Effect of Salicylic Acid Foliar Application on Physiological Indices and Induction of Terminal Heat Stress Tolerance of Quinoa in Ahvaz

IntroductionQuinoa (Chenopodium quinoa L.) is a dicotyledonous, allotetraploid, three-carbon, annual, optional salt-loving plant and is native to South America and the Andean highlands. The growth period of the plant varies between 70 and 240 days depending on the cultivated area. The main product of this plant is the seed, which has a high nutritional value in terms of protein, amino acid balance, unsaturated fat, vitamins, and minerals. Like other plants, quinoa faces various environmental stresses during its growth period, and its growth and yield are a function of environmental factors and their mutual effects. The occurrence of high temperatures during the sensitive stages of plant growth, such as flowering and seed formation, may cause a significant decrease in quinoa yield, and high temperature has been cited as one of the most important challenges for the cultivation and expansion of quinoa in the world. Salicylic acid acts as a signal molecule and plays an important role in regulating growth and development processes in plants under environmental stress. Salicylic acid increases the content of relative humidity, accumulation of dry matter, and the amount of chlorophyll.Materials and MethodsThe objective of this research is to assess the physiological responses of quinoa cultivars to varying planting dates and the impact of foliar application of salicylic acid in mitigating the adverse effects of end-of-season heat stress during the 2021-2022 crop year. The study was conducted at the research farm of the Faculty of Agriculture, Shahid Chamran University of Ahvaz, using a split-split plot design within a randomized complete block framework, with three replications. In this experiment, three factors a) planting date including October 12, November 11, and December 11, and b) foliar application of salicylic acid in the two stages of budding and the beginning of flowering including non-application, 1.5 mM and 3 mM and c) Quinoa cultivars including Titicaca, Giza, Q12 and Redcarin were investigated.Results and DiscussionThe effect of investigated factors such as planting date, salicylic acid, and variety on different traits had statistically significant differences. The results showed that the maximum amount of stomatal conductance and the relative content of leaf water belonged to the date of October 12. The highest biological yield and seed yield were observed under conditions of application of 1.5 and 3 mM salicylic acid, respectively. Probably, salicylic acid has increased the growth and accumulation of dry matter by improving carbon fixation, synthesis of metabolites, and maintaining the water status of plant tissues. Based on the results of the comparison of the mean of the three-way interaction, the maximum amount of biological yield and seed as the most important goals of quinoa plant cultivation, respectively, in the treatment of not using salicylic acid in the Redcarin cultivar on the planting date of December 11 and the application of 3 mM salicylic acid was obtained in the variety Redcarin on the planting date of October 12. The highest rate of net assimilation and the growth rate of the product belonged to the treatments of no application of salicylic acid in the Redcarin cultivar on December 11 and no application of salicylic acid in the Giza cultivar on October 12, respectively. The treatment of not using salicylic acid in the Redcarin variety on the planting date of October 12 was also able to achieve a high harvest index.Conclusion According to the obtained results, it seems that to achieve a high seed yield of quinoa, it is possible to benefit from the treatment of 3 mM salicylic acid in the Redcarin variety on the planting date of October 12.