STUDY OF PACLOBUTRAZOL ON MANGO (MANGIFERA INDICA L.) CV. KHIEW SAWOEY. I. EFFECT ON GIBBERELLIN-LIKE SUBSTANCES IN TERMINAL SHOOT AND FLOWERING

摘要

Paclobutrazol was applied as a soil drench at the rate 2, 4 and 8 g.ai. per tree, to 3 year old Khiew Sawoey mango trees. The treatments resulted in the reduction of shoot elongation by 12.7, 17.3 and 31.2 % respectively. Leaf area was also reduced by15.9, 18.9 and 19.7 %. Paclobutrazol markedly increased flowering up to 7.0, 11.0 and 11.3 folds in trees receiving 2, 4 and 8 g.ai. respectively. This increase in flowering was paralleled to the rapid decrease in endogenous gibberellin content in the shoot tip. Regardless to the treatments, mango tree started to flower when gibberellin content in the shoot tip decreased to an undetectable level, and tree treated with higher concentration of paclobutrazol flowered earlier than those treated with lowerconcentrations.