Seed germination of dill (Anethum graveolens L.) in response to salicylic acid and halopriming under cadmium stress.

Seed priming is a technique which is potentially able to promote rapid and more uniform seed germination and plant growth as well. In this regards, the presowing effects of seed priming treatments were investigated on some physiological viz. seed germination, germination rate, radicle elongation, shoot elongation, radicle dry weight, shoot dry weight and vigor index. Seeds were subjected to two seed priming methods, hormopriming, and halopriming. Also, untreated seeds were used as control. Halopriming with -0.5 MPa of KNO3 and KCl and hormopriming with 100 mg/L of SA at 15 ˚C were used for 24 h in a factorial experiment with completely randomized design under laboratory conditions. The results showed that hormopriming (100 mg/L of SA) improved the germination rate (no significant difference with KNo3 and KCl), germination percentage, radicle elongation, plumule elongation, radicle dry weight, plumule  dry weight, and vigor index under cadmium stress (30 mg/L)  at 56.35, 11.9, 30.65, 30.33, 65.21, 71.42, and 46.16%, respectively. In all cadmium concentrations, the maximum of all germination parameters were related to the seeds primed with SA solution. While in primed seed by KNO3 and KCl treatments, exposure to 20 and 30 mg/L Cd decreased radicle length as compared to the control. Also, exposure to 30 mg/L Cd, KNO3 solution showed lower plumule length than control. The amount of reduction in radicle length in primed seeds with KNO3 solution and KCl solution was 11.88% and 6.18%, respectively, in 30 mg/L Cd. However, in all cadmium concentrations, germination percentage and rate were enhanced by KNO3 and KCl solubles.