Kate is a plant physiologist interested in how plants respond to climatic extremes, with a focus on the plant water transport system (xylem). Kate also loves art and is passionate about science communication.
22
A trade-off
between growth rate and drought vulnerability within a drought-resistant tree species
Kate M. Johnson and Timothy J. Brodribb
Department of Biological Sciences, School of Natural Sciences, University
of Tasmania, Hobart 7001, Australia.
The
ideal plant water transport system is one that both is efficient, and resistant
to drought-induced damage (xylem cavitation), however, species rarely possess
both. This may be explained by trade-offs between traits, yet thus far, no
proposed trade-off has offered a universal explanation for the lack of both
highly drought-resistant and highly efficient water transport systems. Here we
find evidence for a new trade-off, between growth rate and resistance to
drought-induced xylem cavitation, in the canopies of Callitris rhomboidea. Wide variation in cavitation vulnerability was confined to
the branch tips (< 2mm in diameter), with very low variation in P50 in
larger diameter stems (> 2mm). We found a significant correlation between
cavitation vulnerability (P50) and distal branchlet internode length at the
branch tips in C. rhomboidea canopies. Branchlets with long internodes (8
mm or longer) were much more vulnerable to drought-induced xylem cavitation
than shorter internodes (4 mm or shorter). This suggests that varying growth
rates, leading to differences in internode length, drive differences in
drought vulnerability in C. rhomboidea trees. Understanding whether this trade-off
exists within and between species, will help us to uncover what drives and
limits plant drought resistance more broadly.