PINYON (PINUS EDULIS, PINACEAE), ASSOCIATED WITH SOIL MOISTURE1

found here-allele 3 higher in frequency on dry sites-was consistent with previous studies of microgeographic variation in contrasting moist and dry sites. Trees within one of the dry sites were examined to test the hypothesis that stomata sizes and densities are heterogeneous among Gly genotypes. Heterozygotes had the longest and widest stomata; the stomatal area of heterozygotes was 28% greater than the stomatal area of homozygotes. Whereas the stomatal areas of the two homozygotes were similar, their shapes did not overlap when projected on a bivariate plot of length and width. These results suggest that stomatal shape may play a role in adapting pinyon to heterogeneity in soil moisture.

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