Abscisic acid and the after-effect of stress in tobacco plants.

Tobacco plants (Nicotiana rustica L.) were exposed to a period of stress of either mineral deprivation or salination of the root medium. Thereafter the plants were transferred back to the pre-stress growth medium, for study of the pattern of recovery. Abscisic acid (ABA) content and the extent of stomatal opening in leaves of tobacco plants were found to be inversely related. The results support the possibility that the phenomenon know as "after-effect of stress" may not be exclusive to recovery from water stress, but may be typical of the pattern of plant recovery from the effects of several growth restricting environments. It is suggested that the after-affect results from the delay in resumption of the pre-stress hormonal balance in the plant, particularly with regard to ABA, after termination of the stress.