Photosystem II is extremely susceptible to environmental alterations, particularly high temperatures. The maintenance of an efficient photosynthetic system under stress conditions is one of the main issues for plants to attain their required energy. Nowadays, searching for stress alleviators is the main goal for maintaining photosynthetic system productivity and, thereby, crop yield under global climate change. Potassium silicate (K₂SiO₃, 1.5 mM) and silicon dioxide nanoparticles (SiO₂NPs, 1.66 mM) were used to mitigate the negative impacts of heat stress (45 °C, 5 h) on wheat (Triticum aestivum L.) cv. (Shandawelly) seedlings. The results showed that K₂SiO₃ and SiO₂NPs diminished leaf rolling symptoms and electrolyte leakage (EL) of heat-stressed wheat leaves. Furthermore, the maximum quantum yield of photosystem II (Fv/Fm) and the performance index (PI_abs), as well as the photosynthetic pigments and organic solutes including soluble sugars, sucrose, and proline accumulation, were increased in K₂SiO₃ and SiO₂NPs stressed leaves. At the molecular level, RT-PCR analysis showed that K₂SiO₃ and SiO₂NPs treatments stimulated the overexpression of PsbH, PsbB, and PsbD genes. Notably, this investigation indicated that K₂SiO₃ was more effective in improving wheat thermotolerance compared to SiO₂NPs. The application of K₂SiO₃ and SiO₂NPs may be one of the proposed approaches to improve crop growth and productivity to tolerate climatic change.

Global climate change is a significant challenge that will significantly lower crop yield and staple grain quality. The present investigation was conducted to assess the effects of the foliar application of either Si (1.5 mM) or Si nanoparticles (1.66 mM) on the yield and grain quality attributes of two wheat genotypes (Triticum aestivum L.), cv. Shandweel 1 and cv. Gemmeiza 9, planted at normal sowing date and late sowing date (heat stress). Si and Si nanoparticles markedly mitigated the observed decline in yield and reduced the heat stress intensity index value at late sowing dates, and improved yield quality via the decreased level of protein, particularly glutenin, as well as the lowered activity of α-amylase in wheat grains, which is considered a step in improving grain quality. Moreover, Si and nanoSi significantly increased the oil absorption capacity (OAC) of the flour of stressed wheat grains. In addition, both silicon and nanosilicon provoked an increase in cellulose, pectin, total phenols, flavonoid, oxalic acid, total antioxidant power, starch and soluble protein contents, as well as Ca and K levels, in heat-stressed wheat straw, concomitant with a decrease in lignin and phytic acid contents. In conclusion, the pronounced positive effects associated with improving yield quantity and quality were observed in stressed Si-treated wheat compared with Si nanoparticle-treated ones, particularly in cv. Gemmeiza 9.

To assess the effect of triacontanol (TRIA) on rice plants grown under normal or drought conditions, rice seeds were presoaked in TRIA (35 ppm) for two hours. After 20 days of sowing, rice seedlings developed from TRIA-treated or untreated seeds were subjected to drought stress. After 10 days of plant exposure to drought stress, data of major growth attributes and the content of photosynthetic pigments were recorded. Moreover, the effect of drought stress on stomatal conductance and the photochemical efficiency of PSII (Fv/Fm) were followed. The data obtained indicated that the species of rice (Oryza sativa L.) cultivar Giza 177 under investigation was sensitive to drought stress where there were significant decreases in the fresh and dry weights of shoots and roots and in stomatal conductance, as well as in the content of chlorophyll a, chlorophyll b, and carotenoids. Seed priming with TRIA enhanced both growth and acquired plant tolerance to drought stress. Thus, TRIA via the enhancement of stomatal conductance through the regulation of stomatal closure, the rate of water loss, ABA metabolism, the accumulation of osmolytes, and the regulation of aquaporins genes improved the water status of plants grown under water scarcity. Moreover, TRIA via increasing the content of free amino acids and sugars under drought stress may increase the chance of plant tissues to retain more water under scarcity conditions.

A field trial study was conducted for two consecutive seasons 2020 and 2021 in approximately 8-month-old jojoba plants to evaluate the physiological responses following salt treatment and the role of proline as a foliar application to enhance jojoba tolerance to salinity stress. Jojoba plants were irrigated once a week for four months with diluted seawater in concentrations of 5000, 10,000, and 15,000 ppm and tap water (control). Anti-stress proline was applied four times throughout the experiment, the first at the beginning of the experiment and another three times at 30-day intervals, at concentrations of 0, 300, and 450 ppm. The effect of proline treatments on jojoba plant behavior includes growth vegetative characteristics, namely plant height increase percentage (PHIP), shoot number increase percentage (NSIP), stem diameter increase percentage (SDIP), number of leaves, leaf thickness, leaf area, and fresh and dry weights of leaves, and chemical characteristics, namely chlorophyll a and b, total chlorophyll, carotenoids, leaf mineral contents (N, P, K, Na, and Cl), total phenolic content (TPC), and proline concentration. Moreover, the impacts of proline on hydrogen peroxide (H₂O₂), superoxide anion (O₂^•−), malondialdehyde (MDA), and ion leakage (IL) under salinity stress were investigated. Briefly, proline at 450 ppm enhanced all studied growth and physiological characteristics and promoted the antioxidant system of jojoba plants compared with the control and other treatments. The anatomical structure of leaves was also examined, and favorable variations in the anatomical structure were detected in the stressed and proline-treated plants. Exogenous application of proline enhanced most of this anatomical characteristic of jojoba leaf under saline stress. In conclusion, proline as a foliar application at 450 ppm under salinity stress of 10,000 ppm enhances jojoba tolerance to salinity stress by modifying the physicochemical and morphological characteristics of jojoba plants.

Background: Esculin, a natural coumarin glucoside with antioxidant properties, is a secondary metabolite found in various plant species and has been traditionally valued for its medicinal benefits. This study focused on evaluating the ability of esculin to enhance flax plant tolerance to lead (Pb) toxicity. Methodology: Flax plants were irrigated with either distilled water or a lead solution (200 mg/L) and subsequently treated with foliar sprays of esculin at concentrations of 0, 50, and 100 mg/L. Results: The findings revealed that esculin application significantly improved the plants’ resilience to Pb toxicity. It reduced the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and electrolyte leakage (EL), while improving the membrane stability index (MSI). Esculin effectively alleviated oxidative stress by boosting the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), phenylalanine ammonia-lyase (PAL), and tyrosine ammonia-lyase (TAL), in addition to increasing total phenols and proline content. Furthermore, esculin contributes to maintaining membrane integrity by reducing sodium (Na) uptake and increasing the absorption of potassium (K), magnesium (Mg), phosphorus (P), and calcium (Ca). It also minimizes Pb accumulation in the plants, further mitigating lead toxicity. These effects were associated with improved photosynthetic pigment concentrations, higher levels of soluble sugars (TSS), and an increase in free amino acids (FAA) under lead stress conditions. The application of esculin enhanced key agronomic traits, including shoot and root growth, fresh and dry biomass, seed yield per plant, and 1000-seed weight. Additionally, seed quality improved, with increased oil, carbohydrate, and protein content under Pb stress conditions. Conclusion: In summary, esculin glycosides is a novel approach that effectively reduces lead toxicity and enhances stress tolerance in flax, offering a promising strategy for managing heavy metal stress in crops.