CHANGES IN DORMANCY AND SENSITIVITY TO VERNALIZATION IN AXILLARY BUDSOF SATSUMA MANDARINE EXAMINED IN-VITRO DURING THE ANNUAL CYCLE

Effect of season and the presence of fruit on bud-endodormancy and the flowering response to low temperature treatments were determined usin g bud cultures of Owari satsuma mandarin (Citrus unshiu Marc). Bud dor mancy was deeper in fruiting as compared to defruited trees. In fruiti ng trees, the intensity of bud dormancy was highest in spring, decreas ed to a low value by early Jul. and then increased until early winter. This increase in dormancy during summer and early autumn did not occu r in non-fruiting trees. No flowers formed in buds cultured between Ma y and Sep. Both in fruiting and defruited trees, buds became competent to show a vernalization response to chilling by the end of Oct., at t he time they also became capable of sprouting in vitro at low temperat ure (15/10 degrees C). There was a direct effect of fruit on the buds which persisted long after fruit removal and resulted in a reduction o f the flowering response to chilling. (C) 1995 Annals of Botany Compan y