Abstract:
Given the fundamental importance of xylem
safety and efficiency for plant survival and fitness, it is not
surprising that these are among the most commonly studied
features of hydraulic architecture. However, much remains
to be learned about the nature and universality of conflicts
between hydraulic safety and efficiency. Although selection
for suites of hydraulic traits that confer adequate plant
fitness under given conditions is likely to occur at the
organismal level, most studies of hydraulic architecture
have been confined to scales smaller than the whole plant,
such as small-diameter branches and roots. Here we discuss
the impact of the spatial and temporal contexts in which
hydraulic traits are studied on the interpretation of their
role in maintaining plant hydraulic function. We argue that
further advances in understanding the ecological implications
of different suites of plant hydraulic traits will be
enhanced by adopting an integrated approach that considers
variation in hydraulic traits throughout the entire plant,
dynamic behavior of water transport, xylem tension and
water transport efficiency in intact plants, alternate mechanisms
that modulate hydraulic safety and efficiency, and
alternate measures of hydraulic safety and safety margins.
