Features of Seed Reproduction of Saposhnikovia divaricata (Apiaceae)

Abstract—Saposhnikovia divaricata (Turcz. ex Ledeb.) Schischk. (Apiaceae) is a useful medicinal plant, which contain a number of substances with a wide range of pharmacological activity; chromones, in particular, are found in the roots. For this reason, plants are heavily harvested from the wild, resulting in the population low density. S. divaricata is a taproot perennial monocarpic that reproduces by seeds only. The introduction of the species, the study of seed productivity and seed reproduction is a vital task for the development of industrial plant cultivation and the restoration of natural populations. The purpose of this work is to study seed production and biology of seed propagation. The generative shoot of S. divaricata is a synflorescence (a panicle of double umbels) with a floral unit being a double umbel. Plants from natural habitat and cultivated ones were studied. A comparative analysis of the seed production of double umbels, depending on their position on the rachis was carried out. The proportion of seed set (seed number/ovule number) and fruit set (fruit number/flower number) in a simple umbel, the potential and real seed productivity of a simple umbel, double umbel, and an individual plant were determined. Fruit of S. divaricata is a cremocarp consisting of two single-seeded mericarps. The seeds have a thin spermoderm, so they were stored and germinated with the pericarp. Seeds (mericarps) for germination were collected from natural populations and cultivated plants considering their position on the rachis, and stored for eight months under laboratory conditions (+23–25 °C). The results of the experiment included data on the duration of the period from the beginning of the experiment to the seed germination, the duration of the germination period (from the beginning of germination), laboratory germination of seeds (%), germination energy (%), rate of germination energy (%). All cultivated plants were monocarpic. The diameter of the synflorescence reaches 124 cm; on average, about 70 double umbels with fruits are formed on it. It was found that in introduced plants, seeds from the branches of the third order make up more than 50% of the real seed production, and from the second and fourth order branches – 21 and 26%, respectively. In natural populations, seeds from the fourth order branches account for 45% of the real seed production, of the third – 30%, of the 2nd – 15%. In the introduced plants, the real seed production of the second generation was about 6000 seeds per individual, which is higher than that of plants in natural populations, where the seed set is 65%. The seeds exhibit non-deep dormancy, and the period before germination does not exceed 10 days. Seed germination is dynamic; more than 50% of the germinated seeds have sprouted within seven days. Laboratory germination was higher in the seeds from the natural population, than from the introduced plants. The highest laboratory germination in introduced plants was found in seeds from double umbels of the second or third order branches – 72–73%, and from the natural populations – in seeds from the shoots of the third or fourth order branches – more than 90%.