Christopher B. Watkins
Several phases are recognized in the development of horticultural crops from initiation of growth to death of a plant or plant part. These are growth, maturation, physiological maturity, ripening, and senescence. Watada et al. (1984) define useful terminology for these developmental stages for understanding fruit maturity. "Growth" is the irreversible increase in physiological attributes (characteristics) of a developing plant or plant part. "Maturation" is the stage of development leading to the attainment of physiological or horticultural maturity. "Physiological maturity" is the stage of development at which a plant or plant part will continue ontogeny, even when detached. "Ripening" is the composite of the processes that occur from the latter stages of growth and development through the early stages of senescence that results in characteristic aesthetic and/or food quality, as evidenced by changes in composition, color, texture, and other sensory attributes. "Senescence" involves those processes which follow physiological maturity and lead to death of tissue. The developmental stages overlap; those between maturity, ripening, and senescence are particularly important in a discussion of temperate fruit maturity, as these events can be temporally close.
An additional term that is used in discussion of maturity is "horticultural or harvestable maturity." This is a relative term representing a stage of development when a plant possesses the prerequisites for utilization by consumers for a particular purpose. Thus, many commodities may be harvested when physiologically immature. Temperate fruit, however, usually are harvested when fully developed and physiologically mature. At the time of harvest, ripening may also have occurred, but additional ripening can be required to meet consumer requirements. A mature fruit can be defined as one that has reached a stage in its growth and development cycle that, after harvesting and postharvest handling (including ripening, when required), will be at least the minimum quality acceptable to the consumer (Reid, 1992). Immature fruit may not ripen to meet flavor requirements of the consumers. They also may be prone to the development of physiological disorders, for example, bitter pit and superficial scald in apples, shriveling and friction discoloration in pears, and chilling injury in stone fruit. Overmature fruit, in contrast, may have fuller flavor, but texture can be poor and storage periods restricted because of susceptibility to injury and decay. Disorders associated with overmaturity may also develop, including physiological disorders such as soft scald and watercore in the case of apples, and susceptibility to internal injuries associated with low oxygen or elevated carbon dioxide in the storage atmosphere in the case of apples and pears.
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