Integrative Xylem analysis of Chaparral Shrubs

Abstract

Chaparral shrub communities have been model systems for ecophysiological studies for more than 40 years, including examination of xylem in a range of contexts from mechanistic studies to ecological and evolutionary analyses. One of the advantages to studying chaparral shrubs is their clear environmental context, which places strong selection on xylem traits to tolerate drought and freeze/thaw stress. This chapter briefly reviews some of the main themes of studies that have sought to understand how xylem traits are adaptive in a Mediterranean-type climate. Chaparral species have been the focus of several important ecological xylem anatomy studies by Sherwin Carlquist and he has established clear links between certain anatomical traits and xylem safety, particularly as safety relates to the type of imperforate tracheary element in the background tissue of the xylem. In this chapter, some of these ideas were tested using a database of xylem safety and efficiency measures from 47 chaparral species. Carlquist’s ideas are evaluated and discussed in the context of current models of the factors that control the trade-off between xylem safety and efficiency.