Abstract: Osmopriming is often used to improve seed viability and stress tolerance. We quantified the osmopriming effects on drought tolerance of alfalfa (Gongnong No. 1) seeds, with polyethylene glycol (PEG 6000) as the priming agent. Four constant temperatures (10, 15, 20 and 25 ℃) and six drought levels (0 (distilled water as the control), -0.2, -0.4, -0.6, -0.8, and -1.0 bar) were set up for routine germination experiment. Alfalfa seeds were primed with polyethylene glycol (PEG 6000) and then dehydrated before germinati〖HJ*3〗on experiment. The hydrotime model was used to calculate the relevant parameters. The results showed that the osmopriming accelerated the germination rate of alfalfa seeds. The primed seeds had a fast germination speed under conditions of low water potential. With respect to water potential model parameters, the cumulative potential of the primed alfalfa seeds was lower than that of un-primed seeds. The lowest water potential of alfalfa seeds was decreased after priming. Our results indicated that osmopriming could decrease water potential requirement of seed germination and thus enable primed seeds germinate at lower water potential than unprimed seeds, which could improve drought resistance of seed germination.

Key words: Taxodium hybrid ‘Zhongshanshan’, antioxidase system, osmotic adjustment., photosynthesis, drought and recovery