© 1998 Heron Publishing—Victoria, Canada
Water deficits are more important in delaying growth than in changing patterns of carbon allocation in Eucalyptus globulus
J. Osório (1), M. L. Osório (1), M. M. Chaves (1) and J. S. Pereira (1, 2)
1. Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa codex, Portugal / 2. Author to whom correspondence should be addressed (jspereira@isa.utl.pt) / Received July 17, 1997
Summary
Potted cuttings of three Eucalyptus globulus Labill. clones (AR3, CN44, MP11) were either well watered or subjected to one of two soil water deficit regimes for six months
in a greenhouse. Reductions in lateral branching, leaf production and leaf expansion were the leading contributors to the
large differences observed in biomass production between well-watered and water-stressed plants. Although no significant differences
among clones were observed in dry matter accumulation or in the magnitude of the response to soil water deficits, sensitivity
of lateral branching, leaf initiation and whole-plant foliage to water stress was significantly lower in CN44 than in AR3
and MP11. When the confounding effect of differences in plant size resulting from the different watering regimes was removed,
allometric analysis indicated that the genotypes differed in biomass allocation patterns. In addition to a drought-induced
reduction in leaf number, water deficits also resulted in smaller leaves because leaf expansion was inhibited during dehydration
events. Resumption of leaf expansion following stress relief occurred in all of the clones, but was particularly evident in
severely stressed plants of Clone AR3, possibly as a result of the osmotic adjustment observed in this genotype.
Keywords:
acclimation, allocation, allometry, leaf elongation rate (LER), osmotic adjustment, plant growth, water relations, water stress.
