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Open access

S. F. Yang

Abstract

Ethylene has long been known to have a profound effect on plants (1). The early use of smoke or of burning incense as a ripening agent is undoubtedly attributable to the ethylene content. Following the advent of sensitive gas chromatographic instruments in the early 1960's, postharvest physiologists established the essential role of ethylene as a ripening hormone (1, 30). Demonstration of the natural function of ethylene in fruit ripening has stimulated the search for other functions. As the realization has grown that ethylene is a naturally produced plant hormone, so has the list of processes which it is known to regulate. The various effects of ethylene on plants or plant parts include growth inhibition, root initiation, fruit degreening, flower initiation, modification of flower sex expression, stimulation of fruit growth, initiation of fruit ripening, participation in plant disease resistance, promotion of leaf, flower and fruit abscission and dehiscence, release of seed and bud dormancy, release of apical dominance and regulation of tissue proliferation. At each stage of crop production, ranging from germination and propagation to harvest and postharvest handling, there are plant processes subject to modification by ethylene.

Open access

O.L. Lau, Y. Liu, and S.F. Yang

Abstract

Prior to 25 Oct., about 4-6 weeks (1983) or 3-5 weeks (1984) after the normal commercial harvest period, 1-aminocyclopropane-l-carboxylic acid (ACC), ethylene-forming enzyme (EFE), and internal ethylene concentration (IEC) in ‘Golden Delicious’ (Malus domestica Borkh.) apples attached to the tree were low. Thereafter, they began to increase rapidly. The increase in both ACC and IEC was earlier in detached preclimacteric fruit than in fruit attached to the tree. The increase of EFE coincided with that of IEC in detached fruit kept at 20°C. Attached fruit subsequently attained a higher level of ACC but a lower level of IEC as compared to the detached fruit. The results suggest that inhibitor(s) supplied from the tree not only delayed the accumulation of ACC in the fruit but also greatly inhibited its subsequent conversion to ethylene. Once the ripening process is initiated, the development of EFE precedes the development of ACC synthesis in both attached and detached fruit. Since attached fruit showed a steady loss of flesh firmness, green skin color, and starch, these changes did not appear to be related directly to the levels of ACC and internal ethylene. Detached fruit stored at 0° accumulated ACC and increased IEC slightly earlier than those stored at 20°. The magnitudes of these increases during subsequent storage at 0° were, however, smaller than those at 20°.

Open access

M. Yamaguchi, Celia Wang Chu, and S. F. Yang

Abstract

Radioactive (2–chloroethyl)phosphonic acid (ethephon) was applied to leaves and fruits of ‘Tiny Tim’ tomato and ‘Pioneer’ cucumber and to seedlings of ‘Yellow Crookneck’ summer squash. During the first day, slightly over 21% of the applied 14C-ethephon was converted to 14C-ethylene by the squash plants, and 10 to 15% was converted by the tomato plants. A week after treatment the rate of 14C-ethylene production decreased rapidly to less than 1% per day. Increases in rates of production of total ethylene following treatment were attributed to the decomposition of ethephon. Radioactive CO2 production was small, amounting to about 0.1% of the 14C applied.

Seven days following treatment of tomato leaves, about 15% of the 14C was translocated to developing fruits and lesser amounts to other parts of the plant. In the squash seedling, from 3 to 9% was translocated after 2 days from the site of application to other tissues. Twenty–five days after application to cucumber leaves, the fruits containted only 0.3% of the applied 14C–ethephon. In the tomato tissue the radioactivity was present as 14C–ethephon, but in the squash seedling tissue much of the radioactivity was present in a new compound.

Open access

O. L. Lau, Y. Liu, and S. F. Yang

Abstract

Firmness loss, increase in 1-aminocyclopropane-l-carboxylic acid (ACC) concentrations, and increase in internal ethylene concentrations were greatest in airstored fruit of ‘Golden Delicious’ apple (Malus domestica Borkh.) and lowest in controlled-atmosphere (CA)-stored fruit receiving a “rapid CA” or a “prestorage high carbon dioxide” storage procedure. Changes in apples kept in “slow CA” were intermediate. The accumulation of ACC in fruit was related closely to the subsequent flesh softening and increase in internal C2H4 concentration, and these processes were suppressed to different degrees in CA-stored fruit, depending on the storage procedures.

