Tissue-water relations of two co-occurring evergreen Mediterranean species in response to seasonal and experimental drought conditions

Abstract

Tissue-water relations were used to characterize the responses of two Mediterranean co-occurring woody species (Quercus ilex L. and Phillyrea latifolia L.) to seasonal and experimental drought conditions. Soil water availability was reduced approximately 15% by partially excluding rain throughfall and lateral flow (water runoff). Seasonal and experimental drought elicited physiological and morphological adaptations other than osmotic adjustment: both species showed large increases in cell-wall elasticity and decreased saturated-to-dry-mass ratio. Increased elasticity (lower elastic modulus) resulted in concurrent decreases in relative water content at turgor loss. In addition, P. latifolia showed significant increases in apoplastic water fraction. Decreased saturated-to-dry-mass ratio and increased apoplastic water fraction were accompanied by an increased range of turgor maintenance, which indicates that leaf sclerophyllous traits might be advantageous in drier scenarios. In contrast, the degree of sclerophylly (as assessed by the leaf mass-to-area ratio) was not related to tissue elasticity. An approximately 15% reduction in soil water availability resulted in significant reductions in diameter growth when compared to control plants in both species. Moreover, although P. latifolia underwent larger changes in tissue water-related traits than Q. ilex in response to decreasing water availability, growth was more sensitive to water stress in P. latifolia than in Q. ilex. Differences in diameter growth between species might be partially linked to the effects of cell-wall elasticity and turgor pressure on growth, since Q. ilex showed higher tissue elasticity and higher intrinsic tolerance to water deficit (as indicated by lower relative water content at turgor loss) than P. latifolia.

California perennial grasses are physiologically distinct from both Mediterranean annual and perennial grasses

“…Conditions of high soil water availability may limit the explanatory power of the plant-water physiological measurements reported in this study, as many of them are known to be strongly affected by water availability (Hinckley et al 1980;Davis and Mooney 1986;Rhizopoulou and Mitrakos 1990;Abril and Hanano 1998;Salleo and Nardini 2000;Serrano et al 2005;Galmes et al 2007). Thus, the values reported here may differ substantially from those that may be obtained under field (drier) conditions.…”

“…Thus, the values reported here may differ substantially from those that may be obtained under field (drier) conditions. While we would expect low water availability to alter the mean values of TRc, RWC tlp , Rh, SLW and Width for each guild, we would also expect dry conditions to increase the relative differences of these traits between guilds (Hinckley et al 1980;Davis and Mooney 1986;Rhizopoulou and Mitrakos 1990;Abril and Hanano 1998;Salleo and Nardini 2000;Serrano et al 2005;Galmes et al 2007). We then consider our measurements under well-watered conditions to be under estimates of drought tolerance for these species and a conservative estimate of differences in drought tolerance between guilds.…”

“…TRc for each species were determined gravimetrically from one large leaf from each of six individuals-generally the second youngest fully expanded leaf. Relative water content at turgor loss point (RWC tlp ) was then estimated from the graphs of cuticular transpiration rate over time (Serrano et al 2005).…”

“…In addition, Mediterranean climates differing in severity of summer drought may produce variable adaptive responses. We predict that grasses with different growth forms and life history as well as from regions with differing summer rainfall regimes, will exhibit different leaf ecophysiological traits (Hinckley et al 1980;Davis and Mooney 1986;Rhizopoulou and Mitrakos 1990;Abril and Hanano 1998;Salleo and Nardini 2000;Serrano et al 2005;Galmes et al 2007).…”

Evaluación y comparación de las respuestas fenológicas, morfológicas y ecofisiológicas de 4 especies de Quercus típicas de los bosques del trópico seco (Paisaje Terrestre Protegido Miraflor-Moropotente – Nicaragua)

“…Foliar area and perimeter were determined from computer imaging of harvested leaves (Image Tool 3.0), and used to calculate Specific Leaf Weight (SLW) (gDW / m-2leaf) and Leaf Fractal Index (Foliar Perimeter / Foliar area-1) (Serrano et al 2005, Vaughn et al 2011.…”