期刊
PLANT CELL AND ENVIRONMENT
卷 29, 期 8, 页码 1618-1628出版社
WILEY
DOI: 10.1111/j.1365-3040.2006.01539.x
关键词
embolism; hydraulic resistivity; mechanical strength; plant water transport; wood density
Wood structure and function of juvenile wood from 18 conifer species from four conifer families (Araucariaceae, Cupressaceae, Pinaceae and Podocarpaceae) were examined for a trade-off between wood reinforcement and hydraulic efficiency. Wood density and tracheid 'thickness-to-span' ratio were used as anatomical proxies for mechanical properties. The thickness:span represented the ratio of tracheid double wall thickness to lumen diameter. Hydraulic resistivity (R) of tracheids on a cross-sectional area basis (R-CA) increased over 50-fold with increasing density and thickness:span, implying a strength versus efficiency conflict. The conflict arose because density and thickness:span were increased by narrowing tracheid diameter rather than by thickening walls, which may be developmentally difficult. In the Pinaceae and Cupressaceae species, density and thickness:span correlated strongly with protection from drought-induced embolism, suggesting that mechanical strength was required in part to withstand tracheid collapse by negative sap pressure. These species showed a corresponding trade-off between increasing R-CA and embolism protection. In contrast, species of Podocarpaceae and Araucariaceae were overbuilt for their embolism protection and were hydraulically inefficient, having greater density, thickness:span and R-CA, none of which were correlated with vulnerability to embolism.
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