Geographical variation in breaking the seed dormancy of Persian cumin (Carum carvi L.) ecotypes and their physiological responses to salinity and drought stresses

Seed germination is a critical stage in the life of crops. The laboratory experiments were conducted to determine whether the severity of seed dormancy in Persian cumin ecotypes and their response to salinity and drought stresses could be influenced the parent plant habitat. Seeds of three Persian cumin ecotypes (Alamut, Khabar, and Tandoureh) were collected from three protected areas in Iran. For each ecotype in seed dormancy-breaking study, the treatments included control, the prechilling of seeds for 20, 40, and 60 days at 5 degrees C and 10% relative humidity and the inundating of them into 0.72, 1.44, and 2.88 mmol GA(3) L-1 for 24 h. In the response to salinity and drought stresses study, two experiments were arranged separately as a completely randomized factorial design to investigate the effect of salinity and drought stress. In the 1st experiment, the prechilled seeds of three Persian cumin ecotypes were subjected to four salinity stress levels (0, 2, 4, and 6 dS m(-1)). In the 2nd experiment, those were subjected to four drought stress levels (0, 0.2,-0.4 and -0.6 MPa). All three ecotypes of Persian cumin had a deep dormancy. The ecotype of Alamut which has been harvested from a cool climate had a deeper seed dormancy than other ecotypes which have been harvested from a relatively warm climate. In all ecotypes, the highest germination rate and the lowest mean germination time were found where their seeds were prechilled for 60 days. The highest response to prechilling was observed in Alamut ecotype. The salinity and drought stresses resulted in a reduction in the rate and a delay in the speed of seed germination in three ecotypes of Persian cumin. The highest sensitive to salinity and drought stresses was observed in Alamut ecotype which its seed was obtained from where soil pH and EC are low. Here, habitat-correlated variation in Persian cumin seed germination response and stress tolerance was demonstrated.