ABSTRACT
Increases in abscisic acid (ABA) concentration might increase yields, and decrease in ABA sensitivity may improve drought tolerance. The hypothesis that the genetic difference in ABA sensitivity is associated with drought tolerance is substantiated by the findings of T. Oritani and R. Yoshida who observed that a soybean cultivar sensitive to ABA senesced several weeks earlier than another cultivar that was less sensitive. The higher drought tolerance of the transgenic plants is related to IAA involvement in plant adaptation, that is, in the hormone-induced modification of plant hormonal status and osmoregulation process. Both the experiments showed inhibition of ABA accumulation at low water potential is associated with severe inhibition of primary root elongation, compared to untreated or nonmutant seedlings. Inhibition of ethylene production increased spermine and the incorporation of methionine into polyamines. Incubation of diamines and polyamines with microsomal membranes markedly reduced the fluidity of the lipid bilayer.
