The effect of gibberellin hormone on yield, growth indices, and biochemical traits of corn (Zea Mays L.) under drought stress

In order to investigate the effect of gibberellin hormone and drought stress on corn, an experiment was conducted as split plots based on a randomized complete block design with three replications. Treatments included moisture stress at three levels of normal irrigation (I0=60), medium stress (I1=90), and severe stress (I2=120) mm evaporation from class A evaporation pan as main factor and a sub factor of gibberellin hormone spraying at four levels non-consumption (G0=0), (G1=15ppm), (G2=20ppm), and (G3=25ppm). Results showed that the highest and lowest grain yields were observed in 60 mm evaporation from evaporation pan with 20 ppm gibberellin acid and 120 mm evaporation from the evaporation pan without using gibberellin acid as 9658.2 and 5797.3 kg/h, respectively. Also, under all levels of drought stress, gibberellin acid application increased grain yield of corn. The interaction of hormones and irrigation had a significant effect on starch, proline, alpha amylase, beta amylase, and protease. Drought stress increased proline concentration in corn leaf. Gibberellin hormone had no significant effect on proline concentration in corn leaf under drought stress conditions, but under prolonged drought stress, proline concentration increased. The application of 20 and 25 ppm gibberellin under moderate dehydration (90 mm evaporation from evaporation pan) increased leaf proline concentrations by 36% and 50%, respectively, compared with control treatment (no gibberellin consumption). Under severe drought stress conditions (120 mm evaporation from the evaporation pan), proline concentrations with 20 and 25 ppm gibberellin were 32% and 21% higher than gibberellin consumption, respectively. Overall, the results showed that gibberellin acid, through positive effects on increasing and improving the yield components, can ultimately increase corn grain yield.