A simple and sensitive chemical assay was developed for 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene. The assay is based on the liberation of ethylene from ACC at pH 11.5 in the presence of pyridoxal phosphate, MnCl2 and H2O2. This assay was used to detect ACC in extracts of tomato fruits (Lycopersicon esculentum Mill.) and to measure the activity of a soluble enzyme from tomato fruit that converted S-adenosylmethionine (SAM) to ACC. The enzyme had a Km of 13 μM for SAM, and conversion of SAM to ACC was competitively and reversibly inhibited by aminoethoxyvinylglycine (AVG), an analog of rhizobitoxine. The Ki value for AVG was 0.2 μM. The level of the ACC-forming enzyme activity was positively correlated with the content of ACC and the rate of ethylene formation in wild-type tomatoes of different developmental stages. Mature fruits of the rin (non-ripening) mutant of tomato, which only produce low levels of ethylene, contained much lower levels of ACC and of the ACC-forming enzyme activity than wild-type tomato fruits of comparable age.
Little or no change in ethylene or C02 production occurred in rin tomato mutant fruits monitored for up to 120 days after harvest. Of the abnormally ripening tomatoes investigated, including "Never ripe" (Nr Y a h, Nr c 12 r), "Evergreen" (gf r) and "Green Flesh" (gf), only rin did not show a typical climacteric and ethylene rise.Fruits from F1 plants resulting from reciprocal crosses between rin and normal plants apeared to ripen normally, but when compared to normal fruit, their ripening was delayed as measured by ethylene and C02 production and color change. These fruits produced only one-third to one-half as much ethylene at the peak of production compared to normal fruits.Exogenous ethylene or propylene treatment did not stimulate ethylene production by rin fruits but did stimulate C02 production. The C02 stimulation persisted only in the presence of the exogenous olefins. Stimulation of C02 production could be repeated several times in the same fruit. Wounding stress stimulated both ethylene and C02 production in rin fruits. It was concluded that rin tomato fruits behave like nonclimacteric fruits.catalytically (6,19). Propylene treatment of these fruits stimulates both ethylene production and respiration (19).In climacteric fruits, ethylene is generally considered to be the trigger of the ripening syndrome (21), and its presence at proper levels has been shown to be necessary for normal ripening (7, 16).Normal tomato fruits have been shown to be of the climacteric type (2,8,10, 27,28), and the response of tomato fruits to ethylene treatment has been investigated (15, 22). As in other tissues (1,17,18,26), tomato fruits respond to wounding stress by greatly increased ethylene and CO2 production (20).Reports concerning abnormally ripening tomato mutants have been published (13,14,24). Of special interest is the rin tomato mutant described by Robinson and Tomes (25) as a spontaneous mutation in a breeding line. Fruits of the rin mutant remain green while normal fruits ripen and turn red. The mutant eventually turns a lemon color with little or no lycopene development. Genetic analysis showed that rin was a monogenic recessive determined characteristic with no linkage associations except large sepal size. Little work has been done on the physiology or biochemistry of these ripening mutants (11). The respiratory and ethylene production behavior of the rin tomato mutant is described in this report. MATERIALS AND METHODSBiale (4) 6242.Plants of the F5 generation of rin and the normal breeding line (61-37, Fireball X Cornell 54-149) from which it originated were grown in the greenhouse (15 C night, 20 C day) and trained to a single stem. Flowers were tagged at anthesis with only one flower (lst or 2nd) per cluster being pollinated. All others in a cluster were excised. Fruit load per plant was limited to 8 to 10 fruits. Fruits were harvested 30 days after anthesis, the stems were removed carefully, and fruits were washed in water and dried with paper towels. Fruits of similar size were used for all tr...
