Althought safflower is a tolerant crop against many environmental stresses, but its yield and performance reduce under stress. The aim of this experiment was to investigate the effect of silicon (Si) application on the possibility of increasing salinity resistance and related mechanisms in safflower. A greenhouse experiment was conducted to investigate the effects of Si spraying (0, 1.5 and 2.5 mM) on safflower plants grown under salt stress condition (non-saline and 10 dS m⁻¹). Salinity reduced seedling emergence percent and rate, growth parameters and disrupted ion uptake but increased emergence time and specifc leaf weight. Spraying of Si increased plant height, fresh and dry weight, leaf area, relative water content (RWC), potassium, calcium and silicon content, while sodium absorption was decreased. As a result, the K⁺/Na⁺ and Ca²⁺/Na⁺ ratios were increased. Elevated ion contents and ratios indicate an enhanced selectivity of ion uptake following silicon application and may increase ion discrimination against Na⁺. Treatment with 2.5 mM Si showed the most positive effect on the measured growth traits. Decrement in leaf area ratio under salinity indicates a more severe effect of salinity on leaf area compared to biomass production. On the other hand, silicon reduced the specific leaf weight under stress and non-stress conditions, which revalues the positive effects of silicon on leaf area expansion. Improvement of RWC may a reason for the icrease in leaf area and biomass production. Data shows that spraying with Si especialy with 2.5 mM can reduce salinity stress damage to safflower and increase biomass production.

To investigate how and in what amounts biochar and methyl jasmonate can improve drought tolerance of barley. A two-year experimental study was conducted in a factorial randomized complete block design (n = 5) in the research greenhouse of Zanjan University, Iran, to investigate the possible effects of biochar and methyl jasmonate on some traits of winter barley under drought conditions. Two irrigation regimes, D₀ (full irrigation in soil field capacity as control) and D₁ (withholding irrigation immediately after flowering stage), three methyl jasmonate spray densities [0 (M₀), 50 (M₅₀), and 100 (M₁₀₀) μM] and four levels of biochar in soil [0% (B₀), 0.25% (B_0.25), 0.5% (B_0.5), 1% (B₁) per soil weight] were used in this experiment. In this study, drought reduced two-year average leaf area (LA) by 96%, stomatal conductance (gs) by 84%, and photosynthetic water use efficiency (PWUE) by 64%. In addition, drought reduced chlorophyll-b by 1.5% and 81% and transpiration rate (Tr) by 2.5% and 78% in the first and second years, respectively. However, the application of biochar and methyl jasmonate improved all the traits studied in both D0 and D1 drought-treated plants. For most of the parameters studied, the optimal combination of biochar and methyl jasmonate that optimized water use efficiency and alleviated drought was 0.25% and 50 μM, respectively. The synergistic action of biochar and jasmonates improved the tolerance of barley to water stress.

Biochar improves soil physical, biochemical, and microbial properties, leading to the amelioration of soil fertility, which, in turn, results in better growth and yield in crop plants. The current study aimed to evaluate whether using different levels of biochar can enhance soil characteristics and plant attributes. Accordingly, an experimental study was conducted in 2022 using a randomized complete block design with four replications (n = 4) in the experimental glasshouse of the University of Zanjan, in which two regimes of irrigation (D0, full irrigation as the control; D1, water scarcity was applied immediately after the flowering stage for two weeks) and four levels of natural mineral biochar (0% as the control treatment, 0.25, 0.5, and 1% of soil weight) were applied. The results indicated that drought substantially decreased the organic carbon content of the soil and the grain yield while increasing the available phosphorous, soil carbohydrate content, and microbial biomass of the soil. Biochar could considerably alter the means of the studied soil quality parameters and the barley grain yield. Adding biochar could be considered a valid strategy to increase the resistance of plants to drought.

Soil and water salinization is a global treat for crop production and food security. Apply of phytohormones and nutrient management is a novel approach to reduce the negative impact of salinity. Hence the effects of salicylic acid (0, 600, 1200, and 1800 µM) and silicon (0, 1.5, and 2.5 mM) foliar application on safflower (Carthamus tinctorius L.) seed yield and quality were investigated under salt stress conditions (1.7, 7.5, and 15 dS m^− 1). Salinity decreased capitulum number, seed number per capitulum, 100-seed weight, seed yield, oil percentage, oil yield, linoleic acid content, palmitic and linoleic acids yield, and seed potassium content. Application of salicylic acid (SA) and silicon (Si) increased biological and seed yield, oil content, oil yield, linoleic acid content, palmitic and linoleic acid yield but decreased stearic and oleic acid content and oleic acid yield. The harvest index (HI) was decreased with increasing salinity levels, indicating a stronger effect of salinity on seed yield more than biomass production. In contrast, SA and Si, whether alone or together, increased HI. The appropriate concentration of SA in saline and non-saline conditions was 1200 µM, but Si was different in salinity levels. Under non-stress and moderate stress conditions 2.5 mM Si showed better performance, while at severe salinity level, 1.5 mM Si showed an appropriate state. Oil content and quality improved by increasing linoleic acid and reducing stearic and palmitic acids by application of SA and Si. The content of seed elements with the application of salt, SA and Si showed different trends. Nitrogen content increased under salt stress, but potassium content decreased and sodium content did not change under saline and non-saline conditions. The application of SA and Si increased nitrogen and potassium content in stressed and non-stressed conditions, but had no significant effect on the amount of sodium.