Effects of methanol spraying on some biochemical and physiological characteristics of soybean (Glycine max L.) under drought stress

In order to investigate the effect of foliar application of methanol and drought stress on some biochemical properties of soybean (Glaycine max L.), a pot experiment was done in farm environment. The experiments were done in factorial form based on a completely random design with 3 repetitions. Treatments included three irrigation levels of normal (irrigation after 40% depletion of available soil moisture), average stress (irrigation after 60% depletion of available soil moisture), and severe stress (irrigation after 70% depletion of available soil moisture) as the main factor and levels of methanol in the form of foliar application including control solutions (foliar application without use of methanol) and solutions of 14.7% and 21% of methanol as secondary factor. Results obtained from the study showed that there were significant differences between various levels of methanol in content of chlorophyll and carotenoid compounds, relative water content, phenolic compounds, total protein content, proline, and leaf peroxide hydrogen in (P≤0.01). With the application of stress from mild to severe, application of 14% methanol showed more pronounced effects on total chlorophyll content, chlorophyll a and chlorophyll b. Moreover, under mild and severe stress conditions, with application of the highest value of methanol, production of peroxide hydrogen reached lowest level and the content of phenolic compounds increased with the increased application of methanol from 7% to 14%. According to the obtained results, with application of 14% methanol, more increase was observed in the efficiency of proline under severe stress conditions. Increasing the volume of methanol from 7 to 14%, the relative water content was preserved under stress conditions. For protein, with increased drought stress, the effect of application of 14% methanol was the same in comparison with 21% methanol. Therefore, according to the obtained results, it is concluded that methanol could improve plant resistance against drought stress.