Leaf water relations and stomatal behavior of four allopatric Eucalyptus species planted in Mediterranean southwestern Australia

Abstract

In 1986, four allopatric Eucalyptus species (E. camaldulensis Dehnh, E. saligna Smith, E. leucoxylon F. Muell and E. platypus Hook.) were planted together in a 480-mm rainfall zone, in 8-m wide contour belts as part of a plan to minimize waterlogging and secondary salinization. Throughout 1997, 1998 and 1999, there was significant inter-specific variation in predawn leaf water potential (Psi(pd)); however, maximum stomatal conductance (g(sm)) only differed significantly between species in mid to late summer. Relationships between g(sm) and Psi(pd) were significant and showed that stomata of E. camaldulensis were significantly more sensitive to Psi(pd), and presumably soil water potential, than stomata of E. leucoxylon or E. platypus. When applied to the Psi(pd) data, these relationships predicted that g(sm), and by inference transpiration, varied much less between species than Psi(pd). Diurnal measurements throughout the season confirmed this prediction, and showed that E. camaldulensis and E. saligna avoided drought by gaining access to deeper water, whereas E. leucoxylon and E. platypus maintained greater g(sm) at a given water stress than E. camaldulensis or E. saligna. Osmotic potentials measured after rehydration and water release curves of the leaves indicated that different mechanisms accounted for the apparent drought tolerance of E. leucoxylon and E. platypus. In summer, E. leucoxylon reduced osmotic potential at full and zero turgor by similar amounts compared with winter. In summer, E. platypus had a significantly lower bulk elastic modulus and relative water content at turgor loss point than E. camaldulensis, E. saligna or E. leucoxylon. This elastic adjustment resulted in a larger difference between osmotic potential at full and zero turgor in summer than in winter. The inherently low osmotic potential in E. leucoxylon and elastic adjustment in E. platypus resulted in turgor loss at a similar and significantly lower water potential than in E. camaldulensis or E. saligna. These results have implications for species selection for planting to manage groundwater recharge in areas prone to waterlogging and secondary salinization.

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

“…Physiological changes can include osmotic adjustment, elastic adjustment and stomatal regulation [9,10,40,59]. Osmotic adjustment, which allows plants to maintain turgor through the net accumulation of solutes, facilitates turgor-dependent processes such us stomatal opening and gas exchange under stressful conditions [30,46,57]. Similarly, increases in tissue elasticity allow plants to lose more water before reaching turgor loss point [46].…”

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

“…Previous investigations into field grown eucalypts have investigated trees often showing larger variations in Ψ, probably corresponding to more severe drought stress (e.g. Arndt et al, 2008;White et al, 2000). Our results offer an opportunity to investigate the potential acclimatory responses of plant metabolism to moderate seasonal fluctuations in water availability.…”

“…For eucalypts, the adjustment of internal osmotic potential in response to saline and/or dry conditions has been demonstrated across many species (ClaytonGreene, 1983;Lemcoff et al, 1994;Li, 1998;Myers et al, 1986;Pita et al, 2001;Tuomela, 1997;White et al, 2000). Variation among eucalypt species in the capacity to modify osmotic potential has been proposed to explain differing salt (Grieve et al, 1999) and drought (Li, 1998) tolerances, leading to suggestions of its use as a selection criterion (Lemcoff et al, 1994;van der Moezel et al, 1991).…”

“…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 . Based upon physiological assessments (water potentials, gas exchange and osmotic relations), results of that study suggested that four eucalypt species (E. camaldulensis, E. saligna, E. melliodora and E. platypus) possess contrasting mechanisms for tolerating water deficit.…”

Wheat water use and yield under different salinity of irrigation water

“…The accumulation of solutes may allow plants to maintain a positive pressure potential, which is required to keep stomata open and to sustain gas exchange and growth [WHITE et al 2000].…”