ISHS Acta Horticulturae 398: Postharvest Physiology of Fruits
REGULATION OF FRUIT PHYSIOLOGY BY CONTROLLED/MODIFIED ATMOSPHERES |
| Author: | Adel A. Kader |
| Keywords: | Respiration, ethylene, low-O2 stress, elevated-CO2 stress, avocado, Persea americana, pear, Pyrus communis |
| Abstract:
Low O2 and/or high CO2 concentrations that do not cause physiological stress to fruit tissues reduce respiration and ethylene production rates and retard compositional changes associated with color, firmness, flavor and nutritional quality of fruits. Also, CO2-enriched atmospheres ameliorate chilling injury and other physiological disorders in some fruits and reduce incidence and severity of decay. Oxygen levels below 5% greatly reduce ethylene production of fruits by inhibiting ACC oxidase activity. While 1% CO2 or lower stimulate ethylene production, higher CO2 concentrations reduce it by inhibiting activities of ACC synthase and ACC oxidase. Cytoplasmic pH values (measured using NMR spectroscopy) are reduced by 0.2 to 0.6 pH units in 'Hass' avocado and 'Bartlett' pear fruit discs exposed to low O2 and/or high CO2 atmospheres. Such pH reduction influences the activity of many enzymes involved in respiratory metabolism, ethylene biosynthesis and compositional changes. Accumulation of acetaldehyde, ethanol, ethyl acetate, and/or lactate is enhanced by <0.5% O2 and/or >20% CO2. Preclimacteric fruits are both less stressed under such atmospheres and have greater potential for subsequent repair than postclimacteric fruits. | |
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