Testing hypotheses that link wood anatomy to cavitation resistance and hydraulic conductivity in the genus Acer

Abstract

Summary• Vulnerability to cavitation and conductive efficiency depend on xylem anatomy. We tested a large range of structure-function hypotheses, some for the first time, within a single genus to minimize phylogenetic 'noise' and maximize detection of functionally relevant variation.• This integrative study combined in-depth anatomical observations using light, scanning and transmission electron microscopy of seven Acer taxa, and compared these observations with empirical measures of xylem hydraulics.• Our results reveal a 2 MPa range in species' mean cavitation pressure (MCP). MCP was strongly correlated with intervessel pit structure (membrane thickness and porosity, chamber depth), weakly correlated with pit number per vessel, and not related to pit area per vessel. At the tissue level, there was a strong correlation between MCP and mechanical strength parameters, and some of the first evidence is provided for the functional significance of vessel grouping and thickenings on inner vessel walls. In addition, a strong trade-off was observed between xylemspecific conductivity and MCP. Vessel length and intervessel wall characteristics were implicated in this safety-efficiency trade-off.• Cavitation resistance and hydraulic conductivity in Acer appear to be controlled by a very complex interaction between tissue, vessel network and pit characteristics.

Weak coordination among petiole, leaf, vein, and gas‐exchange traits across Australian angiosperm species and its possible implications

“…This is a particularly important shortcoming considering that pit and pit‐membrane ultrastructure varies widely across species, even within a single genus (Lens et al. 2011, 2013). However, our estimates of xylem‐specific conductance in petioles are correlated with measured xylem‐specific conductance in branches ( r 2  = 0.48; P  < 0.001) (Gleason et al.…”

Hydraulic properties and embolism in small-diameter roots of five temperate broad-leaved tree species with contrasting drought tolerance

“…In this species, the loss of root conductivity may have been compensated by the species' relatively large fine root biomass enabling Fraxinus to tolerate large leaf water potential amplitudes while maintaining constant sap flow rates even in dry summer periods (Köcher et al 2009). However, recent studies (e.g., Christman et al 2009;Lens et al 2011) produced evidence that the xylem vulnerability to cavitation may be more closely related to the inter-vessel pit structure than to vessel diameter. Already Zimmermann (1983) assumed that the vulnerability to cavitation caused by air-seeding is primarily dependent on the properties of the inter-vessel walls and their pits and the resulting capability of restricting the mass flow from one cell to another.…”

Embolism resistance as a key mechanism to understand adaptive plant strategies

“…Fine-scale interconduit pit adaptations regulate drought-induced embolism resistance Mechanical behaviour of pit quality characters Ultrastructural modifications of interconduit pits are good predictors to explain embolism resistance via air-seeding [18][19][20][21][22]. Within angiosperms, the huge variation in PM thickness (70-1900 nm) and maximum PM porosity (10-225 nm) show that species with thicker PMs have smaller PM pores and are better adapted to avoid air-seeding ( Figure 1c bottom [19]).…”

“…Thicker PMs are also presumed to be mechanically stronger, causing more resistance to stretching and preventing PM pores to become larger [18,24]. Likewise, narrower pit chambers [22,25] and vestured pits (Figure 1c middle [23]) prevent excessive PM deflection in some groups. The mechanical behaviour of pits and their PMs remains to be investigated thoroughly, and therefore also PM chemistry [26] needs special attention with reference to the pit type and developmental stage.…”