Seasonal changes in endogenous gibberellin contents in satsuma mandarin [Citrus reticulata] during flower differentiation and the influence of paclobutrazol on gibberellin synthesis
1996
Ogata, T. (Osaka Prefectural Univ., Sakai (Japan). Coll. of Agriculture) | Hasukawa, H. | Shiozaki, S. | Horiuchi, S. | Kawase, K. | Iwagaki, I. | Okuda, H.
Seasonal changes of contents of endogenous GAs in vegetative organs and effect of harvesting date on endogenous GA synthesis were surveyed. Simultaneously, the influence of paclobutrazol, a gibberellin (GA) synthesis inhibitor, on the induction of flowering in satsuma mandarin was evaluated. (1) GA1 content in leaf of vegetative shoot increased from 26 July to 26 September, decreased to 28 January, and increased again to 24 March. On the contrary, GA20 and GA19-like activities were the lowest on 26 September; their maximum activities were recorded on 29 November and 28 January, respectively. The trends of GAs in the auxiliary buds were closely paralleled with those in the leaves. (2) A foliar spray with 1,000 ppm paclobutrazol on 1 February increased the numbers of flowers, and decreased GA20 and GA19-like activities in leaf, but it did not affect GA1 activity. (3) The early harvest in October increased the number of flowers the following season compared to the late harvest in December. GA20 activity in the leaves of the vegetative shoots on the early harvested tree was lower than those of the late harvested tree at the end of November and January. Thus, paclobutrazol treatment reduced the level of GA1 prcursor, but not GA1, which is in agreement with the metabolism of endogenous GAs in the early harvested tree. The inhibition of GA synthesis by paclobutrazol is one of the physiological evidence which indicate that GA plays a role in flowering in satsuma mandarin
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