Changes in carbohydrate levels, alpha-amylase activity, indoleacetic acid and gibberellin-like substances in the summer shoots of wase satsuma mandarin [Citrus reticulata] trees grown indoors during flower-bud differentiation
1995
Yahata, D. (Fukuoka-ken. Agricultural Research Center, Chikushino (Japan)) | Oba, Y. | Kuwahara, M.
The mechanism of flower-bud differentiation in satsuma mandarin (Citrus unshiu Marc. var. praecox Tanaka) as related to changes in carbohydrate contents, alpha-emulous activity and levels of IAA and GA-like substances in the summer shoots of 6-year-old "Ueno Wase" trees grown indoors was investigated in autumn. 1) to determine when flower-bud differentiation occurred, excised summer shoots were defoliated,treated with 150 ppm BA, and then kept at 28 degrees C for 10 days with their bases in water. Shoots were treated from mid-October to early-December at a biweekly interval. Until mid-October, only vegetative shoots sprouted, whereas in early-November a considerable number of flowers emerged. Therefore, flower-bud initiation occurred to be in late-October. 2) Increase in starch content in the summer shoots coincided with the flower-bud initiation period. In contrast, sugar content decreased from mid-October to mid-November. Towards early December, starch content decreased n the leaf laminas and stems, while sugar accumulation accelerated in the laminas, petioles, buds, and stems. From these results, we proposed that flower-bud differentiation of satsuma mandarin has no direct correlation with the changes in carbohydrate contents in these parts of the shoots. 3) In summer shoots, alpha-amylase activity decreased in early-November and increased with the advance of flower-bud development. The activity in laminas was lower than that in petioles, buds, and stems but it fluctuated greatly throughout the investigation period. 4) During the flower-bud initiation period in late-October, endogenous GA-like substances in the buds of the summer shoots was higher than those in the petioles. IAA level in the buds was higher in mid-October than in mid-November
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