| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作研究所 === 92 === The purpose of this study was to investigate the effects of leaf development and chemicals on flowering in longan and understand the differences of continuous flower-inducing treatments. Longan trees were treated by potassium chlorate with various methods either in the field and potted plants. The results showed treatments of KClO3 with soil drench were more effective than leaf-spraying. The average percent of flowering with KClO3 solution was higher than KClO3 by soil drench only. The average percent of flowering treated with 4 % KClO3 was higher than 2 % KClO3 for the concentration of foliar-applying, however, application of 4 % was more unstable than 2 %. There was no flower formation in the potted longan despite any methods applied.
Leaf development in longan was classified into 4 different stages. Those were: (1) leaf just emerged, (2) brown leaf, (3) light green and (4) deep green. One of experimental objectives is try to find out the most effective timing of application and suitable developmental stages of leave for best flower induction. The result of field trials showed the longan trees could form flower buds in the leaf developmental periods of initiative emergence and deep green with soil treatments. Flower induction was found in any leaf stages with foliar application, and leaf index 1 was the most effective in treatments. The flowering of soil treatments were reduced slightly following continuous chemical application. The flowering percent was increased with higher concentration of foliar treatments.
The carbohydrates all were 10-15 % of dry weight (DW) before treatments and the levels were increased gradually following flower bud-forming but decreased at the period of full-opening bloom. Carbohydrates including soluble sugar and starch were no significant difference between treatments and control. Levels of soluble sugar were increased daily in the treatments of KClO3 solution and leaf-spraying after application. However, changes were unstable in the treatments of KClO3 only and control. Starch levels of all treatments increased rapidly but reduced gradually after application. Nitrogen levels did not change greatly before and after all treatments. Therefore, the changes of C/N ratio were similar to the carbohydrates in all treatments. Variation of carbohydrates was increased after treatments compared with before. During 90 days before the treatments, the levels increased continually with foliar treatments, but decreased with other ones during 60 days before the treatments. Variation of nitrogen decreased gradually following days. Variation of C/N ratio increased but decreased after treatments compared with before.
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