Morphology and germination characteristics of seeds with underdeveloped embryo

Botanical Garden-Institute FEB RAS, Vladivostok, Russia

Species with an undeveloped embryo account for ca. 18–20 % of the flora of the Far East. Embryo formation in seed at the maternal plant can stop at different embryogenesis stages. The embryo remains small in comparison with endosperm and mature seeds don’t germinate. Seeds of 15 herbaceous spring-blooming species from 5 plant families were studied. Seed linear dimensions varied greatly between the species. Caltha silvestris (2.2 x 1.1 mm) and Hylomecon vernalis (2.4 x 1.6 mm) have the smallest seeds. Adonis amurensis (3.6 x 2.5 mm) has somewhat larger seeds and the largest seeds were observed in Arsenjevia glabrata (7.1 x 4.7 mm). Embryo lengths and its development stages are speciesspecific. In mature seeds of Enemion raddeanum and Ranunculus franchetii embryo is pyriform 0.1–0.2 mm long. In cordate embryos of Adonis amurensis and Hylomecon vernalis the primordial cotyledon is clearly visible. The embryo length is 0.2–0.3 mm. Embryo of Anemonoides reflexa is 0.3–0.4 mm long, cotyledons compose ca. 30 % of its length. In hypocotyl and cotyledon vascular bundles are evident. After seed dissemination, the embryos are developing during summer and autumn. Postembryonic embryo development lasts from 40–55 days in Hepatica asiatica and Asarum sieboldii to 110–120 days in Epimedium macrosepalum and Eranthis stellata. It was found that seeds of Anemonoides reflexa, Gagea nakaiana and Lloydia triflora need morphological endogenic dormancy and have summer or autumn germination. Seeds of Arsenjevia rossii, Plagiorhegma dubia and Caltha silvestris having morpho-physiological type of endogenic dormancy germinate next spring after natural stratification by low winter temperatures. It was revealed that most species produce recalcitrant seeds containing 50–70 % of moisture necessary for embryo's development. After 2–3 months storage seeds lose germination ability.

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