Adaptedness of Variants at an Alcohol Dehydrogenase Locus in Bromus mollis L. (Soft Bromegrass)

Abstract

Alcohol dehydrogenase [ADH, EC 1.1.1.1] is highly polymorphic in many plant and animal species. Evidence is given that the naturally occurring, electrophoretically detectable allozyme variants of the Adh1B locus in B. mollis can respond differentially to environmental stresses. ADH activity may be specifically involved in response to these stresses. Crude extracts of predominantly selfed seeds sampled from plants of known Adh1B genotype were assayed for their ADH activity in forward and backward reactions. Seeds from .**GRAPHIC**. plants produced extracts about 12% less active in both directions than seeds from their .**GRAPHIC**. counterparts. Such .**GRAPHIC**. plants produced about 13% more dry matter when grown under continuous flooding in the greenhouse. No difference between genotypes was detected in control pots. Seeds of .**GRAPHIC**. plants showed an advantage over the alternative homozygotes in more rapid germination at 2.degree. C, but no difference was found at 15.degree. C. The variants are differentially adapted, and this is likely to play a role in the maintenance of the polymorphism in natural populations.