Adaptive variation and plasticity in nonstructural carbohydrate storage
in a temperate tree species
Abstract
Trees’ total amount of nonstructural carbohydrate (NSC) stores and the
proportion of these stores residing as insoluble starch are vital traits
for individuals living in variable environments. However, our
understanding of how stores vary in response to environmental stress is
poorly understood as the genetic component of storage is rarely
accounted for in studies. Here, we quantified variation in NSC traits in
branch samples taken from over 600 clonally transplanted black
cottonwood (Populus trichocarpa) trees grown in two common gardens. We
found heritable variation in both total NSC stores and the proportion of
stores in starch (H2TNC = 0.19, H2PropStarch = 0.31), indicating a
substantial genetic component of variation. In addition, we found high
amounts of plasticity in both traits in response to cold temperatures
and significant genotype-by-environment (GxE) interactions in the total
amount of NSC stored (54% of P is GxE). This finding of high GxE
indicates extensive variation across trees in their response to
environment, which may explain why previous studies of carbohydrate
stores’ responses to stress have failed to converge on a consistent
pattern. Overall, we found high amounts of environmental and genetic
variation in NSC storage concentrations, which may bolster species
against future climate change.