroxidation (malondialdehyde; MDA). This enhancement was correlated by increasing the activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (G-POX), and ascorbate peroxidase (APX). Gene expression analyses conducted using qRT-PCR demonstrated that genes coding for the Na⁺/H⁺ antiporter protein Salt Overly Sensitive 1 (SOS1), the tonoplast-localized Na⁺/H⁺ antiporter protein (NHX1), and the multifunctional osmotic protective protein (Osmotin) were significantly up-regulated in the FA-treated plants under both saline and non-saline treatments. Generally, treatment with 0.2 mM FA was more potent than 0.1 mM and can be recommended to improve snap bean tolerance to salinity stress.

Alpha Lipoic Acid as a Protective Mediator for Regulating the Defensive Responses of Wheat Plants against Sodic Alkaline Stress: Physiological, Biochemical and Molecular Aspects

Recently, exogenous α-Lipoic acid (ALA) has been suggested to improve the tolerance of plants to a wide array of abiotic stresses. However, there is currently no definitive data on the role of ALA in wheat plants exposed to sodic alkaline stress. Therefore, this study was designed to evaluate the effects of foliar application by ALA at 0 (distilled water as control) and 20 µM on wheat seedlings grown under sodic alkaline stress (50 mM 1:1 NaHCO₃ & Na₂CO₃; pH 9.7. Under sodic alkaline stress, exogenous ALA significantly (p ≤ 0.05) improved growth (shoot fresh and dry weight), chlorophyll (Chl) a, b and Chl a + b, while Chl a/b ratio was not affected. Moreover, leaf relative water content (RWC), total soluble sugars, carotenoids, total soluble phenols, ascorbic acid, K and Ca were significantly increased in the ALA-treated plants compared to the ALA-untreated plants. This improvement was concomitant with reducing the rate of lipid peroxidation (malondialdehyde, MDA) and H₂O₂. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) demonstrated greater activity in the ALA-treated plants compared to the non-treated ones. Conversely, proline, catalase (CAT), guaiacol peroxidase (G-POX), Na and Na/K ratio were significantly decreased in the ALA-treated plants. Under sodic alkaline stress, the relative expression of photosystem II (D2 protein; PsbD) was significantly up-regulated in the ALA treatment (67% increase over the ALA-untreated plants); while Δ pyrroline-5-carboxylate synthase (P5CS), plasma membrane Na⁺/H⁺ antiporter protein of salt overly sensitive gene (SOS1) and tonoplast-localized Na⁺/H⁺ antiporter protein (NHX1) were down-regulated by 21, 37 and 53%, respectively, lower than the ALA-untreated plants. These results reveal that ALA may be involved in several possible mechanisms of alkalinity tolerance in wheat plants.

Effect of Salt Stress and Foliar Application of Salicylic Acid on Morphological, Biochemical, Anatomical, and Productivity Characteristics of Cowpea (Vigna unguiculata L.) Plants

The present study aimed to investigate the impact of salinity on vegetative growth, chemical constituents, and yields of cowpeas (Vigna unguiculata) and the possible benefits of salicylic acid (SA) on these plants after damage from salinity. To achieve these objectives, two pot experiments were carried out at the Faculty of Agriculture, Al-Azhar University, Egypt, during the two growing seasons of 2019 and 2020. The results revealed that salinity significantly decreased, and SA treatment substantially increased the plant height, number of compound leaves, number of internodes per plant, fresh weights of leaves and stems, productivity, photosynthetic pigments content, and concentrations of nitrogen (N), phosphorus (P), and potassium (K) of the cowpea plants compared with the control. The anatomical structure of stems and leaves of the plants were also investigated, and it was found that positive variations in the anatomical structure of the median portion of the main stems and blades of mature foliage leaves were detected in the stressed and SA-treated plants. In conclusion, SA treatment increased the salt stress tolerance of cowpea plants by improving the morphological and physiological attributes of the plants.

