Fundamental study on the dendrochronology in tropical trees.

为了最终建立热带树木的年代学，我们进行了三项基本调查，以获得生长年轮结构与树木生长之间的关系。以生长于泰国季节性森林的camaldulensis等和生长于马来西亚热带雨林的Shorea acuminata等形成层结构的季节特征为研究对象。对形成层结构的季节性特征观察表明，即使在泰国旱季中期，形成层也表现出细胞分裂的结构。这被认为是生长环边界不清晰的原因之一。伸长生长与径向生长及生长环形成的关系。以巴西橡胶树和马来合欢幼树为研究对象。每两周测量一次伸长和径向生长，同时进行物候观察，特别是叶片的物候观察。生长环是在巴西螺停止伸长生长后形成的。而mangium的伸长生长与生长环的关系不太明确。部分人工林生长年轮结构分析。以典型人工林树种和人工栽培的龙心科树种为试验对象。在各种属的花盘上均观察到与生长期相对应的环状结构。然而，在某些物种中，它非常微弱或沿着圆周不连续。光镜下细胞生长环边界结构清晰，即纤维壁多呈增厚结构。虽然有些年轮被认为是所谓的“假年轮”，但在一些物种中，与年轮相对应的年轮得到了澄清。

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.