Effect of Potassium Chlorate on Off-Season Flowering in Longan (Dimocarpus Longan)

The effect of potassium chlorate (KClO3) on off-season flower induction in 'Fenker' longan (Dimocarpus longan Lour.) was investigated. The percentages of budbreak in KClO3 treated plants were 100% in summer and 70% in autumn substantially higher than those in untreated plants which had 70% budbreak in summer and 6.2% in autumn. KClO3 treatment induced off-season flowering in both seasons. The best result was obtained by applying 2 g KClO3 in solution as soil drenching for each potted experiment plant. The flowering percentages of longan so treated in summer and autumn were 72.5% and 68.9%, respectively. The shoot viability of longan plants was not affected by KClO3 treatment in autumn, but the root viability of the plants 21 days after the KClO3 treatment was lowered. The total nitrogen concentration in the shoot of KClO3 treated plant was not significantly different from that of untreated plants when the chemical was applied in autumn, but was higher when applied in summer. The ethylene production in the shoots of treated plants was not significantly different from that of untreated ones measured throughout the experiment in autumn. The KClO3 did not significantly affect the starch concentration in shoots either in summer or in autumn. In contrast, KClO3 treatment significantly increased the total soluble sugar concentration in shoots when measured 21days after the treatment in summer as well as in autumn. The increase of total soluble sugar in shoots and the reduction of root viability in the treated plants might be the mechanism in enhancing floral induction.