Exogenous Application of Alpha-Lipoic Acid Mitigates Salt-Induced Oxidative Damage in Sorghum Plants through Regulation Growth, Leaf Pigments, Ionic Homeostasis, Antioxidant Enzymes, and Expression of Salt Stress Responsive Genes

In plants, α-Lipoic acid (ALA) is considered a dithiol short-chain fatty acid with several strong antioxidative properties. To date, no data are conclusive regarding its effects as an exogenous application on salt stressed sorghum plants. In this study, we investigated the effect of 20 µM ALA as a foliar application on salt-stressed sorghum plants (0, 75 and 150 mM as NaCl). Under saline conditions, the applied-ALA significantly (p ≤ 0.05) stimulated plant growth, indicated by improving both fresh and dry shoot weights. A similar trend was observed in the photosynthetic pigments, including Chl a, Chl b and carotenoids. This improvement was associated with an obvious increase in the membrane stability index (MSI). At the same time, an obvious decrease in the salt induced oxidative damages was seen when the concentration of H2O2 and malondialdehyde (MDA) was reduced in the salt stressed leaf tissues. Generally, ALA-treated plants demonstrated higher antioxidant enzyme activity than in the ALA-untreated plants. A moderate level of salinity (75 mM) induced the highest activities of superoxide dismutase (SOD), guaiacol peroxidase (G-POX), and ascorbate peroxidase (APX). Meanwhile, the highest activity of catalase (CAT) was seen with 150 mM NaCl. Interestingly, applied-ALA led to a substantial decrease in the concentration of both Na and the Na/K ratio. In contrast, K and Ca exhibited a considerable increase in this respect. The role of ALA in the regulation of K+/Na+ selectivity under saline condition was confirmed through a molecular study (RT-PCR). It was found that ALA treatment downregulated the relative gene expression of plasma membrane (SOS1) and vacuolar (NHX1) Na+/H+ antiporters. In contrast, the high-affinity potassium transporter protein (HKT1) was upregulated.

Roles of Exogenous α-Lipoic Acid and Cysteine in Mitigation of Drought Stress and Restoration of Grain Quality in Wheat

Cysteine (Cys) and α-lipoic acid (ALA) are naturally occurring antioxidants (sulfur-containing compounds) that can protect plants against a wide spectrum of environmental stresses. However, up to now, there are no conclusive data on their integrative roles in mitigation of drought stress in wheat plants. Here, we studied the influence of ALA at 0.02 mM (grain dipping pre-cultivation treatment) and Cys (25 and 50 ppm as a foliar application) under well watered and deficit irrigation (100% and 70% of recommended dose). The results showed that deficit irrigation markedly caused obvious cellular oxidative damage as indicated by elevating the malondialdehyde (MDA) and hydrogen peroxide content (H₂O₂). Moreover, water stressed plants exhibited multiple changes in physiological metabolism, which affected the quantitative and qualitative variables of grain yield. The enzymatic antioxidants, including superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) were improved by Cys application. SOD and APX had the same response when treated with ALA, but CAT and POX did not. Moreover, both studied molecules stimulated chlorophyll (Chl) and osmolytes' biosynthesis. In contrast, the Chl a/b ratio was decreased, while flavonoids were not affected by either of the examined molecules. Interestingly, all above-mentioned changes were associated with an improvement in the scavenging capacity of reactive oxygen species (ROS), leaf relative water content (RWC), grain number, total grain yield, weight of 1000 kernels, gluten index, falling number, and alveographic parameters (P, W, and P/L values). Furthermore, heatmap plot analysis revealed several significant correlations between different studied parameters, which may explore the importance of applied Cys and ALA as effective compounds in wheat cultivation under water deficit conditions.

