Myers B J, Robichaux R H, Unwin G L, Craig I E
CSIRO Division of Forest Research, 2600, Canberra, ACT, Australia.
Department of Ecology and Evolutionary Biology, University of Arizona, 85721, Tucson, AZ, USA.
Oecologia. 1987 Nov;74(1):81-85. doi: 10.1007/BF00377349.
Leaf water potentials, osmotic properties and structural characteristics were examined in the Australian tropical rainforest tree species, Castanospermum australe. These features were compared for individuals growing in the understorey and canopy of the undisturbed forest and in an open pasture from which the forest had been cleared. Leaf water potentials during the day declined to significantly lower values in the open-grown and canopy trees than in the understorey trees. During most of the day the opengrown tree experienced the lowest water potentials. These differences were paralleled by significant differences in tissue osmotic properties. The tissue osmotic potential at full hydration was lowest in the open-grown tree (-1.80 MPa), intermediate in the canopy trees (-1.38 MPa), and highest in the understorey trees (-0.80 MPa). As a result, the degree to which high and positive turgor pressures were maintained as water potentials declined was highest in the open-grown tree, intermediate in the canopy trees, and lowest in the understorey trees. The differences in tissue osmotic properties between individuals in the three crown positions were paralleled, in turn, by differences in leaf structual characteristics. Relative to leaves of the canopy and open-grown trees, leaves of the understorey trees had significantly larger epidermal cells with thinner cell walls, larger specific leaf areas and turgid weight: dry weight ratios, and a higher proportion of intercellular air space.
对澳大利亚热带雨林树种澳洲栗豆树的叶片水势、渗透特性和结构特征进行了研究。对生长在未受干扰森林的林下和树冠层以及森林已被砍伐的开阔牧场中的个体的这些特征进行了比较。白天，开阔地生长的树木和树冠层树木的叶片水势下降到显著低于林下树木的值。在一天的大部分时间里，开阔地生长的树木水势最低。这些差异与组织渗透特性的显著差异相对应。完全吸水时的组织渗透势在开阔地生长的树木中最低（-1.80兆帕），在树冠层树木中居中（-1.38兆帕），在林下树木中最高（-0.80兆帕）。因此，随着水势下降，保持高正膨压的程度在开阔地生长的树木中最高，在树冠层树木中居中，在林下树木中最低。三个树冠位置个体之间组织渗透特性的差异，反过来又与叶片结构特征的差异相对应。相对于树冠层和开阔地生长树木的叶片，林下树木的叶片具有明显更大的表皮细胞，细胞壁更薄，比叶面积更大，膨压重量与干重比更高，细胞间隙比例更高。
