Fertility and Viability of Pollen Grains of <i>Taraxacum officinale</i> Wigg. s.l. (Asteraceae, Magnoliopsida) in the Gradient of an Anthropogenically Transformed Environment

Abstract

The fertility and viability of pollen grains of two morphological forms of Taraxacum officinale Wigg. s.l were estimated. These forms compose common coenopopulations growing in various coenotic and edaphic conditions. The studied forms have a developed gynoecia – a large number of fertile pollen grains capable of germination under certain temperature conditions. This points to the amphimictic properties of the plants. Comparison of data on the fraction of fertile pollen grains and seed productivity allows one to assume that some seeds develop without going through fertilization. This can be treated as evidence of the apomictic properties of the plants. Therefore, the presence of optional apomixis in the species in question was indirectly confirmed in the course of our work. The fertility of pollen grains was shown to be a more ecology-dependent property of the male gametophyte than its viability. In the favorable conditions the part of fertile pollen grains in f. dahlstedtii and f. pectinatiforme differs insignificantly. Under stress conditions, the differences between the forms of the dandelion by this indicator amplify. This can be considered as a mechanism of adaptation to adverse environmental factors. The revealed differentiation of the morphological forms of the dandelion by the indicator of the fertility of pollen grains enables one to assume that edaphic and coenotic stresses lead to an increase in the differences between them by the degree of apomictic and amphimictic properties. The morphological forms of the dandelion, realizing two reproductive strategies under stress conditions, support both the quantity and genetic heterogeneity of the coenopopulations. The morphological forms studied do not differ in the proportion of viable pollen grains. This indicator rises to a certain extent only in the gradient of coenotic competition. This can be considered as a manifestation of the properties of optional apomict.