Responses of leaves and shoots to environmental variables and tree growth

1.通过对气体交换和碳同位素的同步测定，我们证实了树木叶片，特别是万年青树木叶片中厚的叶肉细胞壁是光合CO_2扩散的一个相当大的障碍。厚度对于增加CO_2溶解的表面积是重要的。我们还发现栅栏组织细胞响应成熟叶片的信号进行平周分裂。成熟叶片在强光照射下，发育中叶片的栅栏组织细胞发生平周分裂，与发育中叶片的光照条件无关。叶片展开后光合速率最大。4.分析了确定水分关系的重要参数--体积弹性模量在成熟叶片中的变化规律。体积弹性模量下降响应于水分胁迫，使细胞膨压维持。这些变化是可逆的，并且比渗透势的变化快。5.我们应用管道模型理论的导数形式来描述树木的生长。光截获和长短枝分化是决定林木粗生长的重要因素。

1.By concurrent measurements of gas exchange and carbon isotope, we established that thick mesophyll cell walls in tree leaves, in particular those of evergreen trees, is a considerable barrier to photosynthetic CO_2 diffusion.2.We clarified why sun leaves should be thicker than shade leaves. Thickness if important for increasing the surface area for CO_2 dissolution. We also found that palisade tissue cells divide periclinally in response to signal from the mature leaves. When mature leaves are exposed to high light, palisade tissue cells in developing leaves divide periclinally irrespective of the light conditions of the developing leaves.3.We described development of photosynthetic activity in the leaves of evergreen tree species. The maximum photosynthetic rate was observed well after the full leaf expansion.4.We analyzed behavior of the bulk elastic modules, an important parameter for determining water relations, in mature tree leaves. Bulk elastic modules decreased in response to water stress so that cell turgor was maintained. These changes were reversible and quicker than changes in osmotic potential.5.We applied the pipe model theory in the derivative form to describe tree growth. Light interception and long and short shoot differentiation are important determinants of thickness growth of the trees.