Effect of temperature and light length on the morphological traits of three falldormant class varieties of Medicago sativa

Low temperature and short light length are the main environmental factors causing the fall dormancy of Medicago sativa. An experiment was conducted in the laboratory to determine the effect of combination of different temperature and light length on morphological traits of three varieties of M. sativa with different fall dormancy classes. The major results of this study showed that the interaction effectiveness of temperature reduction and light length reduction on morphological traits of alfalfa varieties were significantly greater than single treatments（P0.05）. Temperature reduction and interaction between temperature reduction and light reduction decreased the branch numbers per plant, weakened stem growth, and made the leafage become long and slim for nondormant and dormant alfalfa varieties, as well as enabled the prostrate growth to become obvious. Reduction in light length and temperature significantly reduced the forage yield and quality of alfalfa varieties（P0.05）and light length reduction were more than temperature reduction.