Effect of priming on seed germination and seedling growth

Germination and seedling growth of Medicago sativa seeds primed with H2O, PEG-6000(-0.6 MPa), KNO3 (2%), GA3 (100 mol·L-1) and CaCl2 (2%) were determined under different temperature, salt and water stress. The results showed that: 1) All priming treatments significantly increased germination percentage at low water potential but not under the other conditions except for a significant increase at severe salt stress condition by KNO3 priming. 2) Priming significantly decreased the average germination time except for at 10 and 15 ℃ after CaCl2 priming, or at high salt stress after PEG priming. 3) Effects of priming on seedling radicle and shoot growth varied with priming treatments, varieties and test conditions. For example, hydropriming significantly increased radicle growth at 10 ℃, but showed no effect under the other conditions. Hydropriming significantly increased shoot growth at 10 ℃ or under severe salt stress condition. In addition to hydropriming, all priming treatment significantly promoted alfalfa shoot growth under low water potential, among which KNO3 priming exhibited the optimal effect.