Fundamental study on the dendrochronology in tropical trees.

以建立热带树木年轮学为最终目标，开展了三项基础性研究，以获得树木年轮结构与树木生长的关系.以生长在泰国季节林的赤桉（Eucalyptus camaldulensis）等和生长在马来西亚热带雨林的尖叶山龙眼（Shorea acuminata）为材料，研究了形成层结构的季节特征。形成层结构的季节性特征的观察澄清，形成层显示细胞分裂的结构，即使在干燥的季节中期在泰国。这被认为是生长轮边界不明显的原因之一.以橡胶树和马占相思幼树为试材，研究了橡胶树幼树伸长生长与径向生长及年轮形成的关系。每两周测量一次伸长和径向生长，并进行物候观察，特别是叶片。生长轮形成后，停止在H.brasiliensis的伸长生长。马占相思的伸长生长与生长轮的关系不明显.几种种植园树木年轮结构的分析以典型种植园树木和龙脑香科人工林树木为材料。在每个种的花盘中都观察到与生长轮相对应的环状结构。然而，在某些物种中，它非常微弱，或者沿着圆周沿着不连续。生长环状结构的一部分与另一个环相连，光学显微镜下生长环边界的细胞结构清晰，即纤维壁在大多数情况下呈增厚结构。虽然有些年轮被认为是所谓的“假年轮”，但在一些物种中，与年轮相对应的生长轮被澄清。

Aiming to the final goal to establish the dendrochronology in tropical trees, three fundamental investigations to get the relationship between growth ring structure and tree growth were carried out.1. Seasonal characteristics of cambial structureEucalyptus camaldulensis etc. grown in seasonal forest in Thailand and Shorea acuminata grown in tropical rain forest in Malaysia were used for the investigation. The observation of seasonal characteristics of cambial structure clarified that cambium showed the structure of cell division even in the mid dry season in Thailand. This is considered to be one of the reasons for the indistinctness of the growth ring boundary.2. Relationship between elongation growth and radial growths and growth ring formation.Young trees of Hevea brasiliensis and Acacia mangium were used for the study. Elongation and radial growths were measured every two weeks together with the phenological observation especially of leaves. The growth rings were formed just after the cessation of elongation growth in H.brasiliensis. A.mangium, however, showed not so clear relationship between elongation growth and growth ring.3. Analysis of growth ring structure in some plantation grown trees.Some typical plantation trees and plantation grown Dipterocarpaceae trees were used for the experiments. In the disk of each species ring structures which corresponded to growth ring were observed. In some species, however, it was very faint or was not continuous along the circumference. A part of growth ring-like structure joined another ring, In the light microscopy cell structure of growth ring boundary was clarified, that is fiber wall showed thickened structure in most cases. Although some of the growth rings were considered to be so-called "false annual ring", growth ring which corresponded to annual ring was clarified in some species.