Sex expression in cucumber (Cucumis sativus L.) and muskmelon (C. melo L.) was correlated with endogenous ethylene production. Plants of gynoecious (all female) sex types of the two species produced more ethylene than monoecius (male-female) plants. Sex expression in cucurbits is influenced by genetic, environmental, and hormonal factors. Monoecious strains of cucumber (Cucumis sativus L.) and muskmelon (C. melo L.) bear staminate (male) and pistillate (female) flowers. Gynoecious strains normally produce only pistillate flowers. Other cucumber and muskmelon strains produce staminate or pistillate and, in addition, perfect (hermaphroditic) flowers in various combinations. For example, andromonoecious strains are those that begin with staminate flowers and, eventually, also produce hermaphroditic flowers. Exogenous application of auxin (1, 2) and inhibitors of gibberellin biosynthesis (3) promote monoecious strains to form pistillate flowers, that is, increase femaleness. Application of gibberellin promotes formation of male flowers in monoecious and gynoecious phenotypes of cucumber (4, 5). Sex expression can be modified by daylength and temperature. Generally, short days and cool temperatures favor femaleness, while long days and high temperatures favor maleness, although there are exceptions (6). Determinations of endogenous growth substances indicate that strains with genetically strong female sex expression contain more auxin (7) and less gibberellin-like substances (8) than strains with strong male sex expression. There are certain differences between species; for example, gibberellin application does not cause male flower formation in gynoecious muskmelon (9). However, the results obtained with hormone applications and hormone determinations suggest the hypothesis that sex expression in cucurbits is controlled by an endogenous auxin-gibberellin balance (3, 7, 8, 10).Ethylene and 2-chloroethylphosphonic acid (ethephon), an ethylene-releasing compound, have recently been shown to promote femaleness in cucurbits (11, 12); thus, the effect of ethylene is similar to that of auxin. Exogenous application of auxin increases ethylene production by cucumber plants (13
The proportion of labeled (14)C-glycerol incorporated into phospholipids and the fatty acid composition of three phospholipids in germinating seeds and seedlings of chilling-sensitive lima beans (Phaseolus lunatus L.) and chilling-resistant broad beans (Vicia faba L.) and peas (Pisum sativum L.) at 10 and 25 C were determined. During the imbibition of seeds (first 24 hours), lima beans were sensitive to chilling injury at 10 C and a higher proportion of label was incorporated into phosphatidylethanolamine and phosphatidylglycerol than in broad beans and peas. Broad beans and peas incorporated a higher proportion of label into phosphatidylcholine. The oleic acid content of phosphatidylcholine was higher and linolenic acid content was lower in peas and broad beans than in lima beans at 10 and 25 C. The unsaturated to saturated fatty acid ratio was much higher for the chilling-resistant seeds than for the chilling-sensitive ones. In the seedling stage, the proportion of label incorporated into the four major phospholipids was similar in the three species regardless of temperature treatment. The fatty acid content of the phospholipids examined was not different in the three species in the seedling stage.
Nine wild tomato species were surveyed for variability in ripening characteristics. External signs of ripening, age of fnrit at ripening, and ethylene production patterns were compared. Ethylene production was monitored using an ethylene-free air stream system and gas chromatography. Based on these ripening characteristics, the fruits feil into three general categories: those that change color when they ripen, green-fited species that abscise prior to ripening, and green-fnlted species that ripen on the vine.The fruits that change color, Lycopersicon culentum var. ceraifoime, Lycopersicon punpinlliun and Lycopersicon cheesnmuii, exhibited a peak of ethylene production similar to the cultivated tomato; there were differences, however, in the timing and magnitude of the ethylene production. Peak levels ofethylne production are correlated with age at maturity. For the two species that abscise prior to ripening, Lycopersicon chiense and Lyicopersion peuianwn, abity to produce ethylene varied with stage of maturity. The two species differed from each other in time of endogenous ethylene production relative to abscission, suggesting differences in the control mechanisms regulating their ripening. For two of the green-frudted species that ripen on the vine, Lycopersicon chmkikwskii and Lycopericon paryiJiorm, ethylene production was correlated to fruit softening. For Lycopersicon hirsatum and Solanum penwelii, however, ethylene production was not correlated with external ripening changes, making questionable
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