Phenotypic plasticity and the leaf economics spectrum: plasticity is positively associated with specific leaf area

Phenotypic plasticity is a key mechanism by which plants respond to
changing or heterogeneous conditions. Efforts to predict phenotypic
plasticity across plant species have mainly focused on environmental
variability or abiotic conditions, i.e., site characteristics. However,
the considerable variation in phenotypic plasticity within sites calls for
alternative approaches. Different functional groups are thought to differ
in their plasticity levels. Further, traits such as leaf specific area
(SLA), leaf area (LA) and maximum photosynthetic rate (Amax) reflect
central aspects of plant strategies. Lower values of SLA, LA and Amax are
indicative of a resource-conservative strategy, which is thought to be
associated with lower phenotypic plasticity. We used meta-analytical data
to test whether plant functional group (herbs, woody deciduous and woody
evergreens) and SLA, LA and Amax are associated with phenotypic plasticity
in four trait types: biomass allocation, plant size, leaf morphology and
physiology. We obtained data from 168 plant species and accounted for
phylogenetic relationships in all analyses. We found a positive
relationship between SLA and phenotypic plasticity in biomass allocation,
leaf morphology and physiology, with differences across functional groups.
In contrast, there was no evidence of greater plasticity in plant size in
species with higher SLA; rather the opposite was true for woody
evergreens. Amax and LA showed similar, but less consistent associations
with phenotypic plasticity. Our results show the potential of building
predictive frameworks for phenotypic plasticity based on easily measured
plant functional characteristics. Results also provide insights into plant
strategies and suggest the existence of potential compromises:
resource-conservative, low-SLA species tend to be more stress-tolerant but
may be less able to cope with variable conditions due to their generally
lower phenotypic plasticity. Further studies are needed to explore the
mechanisms and the potential implications of this association.