Effects of Seed Priming on Germination and Seedling Growth Under Water Stress in Rice

For disclosing the effects of seed priming with water and polyethylene glycol (PEG) on physiological characteristics in rice (Oryza sativa L.), the seeds of 4 rice cultivars were treated with H2O and different concentrations of PEG before germination. Primed or nonprimed (control) seeds were then germinated under drought stress conditions simulated with PEG in a serious of concentrations. The contents of proline, soluble protein (SP), total soluble sugar (SS), malonicdialdehyde (MDA), and the activities of phenylalanine ammonia lyase (PAL), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in the seeds or seedlings after 10-day stress were tested, and the indices for seed germination and seedling characteristics were determined. In seeds with priming treatments, the contents of proline and SP were significantly higher than those in the corresponding controls, and the contents of SS and MDA were significantly lower than those in the controls. Seed priming accelerated the process of glucose metabolism, enhanced the activities of PAL, SOD, CAT, and POD in the stressed seeds of all cultivars. Compared to hydro-priming, priming with PEG in a proper concentration had a better effect on seed germination and seedling growth under drought stress, and the optimal priming concentrations of PEG were 20% for Gangyou 527 (indica hybrid rice) and 10%–15% for Nongken 57 (conventional japonica rice). Even higher concentrations of PEG had negative effects on seed germination. Moderate priming intensity improved metabolism of rice seed, germination indices, seedling quality, and drought tolerance of seedlings under drought stress for all cultivars. However, such effects had limited capability, and severe drought stress inhibited germination and caused damages of rice seedlings. Rice cultivars had significant impact on priming effect, and indica rice showed better performance than japonica rice.

摘 要不同基因型稻种经水引发及聚乙二醇(PEG)渗透胁迫引发处理均能降低稻种丙二醛(MDA)含量, 促进可溶性总糖降解, 加快稻种内部糖代谢进程, 提高脯氨酸及可溶性蛋白质含量, 也有利于提高苯丙氨酸解氨酶(PAL)、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性, 引发效果较明显。且适度PEG引发稻种的效果明显好于水引发, 杂交籼稻在PEG浓度为20%的条件下引发效果最优, 而常规粳型水稻在PEG浓度为10%∼ 15%的引发条件下效果较好, 但超出最高PEG引发浓度的阈值, 会对稻种产生危害, 影响其正常萌发。引发处理后的稻种对不同程度水分胁迫的响应表明, 适当强度的引发处理利于激发稻种物质代谢、利于各水稻品种的萌发、幼苗形态指标及保护性酶等生理指标的显著提高, 而严重的水分胁迫均不利于稻种萌发; 表明引发处理虽能提高水分胁迫条件下种子活力, 但稻种激发自身对外界萌发环境的协调能力有限, 且不同品种间存在明显差异, 籼稻优于粳稻。