STOMATAL RESPONSES OF VICIA-FABA L TO INDOLE ACETIC-ACID AND ABSCISIC-ACID

Evidence is presented that stomata in isolated epidermal peels of Vicia faba L. open in darkness in response to the external presence of indole acetic acid (IAA) in the incubation medium. The effect of IAA is found to be overcome completely in the presence of either TRIS or MES buffers. In the absence of buffer, II. faba stomata are shown to be influenced by IAA in a concentration-dependent trend which reached a maximum at an [IAA] of 10(-3) mol m(-3). Further investigations reveal that stomata in this species can be shown to respond to the presence of IAA and another phytohormone, abscisic acid (ABA). IAA and ABA are demonstrated to be antagonistic in their effects provided the incubation conditions are suitable. The data are discussed in relation to stomatal responses of other species in different treatment conditions. Recommendations are made with respect to standardization of incubation media during epidermal peel experiments.