The hydraulic architecture of Populus

Abstract

Populus species are among the fastest-growing temperate trees. Poplar and aspen genotypes are used as a source of fiber, fuel, and shelter. Populus has not only been used as a model for studying wood development, but is also emerging as a model plant for studying xylem and aquaporin function. This chapter discusses general characteristics of poplar xylem. Recent findings on transport efficiency, vulnerability to embolism formation, and phenotypic plasticity are synthesized. The data indicates that growing conditions can have a strong effect on vessel diameters, transport efficiency, and cavitation resistance. In boreal environments, narrow vessels may be advantageous for sustained tree growth. Trembling aspen (Populus tremuloides) has recently shown widespread die-off across many parts of western North America, and mortality has been linked with hydraulic failure of roots and branches. Poplar species and their hybrids vary tremendously in their stomatal sensitivity to water deficits. Even within a species, stomatal behavior may vary depending on the site and growing conditions. Radial exchange of water between phloem, cambium, xylem, and pith is likely facilitated by aquaporins. These water channels could impact various processes including root water uptake and wood development.