Effects of Abscisic Acid and Benzyladenine on Fruits of Normal and rin Mutant Tomatoes

Since ethylene application did not induce ripening in detached fruits of the nonripening mutant rin we initiated studies to determine possible involvement of other hormones. We proposed that the lack of ripening in mutant rin tomato fruit may result from a lack of abscisic acid or from excessive endogenous levels of cytokiuin. Application of abscisic acid (3 x 10(-5)m and 10(-3)m) to detached fruits of a normal strain (Lycopersicon esculentum Mill. cv. ;Rutgers') reduced the time to initiate ripening by about 50%. This acceleration of the onset of ripening appeared not to be due to an increased rate of ethylene production. Abscisic acid did not alter respiration or ethylene production or induce ripening in rin fruit. Ripening in Rutgers fruit was not influenced by treatment with 6-benzyladenine (4.44 x 10(-6)m, 4.44 x 10(-5)m or 1.8 x 10(-4)m). Fruits of the mutant rin showed no response to exogenous BA. However, senescence rates of leaf disks of both Rutgers and rin were significantly inhibited by as little as 10(-7)m exogenous benzyladenine. The results are discussed in relation to previous studies of the physiology of rin fruits and it is concluded that endogenous levels of ABA and cytokinins do not account for the lack of ripening in rin fruit.