Abstract. Protein synthesis by intact Bartlett pear fruits was studied with ripening as measured by flesh softening, chlorophyll degradation, respiration, ethylene synthesis, and malic enzyme activity. Protein synthesis is required for normal ripening, and the proteins synthesized early in the ripening process are, in fact, enzymes required for ripening. l"C-Phenylalanine is differentially incorporated into fruit proteins separated by acrylamide gel electrophoresis of pome fruits taken at successive ripening stages.

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

Carnation (Dianthus caryophyllus) flowers were exposed to 2^i/l ethylene and examined at intervals to determine the time course of wilting, decrease in water uptake, and increase in ionic leakage in response to ethylene. A rapid decrease in water uptake was observed about 4 hours after initiating treatment with ethylene. This was followed by wilting (in-rolling of petals) about 2 hours later. Carbon dioxide inhibited the decline in water uptake and wilting and this is typical of most ethylene-induced responses. Ethylene did not affect closure of stomates. Ethylene enhanced ionic leakage, as measured by efflux of 36CI from the vacuole. This was judged to coincide with the decrease in water uptake. Gassing flowers with propylene initiated autocatalytic ethylene production within 2.4 hours. Since the increase in ethylene production by carnations preceded the increase in ionic leakage and the decline in water uptake by several hours, it is apparent that the change in ionic leakage does not lead to the initial increase in ethylene production as reported (Hanson and Kende 1975 Plant Physiol 55:663-669) in morning glory but may explain the autocatalytic phase of ethylene production.The association of ethylene with senescence of flowers is widely recognized and carnation flowers have been thoroughly examined in this respect (13). As the cut flower approaches senescence, a dramatic rise in the rate of ethylene production occurs followed soon after by wilting of the petals. Senescence can be hastened by as little as 30 nl/l of ethylene (2, 15). The events taking place between the rise in ethylene production, or exposure to ethylene, and the development of visual symptoms remain obscure. Lieberman et al. (11) over-all length, and placed individually in 20-ml vials. Flowers were obtained from a local grower and experiments were begun on the day of harvest. Four flowers in a 10-liter desiccator with a CO2 scrubber (NaOH solution) comprised a treatment. Flowers were exposed to ethylene at 21AI/I for 0, 3, 6, 9, or 12 hr, after which they were ventilated with ethylene-free air at a rate of 100 ml/min for the remainder of the experiment. Flowers were observed at 1-hr intervals to determine the onset of wilting symptoms as judged by in-rolling of petals.Effect of Ethylene on Rate of Water Uptake. Cut flowers were fitted into a specially designed glass sphere in which the flower bud was maintained in the desired gas atmosphere while the stem was connected to a potometer (5) and water uptake was measured at 30-min intervals. The flowers were ventilated continuously with 2 ,ul/l ethylene in dry air or with ethylene-free at a flow rate of 40 ml/min.Effect of Ethylene on Stomatal Aperture of Carnation Sepals. Flowers were cut to 10 cm over-all length and treated with ethylenie in desiccators as described above. Flowers were removed at 3-hr intervals from each of four desiccators and the sepals were excised, frozen in liquid N2, and freeze-dried. Sections (4 x 4 mm) were sputter-coated with gold and the surface was observed ...

A rapidly induced, transitory increase in the rate of ethylene synthesis occurred in wounded tissue excised from actively growing regions of etiolated barley, cucumber, maize, oat, pea, tomato, and wheat seedlings.Cutting intact stems or excising 9-mm segments of tissue from near the apex of 7-day-old etiolated Pisum sativum L., cv. Alaska seedlings induced a remarkably consistent pattern of ethylene production. At Ethylene production increases in a wide variety of plant tissues subjected to stress induced by noxious chemicals (2), pathogenic organisms (19), ionizing radiation (1), water imbalance (23), or mechanical injury (16). Abeles (3) has reviewed stress ethylene production. Stress-induced increases in ethylene production occur minutes (8,10,12,17,24), hours (6,9,11,14,18), or days (7, 16,21,22) after presentation of the stress. Appropriate controls are necessary to ascertain whether rapid increases in the rate of ethylene evolution result from facilitated diffusion of endogenous ethylene through the newly exposed cut surfaces, or from induced synthesis. Burg and Thimann (5) showed that in sliced apples the initial surge in ethylene and CO2 evolution was the result of endogenous levels of these gases. Increased evolution of ethylene after a lag period suggested induced synthesis. This is supported by studies with inhibitors which established that protein synthesis is required during the long lag period preceding stress ethylene synthesis (2, 6).Little work has been reported on the kinetics of rapidly induced ethylene production from stressed tissue (10,11 presents a detailed kinetic study of ethylene production from mechanically injured tissue during the first 4 hr after excision. MATERIALS AND METHODSPreparation of Plant Material. Seeds of Pisum sativum L., cv. Alaska were imbibed in aerated tap water for 6 hr at 23 ± 2 C and planted in moist vermiculite. All subsequent manipulations were performed in the dark or under dim green light. The growth cabinet was maintained at 24 ± I C and continuously flushed with humidified ethylene-free (

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Experiments were performed to determine the source(s) of ethylenecausing epinasty in flooded tomato plats (Lyc_perskoa escultm MilL). Simultaneous measurements were made of ethylene synthesized by the roots and shoots of tomato plants exposed to This study tested these hypotheses by using N2 ventilation of the root zone, rather than flood water, to impose an 02 deficiency upon the root without blocking gas diffusion. Microbial contribution of ethylene was prevented by using inert growing media. A special apparatus maintained the desired atmosphere in the root zone and allowed simultaneous measurement of root and shoot ethylene synthesis.

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