Effect of salt and drought stress on germination characteristics of wild safflower (Carthamus oxycanthus)

Wild safflower (Carthamus oxycantha) is an important weed in the Saffron fields of Razavi Khorasan province. To study the effects of salt and drought stress on germination characteristics of this weed species, a factorial experiment was conducted in a completely randomized design with four replications. Factors included water potentials based on NaCl and PEG at 8 levels (0, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 -MPa) and temperature at 6 levels (10, 15, 20, 25, 30 and 35 °C). In both stresses, the greatest germination percentage and rate were observed at 20, 15, 25, 10 and 30 °C, respectively. The required water potentials for 50% reduction in germination percentage for salt stress at 10, 15, 20, 25 and 30 °C were 2.26, 3.64, 4.43, 2.63 and 1.98 -MPa, respectively, and similarly for drought stress were 1.65, 1.68, 1.92, 1.43, and 0.12 –Mpa, respectively. Changing water potential base on NaCl from 0 to -0.6 MPa, decreased optimum temperature from 19.99 to 17.43 °C. Optimum temperature decreased from 19.99 to 17.90 °C by changing water potential based on PEG from 0 to -0.2 MPa. In general and based on the results of this experiment, wild safflower was more sensitive to drought than salinity, and the potential for its spread in saline areas, as well as the management of this weed in saline lands should be considered.