Esterase Polymorphism and Growth Form Differentiation in Poa Annua L.

SUMMARY Leaf esterase polymorphism in eight populations of Poa annua L., from two habitat types (four opportunist and four semi‐permanent populations), was demonstrated to be controlled by nine loci. Frequencies at five loci were studied. Locus Est 1 proved highly correlated with growth form: homozygotes AA were prostrate, whereas homozygotes BB were erect. All populations were polymorphic both for esterase isozymes and growth form. Mean frequencies of prostrate and erect plants were 12 and 88% respectively in opportunist populations, and 32 and 68% in semi‐permanent populations. The outcrossing rate was strongly dependent upon plant density, but in both types of habitat, prostrate and erect plants appeared to be able to exchange genes.