Dynamics of leaf water relations components in co‐occurring iso‐ and anisohydric conifer species

Abstract

Because iso- and anisohydric species differ in stomatal regulation of the rate and magnitude of fluctuations in shoot water potential, they may be expected to show differences in the plasticity of their shoot water relations components, but explicit comparisons of this nature have rarely been made. We subjected excised shoots of co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis to pressure-volume analysis with and without prior artificial rehydration. In J. monosperma, the shoot water potential at turgor loss (Ψ(TLP)) ranged from -3.4 MPa in artificially rehydrated shoots to -6.6 MPa in shoots with an initial Ψ of -5.5 MPa, whereas in P. edulis mean Ψ(TLP) remained at ∼ -3.0 MPa over a range of initial Ψ from -0.1 to -2.3 MPa. The shoot osmotic potential at full turgor and the bulk modulus of elasticity also declined sharply with shoot Ψ in J. monosperma, but not in P. edulis. The contrasting behaviour of J. monosperma and P. edulis reflects differences in their capacity for homeostatic regulation of turgor that may be representative of aniso- and isohydric species in general, and may also be associated with the greater capacity of J. monosperma to withstand severe drought.

Climatic limits of temperate rainforest tree species are explained by xylem embolism resistance among angiosperms but not among conifers

“…However, our conclusion that these traits are independent is based on interspecific differences in average trait values. Intraspecific variation in both of these traits was relatively low in our study, but other studies have demonstrated notable intraspecific variation in stem P50 (Love et al , ) and osmotic adjustments to leaf TLP (Meinzer et al , ; Maréchaux et al , ; Nolan et al , ; Johnson et al , ). Future tests of this relationship should account for both interspecific differences and intraspecific variation to gain a multiscale perspective on the strength of integration between stem P50 and leaf TLP.…”

Comparative Drought Responses of Quercus ilex L. and Pinus sylvestris L. in a Montane Forest Undergoing a Vegetation Shift

“…The anisohydric behavior of Q. ilex observed here is at odds with the general view considering this species as isohydric [27], even in studies conducted in a nearby valley in the same study area [33,47]. Importantly, the iso-/anisohydric dichotomy does not account for differences in vulnerability to xylem embolism [12], nor for leaf traits involved in turgor regulation [65]. Given the current methodological controversy on the measurement of vulnerability to xylem embolism (e.g., [48,61]) we cannot be sure that the extremely high PLC values estimated here are real.…”

Contrasting strategies of hydraulic control in two codominant temperate tree species

“…Species with deeper roots can access water at greater depths than are unavailable to more shallowly rooted species (Jackson et al, ; Canadell et al, ). Different species exhibit a spectrum of traits that vary in cavitation risk across all three of these axes of hydraulic control (Figure ; Meinzer, Woodruff, Marias, McCulloh, & Sevanto, ).…”