A DESCRIPTIVE MODEL OF THE SENESCENCE OF THE CARNATION (DIANTHUS CARYOPHYLLUS) INFLORESCENCE

There are two distinguishable forms of petal wilting in the carnation flower. One is caused by a temporary loss of turgour (reversible wilting) which is usually the result of a water stress, whereas the other (irreversible wilting) precedes death of the petals. The former is recognised by flaccidity of the petals to which turgour can be restored by relieving the water stress, and the latter by inrolling of the outer petals followed by progressive wilting of the inner petals. Irreversible wilting is accompanied by changes in the physiology of the petals, for example, increased permeability of the cells, an increase in respiration, and a characteristic surge in the production of ethylene (Smith, et al. 1964; Nichols, 1968a; Maxie, et al. 1973; Mayak and Dilley, 1976a). If the ethylene surge occurs during reversible wilting it must be relatively small and transient.

Broadly, the rise in ethylene signals the end of the display life (vase life) of the carnation flower. It can be caused or induced by exposure to exogenous ethylene, growth regulators, pollination (Nichols, 1968a, 1977), fungal infection (Smith, et al. 1964), abscisic acid (Mayak and Dilley, 1976b), or at the terminal phase as a result of natural ageing.

In contrast, certain chemical and physical treatments, for example, carbon dioxide (Smith and Parker, 1966; Nichols 1968a; Uota, 1969; Mayak and Dilley, 1976b), hypobaric storage (Mayak and Dilley, 1976b) or low concentrations of oxygen (Nichols, 1968a) suppress or modify the ethylene surge. These treatments result in increased longevity of the flower and it is for this reason that endogenous ethylene has been assumed to play an important role in the senescence of the carnation flower.

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