Thermal time model analysis for seed germination of four Vicia species
野豌豆属4种植物种子萌发的积温模型分析

Aims The study aimed to: 1) investigate the accuracy of thermal time model in predicating seed germination response to temperature for different legume species after dormancy release; 2) compare temperature requirements for seed germination of different legume species from the Qingzang Gaoyuan. Methods The seeds of four Vicia species were germinated over the constant temperature range of 5–30 °C at 5 °C interval. The effects of temperature on seed germination were summarized in terms of the thermal time model for germination. Important findings The base temperature (Tb) did not differ significantly within each sub-population by regressing germination rate on sub-optimal temperatures. In contrast with Tb, the ceiling temperature (Tc) differed significantly within each sub-population by regressing germination rate on supra-optimal temperature in all species except Vicia sativa. These imply the base temperature for all individual seeds in the populations were relative constant, but the ceiling temperatures may vary within the sub-populations. Tb value estimated by repeated probit analysis was quite close to the value estimated by regressing germination rate within sub-optimal temperatures; however, Tc value estimated by this method was close to the value estimated with T50. Compared to two perennial legume species, annual legume species had lower Tb and Tc. The thermal model was accurate to predict the germination time course under different temperatures.