Chitosan and its components have beneficial effects on a wide variety of plant species. Yet, their effects on wheat plants under drought stress are not well known. So, a field experiment was laid out in order to evaluate the effect of chitosan nanoparticles (NPs) on wheat. The wheat seeds were sown in plots. Then, the chitosan NPs were added to them through soil and foliar application at tillering, stem elongation, and heading stages. Results indicated that the drought stress significantly decreased majority of the studied traits compared to the normal irrigation. Application of the NPs especially 90 ppm increased leaf area (LA), relative water content (RWC), chlorophyll content, photosynthesis rate, catalase (CAT), and superoxide dismutase (SOD) activities, yield, and biomass compared to the control. Finally, our results highlight that usage of the chitosan NPs especially 90 ppm can mitigate adverse effects of drought in the wheat under drought stress.

Phytohormones salicylic acid and strigolactones play critical roles in mediating plant responses to environmental stress including drought stress. This study investigated whether foliar application of salicylic acid and strigolactones in the form of GR24 will improve the drought tolerance of winter wheat (T-riticum aestivum L.) plants. Exogenous application of strigolactone and salicylic acid increased proline and soluble sugar content as well as stomatal conductance, photosynthesis and transpiration rate of wheat plants. Higher amounts of all above mentioned characteristics are indicative of the higher drought tolerance of hormone-treated plants. In this experiment, application of hormones decreased the drought-induced rise in the content of H₂O₂ a factor known to lead to membrane lipid peroxidation, toxicity, and cell death. Hormones external application dampened leaf water potential that contributes to plant-level physiological drought tolerance. Drought tolerance features magnified when we used both hormones together. Our finding suggests that hormonal application can improve osmotic adjustment and decrease adverse effects of drought stress on wheat plants.

As a step towards the profitable employment of nanoparticles (NPs) in agriculture, effects of chitosan NPs was probed on barley plants under late season drought stress. A factorial experiment was performed based on a randomized complete block design with three replications. The experimental factors included the chitosan NPs concentrations (0 (control), 30, 60 and 90 ppm), application methods (foliar and soil application) and irrigation regimes (well-watered and withholding of irrigation for 15 days after pollination). The barley seeds were separately planted in pots. Then, the NPs were added to them through the soil and foliar application at three stages. The results indicated that using the chitosan NPs, especially 60 and 90 ppm, significantly increased the leaf area (LA), the leaf color (SPAD), the number of grain per spike, the grain yield and the harvest index compared to the control. Also, drought stress significantly decreased the yield and yield components compared to the well-watered plants. In contrast, using the chitosan NPs in plants under drought stress significantly increased the relative water content (RWC), the 1000-grain weight, the grain protein, the proline content, the catalase (CAT) and the superoxide dismutase (SOD) compared to the control. There was no a significant difference between two methods of using NPs in most studied traits. The results highlighted that using the chitosan NPs, especially 60 and 90 ppm, in both irrigation regimes can significantly improve the majority of the studied traits compared to the control and mitigate the harmful effects of drought stress.

Strigolactones (SLs) have been implicated in many plant biological and physiological processes, including the responses to abiotic stresses such as drought, in concert with other phytohormones. While it is now clear that exogenous SLs may help plants to survive in harsh environmental condition, the best, most effective protocols for treatment have not been defined yet, and the mechanisms of action are far from being fully understood. In the set of experiments reported here, we contrasted two application methods for treatment with a synthetic analog of SL, GR24. A number of morphometric, physiological and biochemical parameters were measured following foliar application of GR24 or application in the residual irrigation water in winter wheat plants under irrigated and drought stress conditions. Depending on the concentration and the method of GR24 application, differentiated photosynthesis and transpiration rate, stomatal conductance, leaf water potential, antioxidant enzyme activities and yield in drought conditions were observed. We present evidence that different methods of GR24 application led to increased photosynthesis and yield under stress by a combination of drought tolerance and escape factors, which should be considered for future research exploring the potential of this new family of bioactive molecules for practical applications.