Cardinal Temperatures for Germination of Roselle (Hibiscus sabdariffa L.)

Roselle is an important medicinal and industrial plant of the family Malvaceae, which is planted in vast areas of Sistan and Baluchestan. In an a laboratory study, the effect of temperature on seed germination of Hibiscus sabdariffa and temperature minimum, optimum and maximum germination, in a completely randomized design with four replications. For this purpose, Temperatures 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 °C were determined in each treatment. Cardinal temperatures for germination Based on three models Intersected-lines Model, Five-Parameters Beta Model and Quadratic Polynomial Model Respectively. Traits measured where germination percentage, speed of germination and mean germination time, the temperature effect on all traits were significant. The results of the regression analysis of the data showed the best model in relation to the cardinal point of this plant the Five-Parameters Beta Model and according to the results of this model, the optimal temperature for germination of Roselle 4.04°C, the minimum required temperature 29.83° C.