Responses of Gramineae and legume germination to temperature and light

Grasses and legumes are the main producers in grassland ecosystems, and seed germination and seedling growth are major aspects of plant life history. Therefore, exploring the response characteristics of seed germination of gramineous plants to environmental factors such as temperature and light is an important basis for the establishment of artificial grassland and degraded grassland dominated by gramineous plants. Two graminaceous forages (Agropyron cristatum and Paspalum notatum) and four leguminous forages (Medicago sativa ‘Gongnong No.1’, M. sativa ‘Algonquin’, Astragalus adsurgens and Vicia villosa) were selected to compare seed germination characteristics at five constant thermal treatments (30, 25, 20, 15, and 10 ℃) and five alternative temperatures (15 ℃/6 ℃, 25 ℃/15 ℃, 20 ℃/30 ℃, 20 ℃/10 ℃, and 30 ℃/15 ℃). This was accompanied by two light regimes, 12 h light/12 h dark and 24 h dark. The results revealed significant differences among species. Germination percentage, days to first germination, and germination index varied substantially among species. Under constant temperatures, the germination percentage of gramineous forages was relatively low (< 55.00%) and the germination percentage of leguminous forages was higher (> 56.00%). The seed germination of gramineous forages started later (> 6 d), and the seed germination of leguminous forages started earlier than that of gramineous forages by 1～2 d. The germination index of gramineous forages was lower than that of legumes, among which M. sativa ‘Gongnong No.1’ had the highest germination index and the strongest seed vitality. The germination percentage of A. cristatum in total darkness was higher than that in light–dark alternating conditions. Total darkness inhibited the germination of M. sativa ‘Gongnong No.1’, M. sativa ‘Algonquin’, and A. adsurgens. The range of germination for V. villosa under constant and variable temperature conditions was 84.00%～99.00%, with a wide range of seed germination temperatures. This study, which examines the seed germination characteristics of typical grasses under different temperatures and light conditions, can provide a reference for the establishment of grass and legume mixed artificial grassland and the supplementary sowing and restoration of degraded grassland.