Biology of dormancy and germination of Stellaria media (L.) Vill. and Stellaria nemorum L. seeds

Species of the genus Chickweed - Stellaria L. (Caryophyllacerae) currently attract researchers as sources of biologically active substances on the basis of which new herbal medicinal products of a wide range of action are being developed. Chickweed or S. media often serves as an object for assessing the resistance of ruderal plants to the used herbicides. The features of the latent period of species of this genus are not covered in scientific literature. The study of the peculiarities of biology and germination of weed seeds allows us to develop agrotechnical measures either to combat them or to develop technology for cultivating various food crops. The aim of this research was to study the latent period and the rhythms of seed germination of two Chickweed species: Stellaria media (L.) Vill. and S. nemorum L. The seeds collected in their natural habitats in Leningrad region, Vyborg district, in the vivinity of Olshaniki village (60°21'N, 29°44'E) in 2014-2017 were used. During studies, seeds with a total weight of 1-2 to 4-5 g were collected annually (each lot consisted of about 6-10 thousand seeds). Some seeds were stored in the laboratory (20-24°С), the other part in paper bags in the refrigerator at 5-7°С; their small lots were regularly germinated (See Table 1). To study seasonal rhythms of germination, 100 seeds from one lot were placed in triple replication in sterile Petri dishes on a filter paper which was moistened with distilled water as it dried. Germinated seeds were counted daily for 30 days. S. nemorum seeds were separated in fractions by size using soil sieves with a cell diameter of 1 mm (small) and 2 mm (large). Separation of S. media seeds was unsuccessful. Data are presented as arithmetic mean and error of the mean. It is shown that, annually, these species form full-fledged reproductive diaspores, which differ somewhat in their quality each year. Seeds of the first species (S. media) were germinated regardless of the season. The peak of germination occurred in spring. In summer and autumn, the germination rate did not exceed 20-25%. When stored in the laboratory, the viability of seeds persisted for 4 years. Seeds of the second species (S. nemorum) were germinated only in spring months; germination reached high values (See Table 2 and Fig.). Its seeds also retained their viability for a long time, with annual declines of 10-15%. S. media seeds began to germinate even in the refrigerator, at a temperature of+5°C. S. nemorum seeds only began to germinate at a temperature above +15°C. When stored in the laboratory, the germination of seeds of this species persisted for 4 years, decreasing by 10-15% every year. Seeds of the two studied species of the genus Stellaria demonstrated different life strategies. The annual S. media showed the preservation of germination for many years, and the perennial S. nemorum for 4 years. Consequently, the soil bank of seeds was different, the microbiotic species retained their germination capacity for less than 5 years, mesobiotics for more than 5 years, and macrobiotics formed a long-term seed bank. In annual and perennial species, the rhythms of germination were different: in annual species they were fixed outside the season and for perennial species only in spring (at the beginning of the growing season). The seeds of S. nemorum were of different quality. The paper contains 1 Figure, 2 Tables and 31 References.

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