Melatonin application enhances biochar efficiency for drought tolerance in maize varieties: Modifications in physio-biochemical machinery

The roles of biochar, melatonin (Me), and P application have been well researched; however, biochar with Me application in helping plants be more drought tolerant are little understood. The aim of this greenhouse study is to evaluate the effects of Me and P in combination with biochar made from date (Phoenix dactylifera L.) and wheat (Triticum aestivum L.) residues on vegetative growth and biochemical impact of maize (Zea mays L.) varieties Azam and Mallika under drought stress. Date residue and wheat straw biochars combined with melatonin (D+W+Me) reduced oxidative stress caused by excessive reactive oxygen species (ROS) the most. Generations of ROS species (malondialdehyde [MDA], H2O2, thiobarbituric acid reactive substances [TBARS], O-2(-), lipoxygenase [LOX], and electolyte leakage [EL]) was 118 and 700% higher in Azam variety compared to Mallika. The application of D+W+Me maintained osmolyte accumulation, alpha -amylase activity, and antioxidant enzyme activities at higher levels in Mallika (2-7, 29, 9-55%, respectively) than in Azam and the rest of the treatments. The D+W+Me treatment also enhanced leaf gas exchange traits in Mallika (3-20%) under drought stress, helping to main better photosynthesis machinery. The D+W+P and D+Me treatments application alleviated a portion of the drought stress. Overall, Me application with date residue and wheat straw biochars enhanced the efficiency of biochar, by better assuaging the adverse drought stress influences.