Interactive Effects of Arbuscular Mycorrhizal Inoculation with Nano Boron, Zinc, and Molybdenum Fertilization on Stevioside Contents of Stevia (Stevia rebaudiana, L.) Plants

Stevia (Stevia rebaudiana, L.) is receiving increasing global interest as a diabetes-focused herb associated with zero-calorie stevioside sweetener glycoside production. This study was conducted to determine whether the arbuscular mycorrhiza (AM), as a biofertilizer integrated with nano boron (B), zinc (Zn), and molybdenum (Mo), would improve stevia growth and stevioside content. A factorial experiment with four replicates was conducted to evaluate the effect of AM at 0, 150, and 300 spore/g soil and three nano microelements B at 100 mg/L, Zn at 100 mg/L, and Mo at 40 mg/L on growth performance, stevioside, mineral contents, and biochemical contents of stevia. Results indicated that the combination of AM at 150 and B at 100 mg/L significantly increased plant height, number of leaves, fresh and dry-stem, and herbal g/plant during the 2019 and 2020 growing seasons. Chlorophyll content was increased by the combination between AM at 150 spore/g soil and B at 100 mg/L during both seasons. Stevioside content in leaves was increased by AM at 150 spore/g soil and B at 100 mg/L during the second season. In addition, N, P, K, Zn, and B in the leaf were increased by applying the combination of AM and nano microelements. Leaf bio constituent contents were increased with AM at 150 spore/g soil and B at 100 mg/L during both seasons. The application of AM and nano B can be exploited for high growth, mineral, and stevioside contents as a low-calorie sweetener product in stevia.

Exogenous Nitric Oxide Reinforces Photosynthetic Efficiency, Osmolyte, Mineral Uptake, Antioxidant, Expression of Stress-Responsive Genes and Ameliorates the Effects of Salinity Stress in Wheat

Salinity stress is one of the major environmental constraints responsible for a reduction in agricultural productivity. This study investigated the effect of exogenously applied nitric oxide (NO) (50 μM and 100 μM) in protecting wheat plants from NaCl-induced oxidative damage by modulating protective mechanisms, including osmolyte accumulation and the antioxidant system. Exogenously sourced NO proved effective in ameliorating the deleterious effects of salinity on the growth parameters studied. NO was beneficial in improving the photosynthetic efficiency, stomatal conductance, and chlorophyll content in normal and NaCl-treated wheat plants. Moreover, NO-treated plants maintained a greater accumulation of proline and soluble sugars, leading to higher relative water content maintenance. Exogenous-sourced NO at both concentrations up-regulated the antioxidant system for averting the NaCl-mediated oxidative damage on membranes. The activity of antioxidant enzymes increased the protection of membrane structural and functional integrity and photosynthetic efficiency. NO application imparted a marked effect on uptake of key mineral elements such as nitrogen (N), potassium (K), and calcium (Ca) with a concomitant reduction in the deleterious ions such as Na⁺. Greater K and reduced Na uptake in NO-treated plants lead to a considerable decline in the Na/K ratio. Enhancing of salt tolerance by NO was concomitant with an obvious down-regulation in the relative expression of SOS1, NHX1, AQP, and OSM-34, while D2-protein was up-regulated.

Beneficial Features of Biochar and Arbuscular Mycorrhiza for Improving Spinach Plant Growth, Root Morphological Traits, Physiological Properties, and Soil Enzymatic Activities

Biochar and arbuscular mycorrhizal fungi (AMF) can promote plant growth, improve soil properties, and maintain microbial activity. The effects of biochar and AMF on plant growth, root morphological traits, physiological properties, and soil enzymatic activities were studied in spinach (Spinacia oleracea L.). A pot experiment was conducted to evaluate the effect of biochar and AMF on the growth of spinach. Four treatments, a T1 control (soil without biochar), T2 biochar alone, T3 AMF alone, and T4 biochar and AMF together, were arranged in a randomized complete block design with five replications. The biochar alone had a positive effect on the growth of spinach, root morphological traits, physiological properties, and soil enzymatic activities. It significantly increased the plant growth parameters, such as the shoot length, leaf number, leaf length, leaf width, shoot fresh weight, and shoot dry weight. The root morphological traits, plant physiological attributes, and soil enzymatic activities were significantly enhanced with the biochar alone compared with the control. However, the combination of biochar and AMF had a greater impact on the increase in plant growth, root morphological traits, physiological properties, and soil enzymatic activities compared with the other treatments. The results suggested that the combined biochar and AMF led to the highest levels of spinach plant growth, microbial biomass, and soil enzymatic activity.