Protein differences between fruits of rin, a non-ripening tomato mutant, and a normal variety.

Fruit extracts of non-ripening tomato Lycopersicon esculentum Mill strain rin contain extra protein band comparing with the normal ripening cultivar Rutgers. Another band exists in both varieties, but disappears in Rutgers at the onset of ripening. The existence of a proteinaceous ripening inhibitor is suggested.

Water Permeability during Tomato Fruit Development in Normal and rin Nonripening Mutant.

This work tested one aspect of the relations between membrane permeability and fruit ripening. Membrane permeability was measured as [(3)H]water efflux rate from preloaded fruit pericarp disks. Different stages of fruit development were compared between two tomato (Lycopersicon esculentum Mill) strains: the normal Rutgers and the isogenic nonripening rin strain. The first significant increase in permeability was measured in Rutgers tissue at 110% of development, after fruit ripening had already begun as indicated by ethylene and CO(2) evolution and lycopene synthesis. The rin did not show any increase in tissue permeability during fruit development or maturation.Our results do not support the idea that the first event of the ripening process is an increase in membrane permeability. Nevertheless, the nonripening mutant fails to show the normal increase in permeability.

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.

Ethylene production and respiration in aging leaf segments and in disks of fruit tissue of normal and mutant tomatoes.

Leaf segments of tomato plants (Lycopersicon esculentum Mill.) of a normal strain and of two nonripening mutants rin and nor were aged in darkness. Respiration in leaf segments of all strains followed a climacteric-like pattern which was accompanied by a similar pattern of ethylene production. l-Methionine-U-(14)C vacuum-infiltrated into leaf segments at the beginning of the climacteric-like rise in respiration was metabolized to ethylene and CO(2) during the subsequent 48 hours to about the same extent in all strains. Pericarp disks of immature fruits of all strains also metabolized l-methionine-U-(14)C to ethylene and CO(2) to about the same extent during the first 48 hours following cutting and vacuum infiltration. Conversion of methionine to ethylene in disks was much more efficient than in aging leaf segments. The apparent capacity for increased production of ethylene in aging leaf segments and in response to wounding in pericap disks of rin and nor is contrasted with the absence of a respiratory climacteric and an associated large increase in ethylene production during natural aging of intact fruits of these two strains.

Transplantation Studies with Immature Fruit of Normal, and rin and nor Mutant Tomatoes.

The aim of the work reported herein was to determine whether the lack of normal ripening in fruits of rin and nor tomato mutants is due to the presence of ripening inhibitors or to the lack of ripening factors in the fruit. A fruit tissue transplantation technique was developed for this purpose.Disks of pericarp tissue were transplanted reciprocally between tomato fruits (Lycopersicon esculentum Mill.) of the rin and nor mutants and fruits of ;Rutgers,' a normally ripening cultivar. CO(2) and ethylene evolution rates were measured daily. To test whether materials are translocated between receptor fruits and transplanted disks, fruits were vacuum-infiltrated with (14)C-labeled amino acids and implanted with disks from unlabeled fruits.Normal ripening was not induced in disks of rin and nor tissues implanted in Rutgers fruit although development of yellow or yellow-orange colors associated with senescence of the mutant fruits was accelerated. Disks of Rutgers fruit tissue implanted in fruits of rin and nor ripened normally and concomitant with the intact Rutgers control fruits. The transplanted disks contained 28.8% as much label as found in disks of receptor fruits; thus, significant translocation into the implanted disks occurred. It is concluded that fruits of the mutants do not contain translocatable ripening inhibitors or lack translocatable ripening factors.

Comparison of Propylene-induced Responses of Immature Fruit of Normal and rin Mutant Tomatoes.

Continuous application of propylene to 40 to 80% mature fruits of normal tomato strains (Lycopersicon esculentum Mill.) advanced ripening in fruits of all ages by at least 50%. Although preclimacteric respiration was stimulated by propylene treatment, there was no concomitant increase in ethylene production. Once ripening commenced, the rates of endogenous ethylene production were similar in both propylene-treated and untreated fruits. Continuous exposure to propylene also stimulated respiration in immature fruits of rin, a nonripening mutant. Although respiration reached rates similar to those during the climacteric of comparable normal fruits there was no change in endogenous ethylene production which remained at a low level. Internal ethylene concentrations in attached 45 to 75% mature fruits of rin and a normal strain were similar. It is suggested that the onset of ripening in normal tomato fruit is not controlled by endogenous ethylene, although increased ethylene production is probably an integral part of the ripening processes.

Gibberellin delays ripening of tomatoes.

Treatment with gibberellic acid, at concentrations as low as 10(-7)M, of intact tomato fruits, or of pieces in tissue culture, markedly retarded ripening in terms of development of redness. Ethylene stimulations of color development were prevented by treatment with gibberellic acid, but ethylene stimulations of respiration were not. Gibberellin can delay the progress of some components of the ripening of fruit, preventing some of the changes triggered by ethylene.