Impact of water stress on reproductive development of sweet peppers (Capsicum annuum L.). I. Role of ethylene in water deficitinduced flower abscission

H. Z. Jaafar, J. G. Atherton, C. R. Black and J. A. Roberts

Abstract

The study was carried out to examine the role of ethylene in accelerating flower abscission in sweet pepper. Water stress significantly increased ethylene evolution from sweet pepper flowers just before abscission to 40-fold greater than that measured before anthesis. Its evolution from the flowers also increased by up to eightfold compared with unstressed control plants. In unstressed plants, ethylene evolution from the flowers and leaves increased with age but the former always had lower evolution rate than the leaves suggesting that leaves may be the site for ethylene synthesis. In stressed plants, however, ethylene evolution from the flowers was threefold greater than that from the leaves, implying that the developing flowers were more sensitive to water stress. Sweet pepper flowers were capable of forming abscission lines at the base of the pedicels following exposure to elevated endogenous ethylene concentrations caused by water stress. However, mature pepper leaves were incapable of doing so. Shoot dry matter and its partitioning to the leaves and stems did not decline markedly during the period of increased ethylene evolution in the flowers, and therefore could not be correlated with the changing pattern of ethylene evolution. The reductions in assimilate production or partitioning to the leaves and stems were not directly involved in reducing flower abscission. All components of water potentials were decreased during periods of increased ethylene production, but these changes could not be consistently related to increased ethylene evolution from the flowers and leaves. The relatively large decreases in water relations components during progressive water stress may not be useful in predicting the changes in ethylene production which are effective in promoting abscission; instead these may be induced by much smaller losses in water status or turgor.

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