The effect of plant growth regulator treatments on the levels of ethylene emanating from excised turgid and wilted wheat leaves.

Abscisic acid (ABA) inhibits the production of ethylene induced by water stress in excised wheat leaves and counteracts the stimulatory effect of 6-benzyladenine (BA) on this process. The stimulatory effect of BA and the inhibitory effect of ABA were equally pronounced whether external or endogenous ethylene levels were determined. When leaves were sprayed or floated on solutions of BA, indole-3-acetic acid (IAA), gibberellic acid (GA3), or ABA, the relative activities of these growth regulators on stress-induced ethylene at 10(-4) mol l(-1) were BA>IAA >GA3>controls>ABA. In non-stressed leaves, however, where the levels of ethylene produced were 2-20 times smaller, the relative activities were IAA >BA>GA3>controls>ABA. The effects of BA and ABA spray treatment on water stress induced ethylene were closely similar whether the solutions were applied 2 or 18 h prior to the initiation of water stress. The relationships between the levels of endogenous growth regulators in the plant and ethylene release induced by water stress are discussed.