Sexual and ontogenetic structures of gynodioecious Geranium pseudosibiricum J. Mayer (Geraniaceae) in Altai Mountains

Abstract

Geranium pseudosibiricum J. Mayer. is a gynodioecious North and Central Asian species. The study was conducted in a grass meadow on the edge of larch forest in the Altai Republic. The aim was to study the sexual and ontogenetic structures of the coenopopulation of G. pseudosibiricum. The generative individual consists of shoots of only one sexual form: hermaphrodite with bisexual flowers and female with pistillate flowers. There are significant differences in the length of corolla: the length of bisexual flowers is 12.2 ± 0.29 mm, pistillate flowers 6.7 ± 0.19 mm. The bisexual flower has well-developed stamens and anthers; the pistillate flower has stamens with underdeveloped anthers. There are no significant differences between hermaphrodite and female individuals in the number of generative shoots and the number of flowers per individual. The ontogenetic structure of the coenopopulation of G. pseudosibiricum is dominated by pregenerative individuals − 53%. Good seed germination contributes to maintenance of sexual structure of the coenopopulation. The female frequency is 55% of the total number of generative plants. The detected morphological differences between bisexual and pistillate flowers and the high female frequency may indicate a high degree of sexual differentiation of G. pseudosibiricum.