Seed Germination Of Four Vicia Species Grown In Alpine Grassland Responses To Temperature And Water

The temperature and water are important environmental factors affecting seed germination. This study investigated the responses of seed germination to different temperatures and water potentials of four Vicia species which grown in alpine grassland of Gansu China by means of.the thermal model and hydrotime model. The species included3wild species of Vicia angustifolia, V. amoena and V. unijuga and1cultivated species of V. sativa Var Lanjian No3. The main results obtained were summarized as following:1) The base temperature (Tb) and the optimum temperature (T0) were almost the same among the results calculated basing on different germination rates (1/tg, g=20%-80%)for each of the4species. However, except of V. sativa Var Lanjian No3, the ceiling temperatures (Tc) were.varied at different germination rates in other3species.2) The germination threshold values and the themal constant (θT) were varied among the4species. The values calculated basing on the T50indicated that the Tb was0.43℃,3.29℃,2.44℃and-0.48℃, the To was19.64,19.84.20.09and16.05, and the Tc was30.53,37.17,37.37and31.66℃, while the9T was32.8℃.d,38.2℃.d,40.2℃.d and38.1℃.d for Vicia angustifolia, V. amoena, V. unijuga and V. sativa, respectively.3) The lowest water potential (Ψb) and the hydrotime constant (θH) were different among the species. The Ψb was-1.29MPa,-1.3MPa,-1.29MPa and-1.36MPa; respectively. And the θH was3.7MPa.d，1.3MPa.d,4.3MPa.d, and3.8MPa.d for Vicia angustifolia, V. amoena, V. unijuga and V. sativa, respectively.4) The germination process can be well described by thermal model and hydrotime model when the temperature is near to To and the water potential is higher.