Linking xylem water storage with anatomical parameters in five temperate tree species

Abstract

The release of water from storage compartments to the transpiration stream is an important functional mechanism that provides the buffering of sudden fluctuations in water potential. The ability of tissues to release water per change in water potential, referred to as hydraulic capacitance, is assumed to be associated with the anatomy of storage tissues. However, information about how specific anatomical parameters determine capacitance is limited. In this study, we measured sapwood capacitance (C) in terminal branches and roots of five temperate tree species (Fagus sylvatica L., Picea abies L., Quercus robur L., Robinia pseudoacacia L., Tilia cordata Mill.). Capacitance was calculated separately for water released mainly from capillary (CI; open vessels, tracheids, fibres, intercellular spaces and cracks) and elastic storage compartments (CII; living parenchyma cells), corresponding to two distinct phases of the moisture release curve. We found that C was generally higher in roots than branches, with CI being 3-11 times higher than CII Sapwood density and the ratio of dead to living xylem cells were most closely correlated with C In addition, the magnitude of CI was strongly correlated with fibre/tracheid lumen area, whereas CII was highly dependent on the thickness of axial parenchyma cell walls. Our results indicate that water released from capillary compartments predominates over water released from elastic storage in both branches and roots, suggesting the limited importance of parenchyma cells for water storage in juvenile xylem of temperate tree species. Contrary to intact organs, water released from open conduits in our small wood samples significantly increased CI at relatively high water potentials. Linking anatomical parameters with the hydraulic capacitance of a tissue contributes to a better understanding of water release mechanisms and their implications for plant hydraulics.

Wood allocation trade‐offs between fiber wall, fiber lumen, and axial parenchyma drive drought resistance in neotropical trees

“…The ecological importance of capacitance from parenchyma tissue in neotropical trees remains unresolved. The separation of capacitance into “fast” and “slow” capacitance from moisture release curves in tropical species could provide more insight into the role of parenchyma tissue in driving stem water storage (Jupa et al, ).…”

Coordination and trade‐offs between leaf and stem hydraulic traits and stomatal regulation along a spectrum of isohydry to anisohydry

“…Consistent with this, hydroscape area was positively correlated with wood density. The dependence of hydroscape area on wood density appears to be mediated largely by the negative impact of increasing wood density on stem capacitance (Jupa et al, ; McCulloh, Johnson, Meinzer, & Woodruff, ; Scholz et al, ) via the effects of wood density on the relative abundance of xylem cell types such as parenchyma, fibres, and vessels (Figure ; Jupa et al, ). Moreover, an earlier study of 61 species showed that species with higher wood density (lower C) had a higher proportion of axial parenchyma area but lower proportion of ray parenchyma (Martínez‐Cabrera, Jones, Espino, & Schenk, ), suggesting that stem capacitance is negatively related to the axial parenchyma fraction, but positively related to the ray parenchyma fraction, which is partially consistent with our findings.…”

“…Fractions and dimensions of xylem cell types were measured because these traits were reported to be associated with stem capacitance (Jupa, Plavcová, Gloser, & Jansen, 2016). Stem segments up to a maximum diameter of 0.8 cm were obtained from six different individuals of each species.…”

Radial variation of wood functional traits reflect size‐related adaptations of tree mechanics and hydraulics

“…In angiosperms, fibres serve primarily for material strength; vessels transport water axially; and living parenchyma cells, in axial as well as radial alignment, store organic compounds such as carbohydrates, are actively defending against pathogens and are important for refilling embolised conduits (Brodersen & McElrone, 2013;Morris et al, 2016). Both living and dead cells can also store water, although the contribution to wood water capacitance, measured as the change in the water volume fraction per change in tissue water potential, was lower than that of apoplastic water (in fibres, vessels and intercellular spaces) in five temperate species (Jupa, Plavcová, Gloser, & Jansen, 2016). In addition to different cell types, there is substantial variation in the size, form, arrangement and frequency of these (Lachenbruch & McCulloh, 2014;Ziemińska, Westoby, & Wright, 2015).…”