EFFECTS OF BENZYLADENINE AND GIBBERELLIC ACID ON THE RESPONSES OF TOMATO PLANTS TO ANAEROBIC ROOT ENVIRONMENTS AND TO ETHYLENE

Abstract

S ummary Benzyladenine (BA) and gibberellic acid (GA) were applied together as a foliar spray to young tomato plants growing in pots of well drained soil, waterlogged soil or in nutrient solution supplied with air (aerobic), nitrogen gas (anaerobic), or ethylene (20 or 100 ul 1 −1 in air) for up to 6 days. BA and GA (10 fig ml −1 ) lessened the inhibitory effects of waterlogging on stem elongation, transpiration and the increase of fresh and dry wt of the shoots. In absolute terms the promotion of shoot growth by BA and GA was greater in plants growing in non‐waterlogged than in waterlogged soil. Root growth was inhibited by BA and GA. The effect of waterlogging in promoting adventitious rooting at the base of the stem was reduced by BA and GA. Epinastic curvature by petioles was promoted by growing plants in waterlogged soil or anaerobic solution culture in association with an increase in the production of ethylene by the petioles. Applications of BA and of GA inhibited this epinastic growth but they did not lower the rate of ethylene production. However BA and GA diminished the effectiveness of ethylene as a stimulator of epinastic curvature. The application of ethylene to the roots inhibited the accumulation of dry wt by the root system and decreased slightly the growth promoting effects of BA and GA in the shoots. The inhibiting effect of waterlogging the root system on stem elongation could be offset if adventitious roots maintained in well aerated conditions were previously induced on the main stem above the primary roots. Epinastic curvature and ethylene production were not decreased by the presence of an adventitious root system. The extent to which applications of BA and GA may reflect the activity of endogenous hormones produced by aerobic roots is discussed.