Arbuscular Mycorrhizal Fungi Inoculation Mediated Changes in Phytohormones Under Drought Stress

Changes in climatic conditions around the world have increased day by day which leads to droughts in agricultural lands. Nowadays various technologies and methodologies are being used to protect plants from drought stress. Among various methods, arbuscular mycorrhizal fungi (AMF) mediated alleviation of drought stress was found to be a more efficient one. Most of the AMF studies revealed their importance for water status, gas exchange, and nutrient uptake, but they also act as potential candidates for the regulation of phytohormones. At present, there is no comprehensive and quantitative evaluation of the phytohormonal changes under drought stress. Therefore, we carried out a random-effects model of meta-analysis to explore the influences of AMF inoculation on phytohormones under drought stress. Results showed that stress hormones increased by 2% but were non-significant, whereas growth hormones significantly increased by 24% in AMF-inoculated plants. Among phytohormones, indole acetic acid (IAA) content increased significantly by 37%. Also increased content of jasmonic acid (JA) (25%), salicylic acid (SA) (25%), gibberellins (24%), and brassinosteroids (11%) compared to non-mycorrhizal plants. Due to low sample size, we treated results with caution. However, abscisic acid (ABA) contents decreased by 6% in AMF-inoculated plants. Among growth hormones, IAA showed more positive effect sizes in AMF-inoculated plants under drought stress conditions. Among phytohormones, JA and SA had a positive effect size, whereas ABA showed a negative effect size. These results conclude that depending upon the level of stress, AMF species and plant species determined the accumulation of phytohormones under drought stress.