Flower bud growth and ovule longevity of plum (Prunus domestics L.) cultivars Italian and Brooks and the effects of fall-applied ethephon and of temperature were studied. Fresh and dry weights of terminal flower buds were measured at l-week intervals from 50 days to 1 day before bloom in 1988. Buds were also analyzed for N, P, K, Ca, and B. After bloom, ovule longevity was determined using a fluorescence method after staining with aniline blue. Ovule longevity was determined in 1990 using shoots excised at full bloom from untreated and ethephon-treated trees of both cultivars and held in growth chambers for 18 days at 5, 10, 15, or 20C. `Brooks' flower buds showed a higher accumulation of fresh and dry weight than `Italian', and ethephon reduced bud weights in both cultivars. Ethephon did not affect mineral content of flower buds of `Brooks', but `Italian' flower buds contained a higher concentration of Ca and a lower concentration of P when treated with ethephon. Boron content was higher in the ethephon-treated buds of `Italian' trees on some sampling dates. Ovule longevity was higher for `Brooks' than for `Italian' in both years. Ethephon treatment delayed ovule senescence in `Italian' flowers, but had little or no effect on `Brooks' flowers. Increasing temperatures induced faster ovule senescence in both cultivars. Chemical name used. 2-chloroethylphosphonic acid (ethephon).
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