Functional relationships between wood structure and vulnerability to xylem cavitation in races of Eucalyptus globulus differing in wood density

Abstract

Wood density can be considered as a measure of the internal wood structure, and it is usually used as a proxy measure of other mechanical and functional traits. Eucalyptus is one of the most important commercial forestry genera worldwide, but the relationship between wood density and vulnerability to cavitation in this genus has been little studied. The analysis is hampered by, among other things, its anatomical complexity, so it becomes necessary to address more complex techniques and analyses to elucidate the way in which the different anatomical elements are functionally integrated. In this study, vulnerability to cavitation in two races of Eucalyptus globulus Labill. with different wood density was evaluated through Path analysis, a multivariate method that allows evaluation of descriptive models of causal relationship between variables. A model relating anatomical variables with wood properties and functional parameters was proposed and tested. We found significant differences in wood basic density and vulnerability to cavitation between races. The main exogenous variables predicting vulnerability to cavitation were vessel hydraulic diameter and fibre wall fraction. Fibre wall fraction showed a direct impact on wood basic density and the slope of vulnerability curve, and an indirect and negative effect over the pressure imposing 50% of conductivity loss (P50) through them. Hydraulic diameter showed a direct negative effect on P50, but an indirect and positive influence over this variable through wood density on one hand, and through maximum hydraulic conductivity (ks max) and slope on the other. Our results highlight the complexity of the relationship between xylem efficiency and safety in species with solitary vessels such as Eucalyptus spp., with no evident compromise at the intraspecific level.

Fight or flight? Potential tradeoffs between drought defense and reproduction in conifers

“…Relationships among growth, xylem anatomy, and hydraulic safety are well established (Sperry et al 2003, Xu et al 2014, Venturas et al 2017, Barotto et al 2018. Hydraulic failurebreakage of the water column within xylem -can occur when air embolism blocks water flow (Sperry et al 1988, Cochard 2006, Barotto et al 2018, or when water potentials within the xylem become too negative and the xylem cell implodes (Hacke et al 2001, Pittermann et al 2006b). Drought increases the likelihood of either of these mechanisms of hydraulic failure by decreasing water potentials within the soil and increasing the tension applied to the water column along the soil-plant-atmosphere continuum (Hacke et al 2000.…”

“…We first review current understanding of C allocation to growth, tradeoffs between growth and hydraulic safety, and how drought modifies these allocation patterns. Tradeoffs between growth and hydraulic safety are well studied (Xu et al 2014, Venturas et al 2017, Barotto et al 2018, but often only with respect to tree growth and survival. Here we place these tradeoffs into a fitness context by reviewing the C budget implications of growth, hydraulic safety, and the interaction of the two for reproductive capacity.…”

Wood Architecture and Composition Are Deeply Remodeled in Frost Sensitive Eucalyptus Overexpressing CBF/DREB1 Transcription Factors

“…Beyond the vascular traits, the fiber characteristics of the CBF-OE lines may positively influence survival under adverse environmental conditions. The overall increase in cell wall surface as well as the increased lignin content supported by induction of expression of lignin biosynthesis genes as observed in the xylem of CBF-overexpressors, may also positively impact cavitation resistance as shown in different species including Eucalyptus [44,45]. More generally, these traits likely participate in strengthening the cell walls to prevent freezing damage or cell collapse as reported for cold-hardened plants [46].…”

Drought tolerance ofHakeaspecies (Proteaceae) from a range of biomes and life-histories predicted by climatic niche

“…P 50 is known to be correlated with life history (Pratt et al, 2007), structure and function (Brodribb and Holbrook, 2004;Jacobsen et al, 2007), and species climate range (Bourne et al, 2017). For instance, in drier climates species tend to have higher wood density, which provides greater resistance to xylem conduit implosion under high xylem tensions and is strongly correlated with P 50 (Barotto et al, 2018;Hacke et al, 2001;Jacobsen et al, 2005).…”