Phenotypic and developmental plasticity of xylem in hybrid poplar saplings subjected to experimental drought, nitrogen fertilization, and shading

Abstract

Variation in xylem structure and function has been extensively studied across different species with a wide taxonomic, geographical, and ecological coverage. In contrast, our understanding of how xylem of a single species can adjust to different growing condition remains limited. Here phenotypic and developmental plasticity in xylem traits of hybrid poplar (Populus trichocarpa×deltoides) was studied. Clonally propagated saplings were grown under experimental drought, nitrogen fertilization, and shade for >30 d. Xylem hydraulic and anatomical traits were subsequently examined in stem segments taken from two different vertical positions along the plant’s main axis. The experimental treatments affected growth and development and induced changes in xylem phenotype. Across all treatments, the amount of leaf area supported by stem segments (AL) scaled linearly with stem native hydraulic conductivity (K native), suggesting that the area of assimilating leaves is constrained by the xylem transport capacity. In turn, K native was mainly driven by the size of xylem cross-sectional area (AX). Moreover, the structural and functional properties of xylem varied significantly. Vulnerability to cavitation, measured as the xylem pressure inducing 50% loss of conductivity (P50), ranged from –1.71MPa to –0.15MPa in saplings subjected to drought and nitrogen fertilization, respectively. Across all treatments and stem segment positions, P50 was tightly correlated with wood density. In contrast, no relationship between P50 and xylem-specific conductivity (K S) was observed. The results of this study enhance our knowledge of plant hydraulic acclimation and provide insights into common trade-offs that exist in xylem structure and function.

Intraspecific trait variation can weaken interspecific trait correlations when assessing the whole‐plant economic spectrum

“…Trait expression and biomass allocation are known to differ among organs in response to light and nutrient availability (Farrior et al., 2013; Freschet, Swart, & Cornelissen, 2015). In our study, field‐grown juveniles exhibited lower LMA and higher WD, in agreement with other studies (Plavcová & Hacke, 2012; Russo & Kitajima, 2016). …”

“…The differences in LMA between glasshouse‐ and forest‐grown juveniles (Figure 5) are consistent with well‐known plastic responses to light availability (Givnish, 1988). The differences in WD we observed are also consistent with a recent analysis of xylem plasticity in response to shade (Plavcová & Hacke, 2012). If we were to interpret these results using a genetic explanation, then the seedlings in the field experiments would have had to have been consistently biased toward “low‐LMA” provenances, and the plants in the greenhouse experiments would have had to have been biased toward “high‐LMA” provenances.…”

Modelling the mechanical behaviour of pit membranes in bordered pits with respect to cavitation resistance in angiosperms

“…Data from the literature Anatomical and P 50 data were compiled from previous studies (Sperry and Hacke, 2004;Jansen et al, 2009;Plavcová et al, 2011;Lens et al, 2011;Plavcová and Hacke, 2012). We considered studies for which at least T m , D p and P 50 were measured.…”

Effect of Provenance and Climate on Xylem Anatomy of Haloxylon Ammodendron (C. A. Mey) Bunge in the Gurbantunggut Desert, China

“…The xylem responded to more arid conditions by increasing the dR and hR to improve water and starch storage. The xylem increased in both dV and wtV to account for both efficiency and safety in the xylem, which did not support the suggestion of a trade-off between efficiency and safety (Plavcová and Hacke, 2012;Hajek et al, 2016). The plants responded to the low temperature in January and strong winds from April to June by increasing wtF.…”