Growth and Respiratory Response of Fig (Ficus carica L. cv. Mission) Fruits to Ethylene

Abstract

Maxie and Crane (37) pointed out that "Before CMH can be established as a growth regulator in figs, it must be verified that production of the gas is correlated with the onset of renewed growth (Period III)." Evidence indicating the existence of such a correlation is presented here. MATERIALS AND METHODSCurves of growth in diameter were developed for both firstand second-crop fruits and were used for reference in timing of ethylene treatment and in fruit sampling. Diameters of 10 basal-most fruits on each of five 10-year-old trees were measured periodically with a vernier caliper. Sampling of treated fruits as well as controls was confined to the basalmost fruits. Average fresh and dry weights were determined by weighing triplicate five-fruit samples before and after drying at 60 C until weights remained constant.Ethylene (5 1ul/l in an air mixture) was applied to fruitbearing branches in the orchard. For this purpose, a 1900-liter tank was evaculated, a predetermined volume of ethylene gas was injected, and the tank was compressed to the appropriate pressure (about 110 kg/ cm2). Whole branches were enclosed in large polyethylene bags provided with an inlet and an outlet, and ethylene was introduced into them through Tygon tubing at the rate of 100 ml/min, as regulated by a flow meter (8). Other branches that were similarly treated with compressed air served as controls.Rate of respiration at different stages of fruit development was monitored using triplicate fruit samples, each consisting of 200 to 300 g. The samples were placed in 4-liter glass jars, the lids of which were tight and provided with two glass tubes that served as inlets and outlets. Respiration rate, measured as mg C02/kg fruit hr, was determined by the colorimetric method of Claypool and Keefer (8). The fruits were kept at 20 C, and the first measurement was made 24 hr after harvest, followed by daily measurement for the following 6 days.Changes were monitored in the concentration of endogenous C2H4, CO2, and 02 in the internal atmosphere of the fruits during development and following treatment. The gases were extracted from the fruits by the vacuum method described by Maxie et al. (38). Their concentrations were determined by gas chromatography (31,38).

Ethylene-stimulated Synthesis of Ribosomes, Ribonucleic Acid, and Protein in Developing Fig Fruits

“…A sharp rise in respiratory activity was noted after 24 hr of exposure to ethylene in vivo (7). Changes in color, texture, and an increase in fruit (7) and cell size (N. Marei and M. Bradley, in preparation) were first detected after 48 hr of continuous treatment.…”

“…Mission) fruits were sampled periodically during growth period II and following ethylene treatments (7). Ethylene (5 ul/liter in an air mixture with a flow rate of 100 ml/min) was applied to fruits still on the tree (in vivo treatment) using the procedure of Marei and Crane (7).…”

“…Mission) fruits were sampled periodically during growth period II and following ethylene treatments (7). Ethylene (5 ul/liter in an air mixture with a flow rate of 100 ml/min) was applied to fruits still on the tree (in vivo treatment) using the procedure of Marei and Crane (7). In vitro experiments consisted of the application of ethylene to fruit slices during a 6-hr incubation period by bubbling an ethylene/air mixture (5 1A/liter, flow rate of 25 ml/min) through the incubation medium.…”

“…

Ethylene profoundly stimulates the growth and ripening of fig fruits if applied during the second half of growth period II, the slow growth phase of the characteristic double sigmoid growth curve (7,9). Although ethylene-treated fruits ripened 2 to 3 weeks early, within 6 days from inception of treatment, they were indistinguishable from ripe, untreated fruits (7).

…”

Probing a Membrane Matrix Regulating Hormone Action

“…Suge (47) found that a low concentration of ethylene stimulated growth of intact oat and rice mesocotyls. Hirai et al (14), Maxie and Crane (30), and recently Marei and Crane (29) showed that ethylene markedly stimulated the enlargement and maturing of immature fig fruits. These are particularly germane observations, since fig ripening is the only other well substantiated situation in which lipids induce ethylene formation (13,14), and the fig fruit is anatomically derived from a stem.…”