Plasticity in Vulnerability to Cavitation of Pinus canariensis Occurs Only at the Driest End of an Aridity Gradient

Abstract

Water availability has been considered one of the crucial drivers of species distribution. However, the increasing of temperatures and more frequent water shortages could overcome the ability of long-lived species to cope with rapidly changing conditions. Growth and survival of natural populations adapted to a given site, transferred and tested in other environments as part of provenance trials, can be interpreted as a simulation of ambient changes at the original location. We compare the intraspecific variation and the relative contribution of plasticity to adaptation of key functional traits related to drought resistance: vulnerability to cavitation, efficiency of the xylem to conduct water and biomass allocation. We use six populations of Canary Island pine growing in three provenance trials (wet, dry, and xeric). We found that the variability for hydraulic traits was largely due to phenotypic plasticity, whereas, genetic variation was limited and almost restricted to hydraulic safety traits and survival. Trees responded to an increase in climate dryness by lowering growth, and increasing leaf-specific hydraulic conductivity by means of increasing the Huber value. Vulnerability to cavitation only showed a plastic response in the driest provenance trial located in the ecological limit of the species. This trait was more tightly correlated with annual precipitation, drought length, and temperature oscillation at the origin of the populations than hydraulic efficiency or the Huber value. Vulnerability to cavitation was directly related to survival in the dry and the xeric provenance trials, illustrating its importance in determining drought resistance. In a new climatic scenario where more frequent and intense droughts are predicted, the magnitude of extreme events together with the fact that plasticity of cavitation resistance is only shown in the very dry limit of the species could hamper the capacity to adapt and buffer against environmental changes of some populations growing in dry locations.

Adaptations of white spruce to climate: strong intraspecific differences in cold hardiness linked to survival

“…K L was mostly regulated by needle area rather than by a change in hydraulic conductivity as we can see from the significant correlation between K L and A L : A X and the absence of a correlation between K L and K S (Table ). Similar findings were reported from studies on pine populations sampled across climate gradients (Lopez, Cano, Choat, Cochard, & Gil, ; Martínez‐Vilalta et al., ). At a particular transpiration rate ( E ), a branch with higher K L will be able to maintain a smaller water potential gradient (ΔΨ) than a branch with lower K L , because E = K L ΔΨ (Tyree & Zimmermann, ).…”

Adjustments and coordination of hydraulic, leaf and stem traits along a water availability gradient

“…Studies addressing ITV in hydraulic traits are less frequent (but see Martínez‐Vilalta et al ., ; Wortemann et al ., ; Lamy et al ., ; Hajek et al ., ). In line with our results, Hv and K L have been reported to be among the most plastic hydraulic properties in pines (DeLucia et al ., ; Martínez‐Vilalta et al ., ) whereas other traits such as P 50 usually show low plasticity (Maherali & DeLucia, ; Martínez‐Vilalta et al ., ; Lamy et al ., ; López et al ., ). Further studies are needed to investigate whether these patterns are generalizable across other plant families.…”

“…A recent meta‐analysis found that 33% of the variation in P 50 was contributed by differences within species (Anderegg, ). However, part of this variability could be a result of methodological aspects (Cochard et al ., ) and several individual studies have shown low plasticity in embolism resistance across climatically contrasted populations (Maherali & DeLucia, ; Martínez‐Vilalta et al ., ; Lamy et al ., , ; López et al ., ). The degree of coordination between leaf economics traits and hydraulic traits is also a leading research subject.…”

Does acclimation in cavitation resistance due to mechanical perturbation support the pit area or conduit reinforcement hypotheses in Phaseolus vulgaris?

“…Recently there has been greater appreciation for the importance of plasticity in hydraulic traits in response to various environmental factors (Anderegg , Badel et al , Fichot et al ). For example, cavitation resistance has been shown to shift in response to various environmental conditions including drought (Wortemann et al , Plavcová and Hacke , López et al ). Much of this work has been done using woody perennial species and there are still relatively few studies that have focused on plasticity in cavitation resistance and its importance in herbaceous annual plants.…”

“…In studying plasticity in xylem conduit size, conduit reinforcement and their impact on cavitation resistance, two environmental factors that might be particularly useful in altering stem structural traits are drought and mechanical perturbation. In response to reduced water, cavitation resistance has been shown to increase (Awad et al 2010, López et al ) and conduit size decrease (Holste et al , Plavcová and Hacke ) but the effect of drought on measures of reinforcement is less clear (Holste et al , Plavcová and Hacke , Awad et al 2010, López et al ). Mechanical perturbation can result in thicker stems and increased stem rigidity (Jaffe et al ) and these changes can be correlated with an increased production of strengthening tissues and a decrease in hydraulic conductivity (Smith and Ennos , Braam ).…”