Effect of light and temperature on seed germination of Calotropis procera L.

Calotropis procera is a perennial shrub adapted to arid climate which is widely used for desert reclamation practices. Seed germination is a critical stage of plant survival. Seeds of Calotropis procera have poor germination rate under field condition. To investigate the effects of light and temperature on seed germination of Calotropis procera, a seed germination experiment was established using a complete randomized block design with four replicates. The treatments were included two levels of light (light and darkness) and 9 levels of temperature(0,5, 10, 15, 20, 25, 30,35,40◦C). The ANOVA results showed that light treatments have no significant effect on seed germination rate. The seed germination rate, seedling length and dry weighthave increased with an increase in temperature level from 5 to 30◦C but decreased at higher temperater levels (30-40◦C). The highest and lowest germination rate were recorded at 30◦C and 20◦C, respectively. The highest seedling length and dry weight were obtained at 35◦C and the lowest ones at 20◦C. The regression line fitted to relative germination rates at 20◦C to 30◦C and 30◦C to 40◦C showed that germanation threshold of Calotropis procera seed is about 30◦C. Germination of Calotropis procera seed was was negatively affected by temperature of above 30 and below 20◦C. In conclusion, suitable period of time for seed germination and seedling stablishment of Calotropis procera seems to be very short.