Decision factor of tree height - from viewpoint of water relations in trees

冲绳宫古岛琉球松平冠顶部针叶水分状况处于萎蔫边缘。从水分关系的角度探讨了绿竹平冠层的形成。从宫古岛的气候和地质条件来看，陆中对虾长期遭受严重的水分胁迫。此外，宫古岛经常受到巨大台风的袭击。显微镜下观察发现，许多伤口是由相互冲撞的分支造成的。染料溶液灌注试验结果显示，分支损伤部位的导水面积仅为健侧的1/2。由于伤口导致分支中的水力传导度降低，从而引起致死性水分亏缺。任何进一步的芽生长诱导芽由于萎蔫而枯死。这似乎导致了上层林冠的变平。

Needles water status on the top of flatted crown in Pinus luchuensis at Miyakojma Island, Okinawa, the subtropical region was on the verge of wilting. We addressed the flat canopy formation in P.luchuensis from the standpoint of water relations. Judging from climate and geology of Miyakojima Island, P.luchuensis constantly suffered from sever water stress. Further, Miyakojima Island often is attacked by huge typhoons. Microscopic study showed that many wounds were made by mutually rushed branch. As a result of dye solution perfusion test, water conducting area of wounded part of branch was restricted to 1/2 of that of sound ones. Reducing the hydraulic conductivity in branch due to wounds induced lethal water deficit. Any further shoot growth induces a shoot die back due to wilting. This seems to cause to flattening of the upper canopy.