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Seed dormancy in rare plant species with underdeveloped embryo//Покой семян у редких видов растений, характеризующихся недоразвитием зародыша

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Elena Valentinovna Andronova
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Keywords : 1 2 1 04.12.2019; Revised: 15.12.2019; Accepted and Published online: 20.12.2019 The analysis of data on fruitаge, heterospermy, viability of seeds and seed progeny in Orchis purpurea at the northeastern limit of distribution (Krasnodar region and Crimea) was carried out. The percentage of fruit formation in the Krasnodar region was low with natural pollination (on average 1-4 %), and higher with artificial pollination (on average 34-77%). In the Crimea the percentage of fruit set varied from 9 % (forest) to 39 % (meadow). Seeds were differed in vitality; color of seed coat and embryo, as well as by the degree of homogeneity of their dimensional parameters (length, width) and shape. Plants from the populations of the Krasnodar region were characterized by a high number of non-viable seeds, without embryo or with degenerating embryo. It was shown that the proportion of seeds without embryos in fruits obtained by autogamy or geitonogamy is higher (between different plants 22-93 %, in average 63 %) than in fruits formed after cross-pollination between different individuals (xenogamy) (3-69 %, in average 34 %). It was found that a high proportion of non-viable seeds are a consequence of the manifestation of lethal anomalies of embryogenesis. The viability of the seeds (both from the Caucasus and Crimea) in a germination test was low. Plants from the studied populations are characterized by low real seed productivity. Based on the results of the cytoembryological study, a general conclusion can be drawn that the low real seed productivity of O. purpurea, both in the Caucasus and in the Crimea, arises due to the lethal anomalies manifested both at the stage of seed development and in the post-seed period.
Oksana G Butuzova
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In the conditions of temperate climate, a certain reproductive strategies were developed in plants. Seed dormancy and connected with it the phenomenon of embryo postdevelopment after dissemination are considered to be one of these strategies. This phenomenon is noted in plants from various climatic zones, differing in life cycles and types of dormancy (morphological, morpho-phisiological). It is permissible to suppose that the more complex and prolonging the processes of seed formation and overcoming dormancy, the greater variability is manifested in them. A comparative study of seed formation in two contrasting species of the family Ranunculaceae – a forest Pulsatilla vulgaris Mill. and mountain Helleborus niger L. was carried out. Both species are ephemeroids, but the process of seed maturation and postdeveloping in H. niger is several times longer than in P. vulgaris, whereas the degree of embryo differentiation at dissemination is, on the contrary, lower (heart-shaped stage in hellebore, early torpedo in the lumbago). This affects the peculiarities of reproductive structures development and their functioning, primarily, on the accumulation and consumption of nutrients. The following features were revealed in H. niger: photosynthetic elements of the perianth, heterospermy, earlier accumulation of nutrients in the endosperm, specific fan-shaped zonality in the rows of its cells, ephemeral functioning of the antipodes, clear boundaries of the endosperm cavity without signs of cell lysis, that is probably associated with switching of transport pathways (through the micropyle before the dissemination and directly from the endosperm cells in the postdevelopment) and economical consumption of substances throughout all embryogenesis. The peculiarities of P. vulgaris include the presence of pericarp with numerous starch grains, longer functioning of antipodes performing a storage function, lysis of endosperm cells adjacent to the endosperm cavity, that enables the more rapid development of the embryo. It was also suggested that, along with the archaic and conservative nature of the phenomenon of embryo underdevelopment in seeds, it probably acquired sufficient plasticity in evolution.
Elena Valentinovna Andronova
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Cardiocrinum cordatum (Thunb.) Makino var. glehnii (F. Schmidt) Hara (Liliaceae) a rare species is characterized by an underdeveloped embryo during dissemination and by the difficulty of seed germination. The aim of the work was to clarify the type of seed dormancy and optimization of seed reproduction in this species by combining various methods: germinating of seeds at different temperature regimes and the culture of isolated embryos in vitro in light and darkness. It was proved that C. cordatum var. glehnii has both the physiological inhibition of embryo postdevelopment as well as seed germination. It was found to be overcome under the influence of two factors: temperature and illumination. Physiological mechanism of inhibition of seed germination was removed only after prolonged exposure at low positive temperature (0-3°C). The results of the study allowed to solve finally the problem of the type of seed dormancy in C. cordatum var. glehnii and classify it as a deep complex morphophysiological one.