Leaf economics traits in wine grapes

Resource acquisitive plant species are expected to show stronger trait
integration vs. resource conservative species, due to simultaneous
selection for multiple resource requirements including light, water, and
nutrients. While this hypothesis has been invoked to predict interspecific
differences in trait variation and integration, it has not been tested to
explain intraspecific trait variation (ITV) and trait integration among
varieties of crop species. We quantified nine leaf physiological,
water-use, chemical, and morphological traits related to acquisition and
use of light, CO2, water, and nutrients, across six varieties of wine
grapes (Vitis vinifera L.), in order to quantify the extent of ITV and
trait integration among one of the world’s most common and economically
important perennial crops. This dataset was also used to test the
hypothesis that within a crop species, resource acquisitive varieties
express stronger trait integration vs. resource conservative varieties.
All leaf traits varied significantly across wine grape varieties, and
formed an intraspecific resource acquisitive-resource conservative axis of
variation within wine grapes. Consistent with hypotheses on trait
variation and integration, wine grape varieties expressing resource
acquisitive trait syndromes were associated with stronger trait
integration vs. those expressing resource conservative trait syndromes.
Specifically, varieties expressing greater values of light-saturated
photosynthesis (Asat), stomatal conductance (gs), maximum carboxylation
(Vcmax) and electron transport (Jmax) rates, leaf nitrogen concentrations,
and leaf area, expressed a ~45-65% increase in the number of significant
bivariate trait correlations compared to resource conservative varieties.
However, within all varieties we detected strong and consistent
integration among leaf physiological traits, indicating a mechanistic
physiological basis that governs an intraspecific Leaf Economics Spectrum
in wine grapes. Strong trait integration in resource acquisitive wine
grape varieties, support the hypothesis that “fast trait” plants have
simultaneously been selected to optimize multiple rates of resource
uptake, through multiple suites of traits. Our work clarifies the
mechanisms by which resource acquisitive species, particularly crops, are
able to capture multiple limiting resources to enhance their growth
performance. This study also addresses a gap in our knowledge regarding
the magnitude of intraspecific variation in trait integration.