Evaluation of cardinal temperature for germination of Grass Pea seed (Lathyrus sativus L.)

The seeds germination response to temperature is different between plant species. The germination process in different plants occurs in a wide range of temperature. The cardinal temperatures have an important role in the selection of suitable climate, time and places for seed planting. Given that the replacement of soybean by Green Pea is important for supply the required protein in dry lands. Evaluation of cardinal temperatures for germination of this plant can helps to better planting and timely seeding in the field. With this aim, an experiment based on completely randomized design was conducted with 4 replications in the faculty of agriculture of Birjand University. The treatments were 5, 10, 15, 20, 25, 30 and 35 degree of centigrade temperatures. The results showed that the maximum of germination rate was observed at 30 degree centigrade. In the temperature range of 15 to 30 degree centigrade observed high germination percentage. But, by reducing the temperature to below 15 degree of centigrade and increase it to more than 30 degrees, the germination percentage are significantly reduced. To determine the cardinal temperatures was used from three models including Intersected Lines, Quadratic Polynomial and Five Parametric Beta Regression. The Beta regression model was better described by temperature changes than the germination rate. In addition, the base, optimum and maximum temperature was 4.47, 28 and 35 degree of centigrade respectively.