Leaf water relations of Eucalyptus globulus ssp. globulus and E. nitens: seasonal, drought and species effects

Abstract

In August 1990, a 2-ha plantation was established in an area where rainfall (about 515 mm year(-1)) was insufficient to meet evaporative demand. On nine occasions between September 1991 and April 1993, pressure-volume curves were constructed for irrigated and rainfed Eucalyptus globulus ssp. globulus Labill. and E. nitens (Deane and Maiden) Maiden trees. During the experiment, rainfed trees experienced six periods when predawn water potential was significantly lower than that of irrigated trees. In early spring of 1991 and 1992, osmotic potentials at full turgor and turgor loss point in the irrigated E. nitens were significantly lower than at other times of the year, probably because of winter hardening. Water stress reduced osmotic potential and increased bulk elastic modulus in E. nitens, whereas the reverse occurred in E. globulus. However, treatment differences with respect to changes in osmotic and elastic properties were commonly overshadowed by interspecific differences. These were most apparent at the end of the sixth period of water stress when osmotic potentials at full and zero turgor were significantly higher and bulk elastic modulus and relative water content at turgor loss point were significantly lower in E. globulus than in E. nitens. We conclude that the drought-tolerance responses of E. globulus make it a more suitable species than E. nitens for establishment on sites where moderate water stress is experienced.

Drought conditioning improves water status, stomatal conductance and survival ofEucalyptus globulussubsp. bicostataseedlings

“…High bulk modulus of elasticity has been related to processes of cell maturation [34]. Decrease in tissue elasticity has been identified in several species of Eucalyptus as a mechanism contributing to turgor maintenance under drought conditions [15,56,57], and after drought periods during wintertime [15]. Recently Clifford et al [4] proposed that in species with high osmotic adjustment capacity, it is more advantageous to have rigid cell walls as these may facilitate the maintenance of cell integrity during the rehydration occurring after the drought ends.…”

“…Similarly, increases in tissue elasticity allow plants to lose more water before reaching turgor loss point [46]. Thus both physiological mechanisms may contribute also to better performance after plantation [3,56].…”

“…Its success as a plantation tree species has been attributed to its high productivity and superior pulping quality. During the establishment of blue gum, water deficiencies represent the main risk, causing growth reduction and affecting survival [33,41,56].…”

Variations saisonnières des hydrates de carbone, des cyclitols et des relations hydriques chez 3 espèces d’Eucalyptus de taxonomie contrastée, en plein champ et poussant sur un site commun

“…A number of studies that have investigated inter-specific variation of osmotic potential in eucalypt species e.g. E nitens and E. globulus (White et al, 1996), E. behriana and E. polyanthermos (Prior et al, 1999), E. microcarpa (Clayton-Greene, 1983;Prior et al, 1999), E. melliodora (Clayton-Greene, 1983) and E. camaldulensis, E. grandis, E. viminalis and E. tereticornis (Lemcoff et al, 1994) and eucalypt hybrids . However, only White et al (2000) has investigated the physiology of eucalypt species from contrasting "chemo-taxonomic" groups indentified previously .…”

<i>Eucalyptus</i> sp. seedling response to potassium fertilization and soil water.

“…Among plants species, examples of turgor maintenance is accomplished through the adjustment of the cellular elasticity (SOBRADO, 1986;WHITE et al, 1996) and reduction of the leaf's osmotic potential (CLAYTON-GREENE, 1983;MYERS and NEALES, 1986). The leaf water relationship is a good indication of the capacity of the Eucalyptus species to maintain growth, engage in gas exchange and water use.…”