In past decades plant functional trait and ecophysiology studies have identified consistent patterns of coordination among ecologically-important traits across plant species. It’s not clear yet whether such coordination hold true a) within populations, and b) have a genetic basis. Such knowledge not only can shed lights on the scale-dependency of trait coordination patterns, but is also necessary for breeding crop and tree varieties that balance potential trade-offs between productivity and stress resistance.
Here we present a series of studies examining the genetic variations in drought resistance and leaf economic spectrum traits in populations of two dominating species, lodgepole pine (Pl) and white spruce (Sw) in the boreal forests of Alberta, Canada, using field progeny trials and glasshouse experiments. We sampled gas exchange rates, foliar percent nitrogen (Nmass), lamina mass area ratio (LMA), and stable carbon isotope ratio (δ13C) from adults of 40 Pl and 32 Sw half-sib families grown in common gardens in the field. In the glasshouse experiments, we examined responses of gas exchange to repeated cycles of dry-down, and measured traits relevant for drought resistance, such as stomatal density and δ13C, in seedlings of subsets of the families sampled in the field.
Results/Conclusions
We found three key results from the field study. First, the Sw population showed significant genetic variation in sensitivity of stomatal conductance (gs) to vapor pressure deficit (VPD); the Pl population showed no significant genetic variation in stomatal sensitivity to VPD but in mean gs, which in turn, was negatively correlated with δ13C. Second, LMA and Nmass showed positive genetic correlations, and weaker (positive) phenotypic correlations in both species. Last, the Sw families with more sensitive stomata to VPD and higher δ13C values were originated from warmer, drier locations.
Preliminary analyses of the glasshouse experiments indicated that Pl families differed in the magnitudes of their responses of stomatal conductance to the drought treatment, and that declines in gas exchange rates became smaller in later dry-down cycles.
Based on the analyses done so far, we conclude that within our study populations, there were a) genetic variations in drought resistance traits, b) genetic correlations between traits known to be correlated across species, and c) variation in drought resistance traits along climate gradients.