Genetic variability of oxalate oxidase activity and elongation in water-stressed primary roots of diverse maize and rice lines.

A previous study of maize primary roots under water stress showed pronounced increases in oxalate oxidase activity and apoplastic hydrogen peroxide in the apical region of the growth zone where cell elongation is maintained. We examined whether increased oxalate oxidase activity in water-stressed roots is conserved across diverse lines of maize and rice. The maize lines exhibited varied patterns of activity, with some lines lacking activity in the apical region. Moreover, none of the rice lines showed activity in the apical region. Also, although the genotypic response of root elongation to water stress was variable in both maize and rice, this was not correlated with the pattern of oxalate oxidase activity. Implications of these findings for root growth regulation under water stress are discussed.