Free access

Philip E. Hammer, S.F. Yang, M.S. Reid, and J.J. Marois

The effectiveness of fungistatic atmospheres for postharvest control of Botrytis cinerea Pers. infections on cut rose flowers (Rosa hybrids L.) was investigated. Storing cut `Sonia', `Royalty', and `Gold Rush' roses at 2.5C with 10% CO2 for 5 days, followed by 2 days of cold storage in air, reduced the number of B. cinerea lesions that developed on inoculated and noninoculated flower petals by 77% and 82%, respectively, compared to cold storage for 7 days in air. Higher CO2 concentrations and longer CO2 treatment times reduced disease severity further, but resulted in unacceptable leaf discoloration on some cultivars. No deleterious effects of CO2-enriched storage atmospheres on flower quality, weight gain, or vase life were observed. Storage at 2.5C for 7 days in 2 μl SO2/liter reduced B. cinerea infections on inoculated and noninoculated flowers by 53% and 43%, respectively. No deleterious effects on flower quality, weight gain, or vase life were observed. Higher SO2 levels reduced disease severity further, but caused bleaching of the petal margins and necrosis around leaf wounds.

Open access

H.C. Wien, A.D. Turner, and S.F. Yang

Abstract

A series of field and greenhouse experiments was conducted with three cultivars of bell pepper (Capsicum annuum L.) to determine the hormonal basis for flower bud and flower abscission as induced by low light intensity (LLI). Imposition of 80% shade for 6 days increased abscission of reproductive structures by 38% and resulted in an increase in bud ethylene production. Concomitantly, bud reducing sugars and sucrose decreased and these were negatively correlated with ethylene levels and those of its precursor, ACC. Infusion of ACC into the pedicel resulted in flower bud abscission within 48 hr. The results indicate that ethylene is the primary causal agent of pepper flower bud abscission. Production of auxin by the bud plays a role in prevention of abscission. The abscission of disbudded pedicels was prevented by infusion of NAA. Although the three cultivars had similar responses to ACC, they differed in the amount of abscission under stress, bud sugar levels, and the time of onset of ACC and ethylene production. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC); α-napthaleneacetic acid (NAA); (2-chloro-ethyl)phosphonic acid (ethephon).

Open access

A. C. Cameron, C. A. L. Fenton, Y. Yu, D. O. Adams, and S. F. Yang

Abstract

Ethylene production of tissues excised from root, stem, leaf, inflorescence, and fruit of 16 plant species greatly increased following the application of 1-aminocyclopropane-1 carboxylic acid (ACC), an intermediate in the conversion of methionine to ethylene. Treatment with 1 mM ACC invariably increased the rate of ethylene production 10 to 1000 times over controls, whereas methionine at the same concentration was ineffective. Treatment with 0.1 mM ACC consistently increased ethylene production in all of the tissues tested, although only a few tissues responded to 0.01 mM.

Open access

Su Ling-Yuan, T. McKeon, D. Grierson, M. Cantwell, and S. F. Yang

Abstract

The changes in ethylene production rates and development of 1-aminocyclopropane-l-carboxylic acid (ACC) synthase and polygalacturonase (PG) activities were studied during the maturation and ripening of tomato fruit (Lycopersicon esculentum Mill, cv. ‘Castlemart’). There was a linear relationship between internal ethylene concentration and ethylene production rate; both increased exponentially as tomato fruit reached more advanced maturity and ripening. Thus, both of them correlate with the maturity and the ripening stages of tomatoes. A small increase in ACC synthase activity was observed at the early mature green stages which was followed by a marked increase at the breaker stage. ACC level followed the same pattern as ACC synthase activity. PG activity was undetectable or low throughout the mature green stages, but increased significantly after reaching the breaker stage. These data indicate that the onset of the development of ACC synthase activity precedes that of PG activity.