Ontogenesis and age structure characteristics of Dasystephana macrophylla (Pallas) Zuev populations in the Altai Mountains

Dasystephana macrophylla (Pallas) Zuev is one of the species of the gentian familv (Gentianaceae). D. macrophylla is a summergreen herbaceous taprooted monopodiallv growing polvcarpic with rosellate lodging shoot which belongs to mesophvtes. We conducted observations in 2015-2016 and determined a plot of motefy-grass meadow in the northern part of the SeminskiY Ridge between Shebalino village and Kumafyr village (51°17' N, 85°40' E) for studving. D. macrophylla is more abundant and has good development compared with other populations of steppes and wood meadow larch forests of the Central Altai. D. macrophylla population is located in the north-west gentle slope of the steppe meadow. The soil is chernozem-like. The upper part of the slope is limited bv a park-like motelv-grass larch forest; the lower part is bv a willow birch forb forest along the banks of the Sema river. The average height of the grass stand in 2016 was 35 cm, which is far greater than in dry 2015. The projective coverage was 95%. In order to assess the intensitv of self-renewal of the population, we calculated the indices of generativitv, aging and general age according to IN Kovalenko (2016). The variabilitv of the ontogenetic spectrum of the coenopopulation was estimated using the age index (A) according to AA Uranov (1975). We determined the efficiencv index (ю) according to LA Zhivotovskiv (2001). The ontogenetic states were described, based on the classification of TA Rabotnov (1950) which was later completed bv AA Uranov. We found all age states of D. macrophylla from seeds and sprouts to senile individuals in the examined population (See Fig. 1). Four periods and ten ontogenetic states were detected in the population (See Fig. 2). Reproduction is accomplished onlv bv seeds. Seeds are brown, shinv, exalate, and vety small - 0.5-1 mm. Four age states were identified in the pre-regenerative period. The main features of an adult plant are manifested in the virgin condition. The leaves are lanceolate with 5 veins (the length of the leaf blade is 19-23 cm, the width is 1.7-3.4 cm). The rhizome is 0.7-1.2 cm in diameter, the number of secondarv roots increases. The main root is preserved. Its particulation starts from the bottom, thus forming 4-6 cord-like areas. In the generative period three age-related states were identified. The rosellate shoot of voung generative plants reaches 6-10 cm in height, with 5 pairs of basal leaves. Most of the leaves are concentrated at the base of the stem and one generative shoot with 2-9 flowers collected in 1-3 whorls. A middle-aged generative plant is characterized bv the greatest capacit}^ An old generative plant is characterized bv a decrease in the size. The base of the stem is surrounded by a multitude of old leaves. We distinguished two age conditions in the post-generative period: subsenile (plants are similar to juvenile with only one difference in the rhizome which is deteriorating) and senile (plants have weak shoots with 2-4 leaves; the rhizome is dark and deteriorated). According to the "delta-omega" classification, D. macrophylla population is considered young since its indices are the following: A < 0.35 and ю < 0.60 (See Table). The index of aging is quite low which points out that the population is young. High renewability index values demonstrate that the population is well reproducing. Most individuals of D. macrophylla population are in the generative age state with a rather high generative index. The paper contains 2 Figures, 1 Table and 24 References.

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