Effects of Wounding on Respiration and Ethylene Production by Cantaloupe Fruit Tissue

Despite the difficulty of evaluating the effects of handling and wounding, tissue slices offer advantages for physiiological or biochemical tests where small quantities of uniform tissues are required. This paper provides information on behavior of tissue slices from cantaloupe fru,its, including the changes induced by wounding. Respiration, ethylene production, and the effect of applied ethylene on respiration were measured, and the responses of tissue slices from cantaloupe fruits of various chronological ages were compared with the responses of matched intact fruits. It is well-known that wounding of plant tissue increases the rate of respiration (1, 5, 16), and may induce chemical changes and meristematic activity in the region of the wound (2, 3). Even shaking or dropping can cause an increase in respiration in avocado and citrus fruits (1, 9). Much information has been accumulated on changes in tissue cut from tubers and tuberous roots (12, 13, 15), but information on cut or wounded tissue from fruits is limited. The response of fruit tissues to wounding is variable and is influenced by varieity and maturity (1, 10, 19, 20, 24). Other sources of variability are fruit size, morphology, and the permeability of the peel to gases. According to various authors (1, 10, 22), increased CO2 evolution soon after cutting may indicate improved ventilation of the organ, rather than a direct effect of the wound on the cells involved. At least part of the burst of CO2, produced by apples immediately after cutting, may be eliminated by pre-evacuation of the tissue (5). Studies by Burg and Thimann (7) and Burg (5) emphasized the importance of the time elapsed after cutting in interpreting the effects of wounding. Cutting or wounding generally causes increased production of ethylene and -other volatiles by fruit tissue (11, 18). However, although Burg and Thimann (7) found an increased respiratory rate in tissues cut from postclimacteric apples, the rate of ethylene production was the same in plugs of tissue as in whole fruits, and the production by slices was appreciably lower. Release of existing ethylene fr'onj tissues may account for most of any increased production apparent just after cutting (5). When apple tissue was soaked in water or hypotonic solutions, Burg and Thimann (7) found that ethylene production was depressed, but the respiration rate was not affected; hypertonic solutions prevented the inhibition of ethylene production. Even during short periods of immersion, apple tissue loses appreciable amounts of fresh and dry weight (7, 10). Only avocado, banana, and tomato fruit tissues have been reported as stored for more than 2 days (1, 4, 5,). Avocado and banana tissue portions. showed normal ripening changes when stored in moist air, but such were not reported for tomato tissue. Infection by microorganisms may be a factor in the increased res,piration and ethylene production rates shown by cut tissue. While Petiicillkum digitatumii is the only microorganism known to produce relatively large amounts of ethylene (26), Williamson (25) has found that the growth of disease organisms may stimulate ethylene production by several plant materials; this response, which he attributed to injury, occurred as long as the infected tissue was alive. The following factors must be considered in the planning and interpretation of studies on ethylene production and respiration rate when fruit tissue slices are used: possible detrimental effects from washing or from immersion of the tissue in water, the length of time between cutting the tissue and the measurement of respiration and ethylene production rates, potential contamination from microorganisms, and the state of fruit maturity or ripeness.