© 1990 Heron Publishing—Victoria, Canada
Cellular basis for limitation of poplar leaf growth by water deficit
J. Roden (1), E. Van Volkenburgh (1) and T. M. Hinckley (2)
1. Botany Department, University of Washington, Seattle, WA 98195, USA / 2. College of Forestry, University of Washington, Seattle, WA 98195, USA / Received June 16, 1989
Summary
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 × 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%).
