外施脱落酸和赤霉素对海南岛落叶树木韧皮部的作用

将脱落酸（０．２％ＡＢＡ和１％ＡＢＡ羊毛脂）和赤霉素（０．５％ＧＡ３和１％ＧＡ３羊毛脂）涂到树干树皮的刮皮伤口上，经过８ｄ后用光学显微镜技术观察堵塞筛管的固定胶胝体在韧皮部中形成的位置，以确定有功能韧皮部的厚度。对于无叶期筛管破坏型的树种苦楝树（Ｍｅｌｉａ ａｚｅｄａｒａｃｈ Ｌ．），在生长季开始时期之后施用ＡＢＡ，能使有功能韧皮部大量减少，但在生长季开始时期施用，对韧皮部几乎没有作用；在生长季晚

Effects of Exogenous Abscisic Acid and Gibberellin on Phloem of Deciduous Trees on Hainan Island

To determine the effects of abscisic acid (ABA)and gibberellin (GA3), 0. 2 %ABA,1%ABA, 0. 5%GA,, 1 %GA, in lanolin were applied to scraped bark of the trunks of the deciduous trees on Hainan Island,and 8 days after application the thickness of functional phloem was measured by using light microscopy based on the location where definite callose blocking the sieve tube appeared. For Melia azedarach L.,a representative of the trees which have their sieve tube destroyed in leaf-absent period,ABA app1ication was found to reduce considerably the thickness of the functiona1 phloem in the period after the early growth,but to have little effect in the early growth period. GA, application resulted in inhibition of natural destruction of the functional phloem in the later growth period. Theeffect of ABA rather than GA, was shown when they were applied simultaneously oraltenately. For Hevea brasiliensis Mull. Arg.,a representative of the trees which have their sieve tubes maintained in leaf-absent period,ABA application caused a little decrease in functional phloem thickness either in the early or later period of growth. GA3 application had the same effect on Hevea brasiliensis phloem as that on Melia azedarach. ABA application experiments were also made on 3 species of trees with sieve tube destroyed in the leaf-absent period,including Camptotheca acuminate Decne. and 3 species of trees with sieve tubemaintained in the leaf-absent period,including Pterocarpus indicus Willd,and results were obtained similar respectively to those from the experiments on Melia azedarach and Hevea brasiliensis- Based on these results,it was suggested that ABA and GA3 might not be the primary factors which cause the differences of the phloem structure in the leaf-absent period between the two types of the trees represented respectively by Hevea bTasiliensis and Melia azedarach.