Rhythm of Seasonal Development and Minor Life Cycle of Prunella vulgaris L. (Lamiaceae) in Khakasia

Abstract

Seasonal rhythms of plant development are related to plant adaptation to surrounding ecological coenotic and climatic conditions. To discover the patterns of seasonal development of plants in different phytocoenoses, it is essential to observe individual shoots and the entire course of shoot formation. So far the data on the rhythm of seasonal development of Prunella vulgaris L., a plant of the circumboreal region, have been available for the European part of Russia only. We examined the rhythm of seasonal development and minor life cycle of Prunella vulgaris L., the long-rhizome life form, in Siberia (Khakasia) in 2012-2013. Observations were carried out in a forest meadow every 5-7 days in the spring-summer-autumn period and 1-2 times a month in the winter. The development of dicyclic meso-rosetted and winter monocyclic semi-rosetted generative monocarpic shoots was observed using the method by I.G. Serebryakov. It was determined that the differentiation of vegetative and generative spheres in Prunella vulgaris L. shoots in Siberia occurs in early spring within the year of flowering. The species forms spring and autumn leaf generations and phenologically can be described as a summer-winter green plant with a long growing season. The period of shoot development from its initiation to dying the above-ground parts lasts 26 and 14 months in dicyclic meso-rosetted shoots and winter monocyclic semi-rosetted shoots, respectively. In both cases the development of the primordial shoot inside the bud lasts 8 months while the duration of shoot development after emerging from the bud varies. The latter phase lasts 18 months in dicyclic meso-rosetted shoots and only 6 months in winter monocyclic semi-rosetted shoots. Start times and duration of phenological phases (budding, flowering, fruiting and dissemination) are related to the weather conditions in the habitats including fluctuations in air temperature, precipitation patterns and types