Effect of methanol spraying on some morphophysiological characteristics, yield and yield components of sunflower (Helianthus annuus L.) under drought stress conditions

Sunflower (Helianthus annus L.) is one of the five important oil plants of Iran. Water deficit stress is one of the most important limiting factors in sunflower cultivation. Methanol is used to deal with environmental stresses, especially dehydration. Preventing or reducing light respiration, delaying leaf senescence, increasing photosynthetic activation period and leaf area duration index and increasing Co2 fixation are among the roles of methanol application in plants. Therefore, this study was conducted to investigate the effect of methanol spraying on some morphophysiological characteristics, yield and yield components of sunflower under drought stress conditions.

This field experiment was conducted as a split plot based on randomized complete block design with three replications in Birjand, Iran, in 2017. The main plots included two levels irrigation (irrigation after 80 and 160 mm evaporation form class A pan). On the other hand, the sub- plots included five levels of methanol spraying; control (no spraying), 7, 14 and 21 v/v. Statistical analysis was performed using MSTATC software. Duncan's multiple range test at the 5% level of probability was used to compare the means.ResultsResults showed that deficit irrigation reduced stem diameter, number of seeds per head and kernel / husk weight ratio. Methanol spraying also increased the number of seeds per head. Also, methanol spraying improved most of the studied traits under two irrigation treatments. So that under drought stress conditions, foliar application with 28% volumetric methanol increased plant height (9.9%), stem diameter (5%) and leaf number per plant (14.7%). Compared to control, foliar application with 14% volumetric methanol increased chlorophyll content (8%) and foliar application with 21% volume methanol increased stomatal conductance (34.7%), 1000-grain weight (12%), grain yield (27.9%) and biological yield (23.4%). According to the results, under optimum irrigation conditions, maximum sunflower grain yield was obtained with 28% volumetric methanol spraying, but under drought stress conditions, spraying with 21% volume methanol was the best one.

The results showed that foliar application of methanol under optimum and also deficit irrigation conditions did not affect the percentage and yield of sunflower oil seed, but increased seed yield. Maximum grain yield under optimum irrigation was obtained with 28% volumetric spraying, which was 27% more than control. Also, the results showed that under arid and semi-arid conditions of Birjand, deficit irrigation with using methanol (21% volumetric) produces acceptable grain yield.Chlorophyll meter, Leaf temperature, Oil percentage, Stomatal conductance