ABSTRACT
The aim of this study was to contrast the effects of drought stress on polyamine oxidases gene expression andactivity as well as photosynthetic efficiency in relatively tolerant (Karoon) and sensitive (260) maize genotype.d Reduction in leaf relative water content as a result of drought led to increase in root growth, butdiminished shoot growth indices. Under drought stress, activity of antioxidant enzyme, catalase, significantlyincreased in both genotypes, whereas significant higher activity of superoxide dismutase and peroxidase wasonly observed in Karoon genotype. Expression of polyamine oxidase (PAO) genes (zmPAO1, zmPAO2,zmPAO3, zmPAO4, zmPAO5, zmPAO6) and activity of enzymatic polyamine oxidation was increased in bothgenotypes under drought stress. The enhancement in PAO gene expression and enzyme activity was moreprominent in Karoon cultivar compared to 260. Chlorophyll a fluorescence and fast induction kinetics werenegatively influenced by drought stress. These parameters were more affected in 260 cultivar compared withKaroon. Our results suggest that under drought stress, higher activity of polyamine oxidase pathway in backconversion of Spermine and spermidine to putrescine (protectant of photosynthetic apparatus) as well as higherantioxidant enzymes activity in Karoon cultivar, may play a role in higher efficiency of photosynthetic processin this cultivar