The effects of salt stress on germination of Calotropis procera L. seeds

Calotropis procera L. is a perennial shrub adapted to arid regions which is extensively used for deserting recovery operations. Calotropis procera seed shows low germination under natural conditions. Germination and seedling establishment stages are critical phases for plant survival. In order to examine the salinity effect on Calotropis procera seed germination, a factorial experiment based on randomized complete block design was conducted with four replications. Salinity factor (NaCl and CaCl2 with the ratio of 5 to 1) had five levels:. 0, -0.01, -0.05, -0.1, and -0.15 MPa, which were examined as priming or without priming pretretments. Salinity (NaCl) had significant effects on germination percentage. Increasing salinity decreased germination percentage as well as germination rate and seedling length. Calotropis procera seed germination percentage was 99, 80, 55% in salinity levels of 0, -0.01 and -0.05 MPa, respectively, while it became zero with increasing salinity at -0.1 and -0.15 MPa. Priming with NaCl and CaCl2 (-0.1 MPa) for four days had significant effects (P < 0.01) on the germination percentage. Priming improved the seedling characteristics in all samples, especially in -0.05 Mpa, whereas a reduction was observed in all germination traits with decreasing osmotic potential.