Cardinal Temperatures for Germination of Roselle (Hibiscus sabdariffa)

Abstract

Roselle is an important medicinal and industrial plant of the family of Malvaceae, and is planted in vast areas of Sistan and Baluchestan. In a laboratory study, the effect of varying temperatures on seed germination of Hibiscus sabdariffa was investigated and minimum, optimum and maximum temperatures for its germination were determined 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 considered in each treatment. Cardinal temperatures for germination were determined consistent with three models (i.e., Intersected-lines Model, Five-Parameters Beta Model and Quadratic Polynomial Model). The traits measured were germination percentage, the speed of germination and mean germination time. The temperature effect on all the measured traits was significant. The results of the regression analysis showed that the best model in terms of cardinal point of this plant is the Five-Parameters Beta Model. Given the results of this model, the minimum and the optimal temperatures for the germination of Roselle are 4.04°C, and 29.83° C, respectively.  

Keywords

• Cardinal temperatures
• Germination rate
• Plant medicinal
• Regression models