Roden J, Van Volkenburgh E, Hinckley T M
Botany Department, University of Washington, Seattle, WA 98195, USA.
Tree Physiol. 1990 Jun;6(2):211-9. doi: 10.1093/treephys/6.2.211.
During the summers of 1986 and 1987, stem and leaf growth were measured on coppiced plants of Populus trichocarpa Torr. & A. Gray, P. deltoides Bartr. ex Marsh, and P. trichocarpa x deltoides growing in the field in Puyallup, WA. The trees were either irrigated periodically throughout the season, or grown without irrigation. In both treatments, stem volume at the end of the growing season was directly proportional to total leaf area in all three genotypes. The rate of individual leaf growth was reduced by lack of irrigation more in the parental species than in the hybrid. Only in the parental species did unirrigated trees have lower leaf water potentials (predawn and midday) than irrigated trees. However, stomatal conductances of all three genotypes were lower in unirrigated trees than in irrigated trees. Osmotic potentials of growing leaves of all three genotypes were also lower in unirrigated trees than in irrigated trees. As a consequence, turgor of growing leaves was as great in unirrigated trees as in irrigated trees, which indicates that turgor differences cannot explain the lower rates of leaf growth in the unirrigated trees. However, cell wall extensibility of leaves was lower in unirrigated trees than in irrigated trees, and the difference was greater in the parental species than in the hybrid. Unlike its effect on leaf area growth, irrigation increased stem volume growth of the hybrid and the parental species by a similar amount (12-16%).
在1986年和1987年的夏季，对华盛顿州皮尤拉普野外生长的毛果杨（Populus trichocarpa Torr. & A. Gray）、三角叶杨（P. deltoides Bartr. ex Marsh）以及毛果杨与三角叶杨的杂交种进行了萌条和叶片生长的测量。这些树木在整个生长季节要么定期灌溉，要么不灌溉。在这两种处理方式下，所有三种基因型树木在生长季节结束时的干材体积与总叶面积成正比。与杂交种相比，亲本树种中灌溉不足对单叶生长速率的降低影响更大。只有亲本树种中，未灌溉树木的叶水势（黎明前和中午）低于灌溉树木。然而，所有三种基因型的未灌溉树木气孔导度均低于灌溉树木。所有三种基因型生长叶片的渗透势在未灌溉树木中也低于灌溉树木。因此，未灌溉树木中生长叶片的膨压与灌溉树木中的一样大，这表明膨压差异无法解释未灌溉树木中叶生长速率较低的原因。然而，未灌溉树木叶片的细胞壁伸展性低于灌溉树木，且亲本树种中的差异比杂交种中的更大。与对叶面积生长的影响不同，灌溉使杂交种和亲本树种的干材体积生长增加了相似的幅度（12% - 16%）。
