Abstract: In order to understand the influence of both NaCl and osmotic PEG4000 stress on seed germination of Medicago sativa, five varieties of alfalfa seeds were selected to determine their germination rates and radicle lengths. Results show that germination rate and radicle length of alfalfa seeds have similar trends between five varieties under both NaCl and osmotic PEG4000 stress. NaCl can significantly reduce alfalfa seed germination rate, while PEG4000 has little influence (P<0.05). Germinated seeds show short, thick radicle length with NaCl stress, while they appear as thin, long radicle lengths with PEG4000 stress. Medicago sativa 'Zhongmu No.3’ shows less influence with NaCl stress than osmotic PEG4000 stress. Relative conductivities are reduced with NaCl stress while proline content is significantly increased with PEG4000 stress (P<0.01). Chlorophyll contents show the lowest levels with NaCl stress, but show a slight rise with PEG4000 stress. In summary, salt stress appears more harmful than drought stress for Medicago sativa 'Zhongmu No.3’.

Key words: Medicago sativa, NaCl, PEG, Ostomic stress, Seed germination

摘要： 为比较等渗的NaCl和PEG溶液模拟盐分和水分胁迫条件对紫花苜蓿(Medicago sativa)种子发芽过程的影响,选取5个紫花苜蓿品种分别对其种子发芽率和胚根长度进行统计。结果表明:5个品种受2种胁迫后,其发芽率和胚根长度变化趋势相似,即NaCl能显著降低紫花苜蓿种子的发芽率(P<0.05),PEG4000则影响不大;其胚根长度变化趋势为:受NaCl胁迫后胚根较粗短,PEG4000胁迫后细而长。对受2种胁迫影响较小的中苜三号发芽后其电导率、脯氨酸和叶绿素含量的测定发现,胁迫后电导率均增大,但受NaCl胁迫处理的差异极显著(P<0.01);游离脯氨酸积累均增高,其中PEG4000胁迫处理后,脯氨酸的积累极显著增高(P<0.01);中苜3号受等渗NaCl胁迫后,叶绿素含量最低,对照是其含量的2.3倍(P<0.01),受PEG4000处理后叶绿素含量有所上升,但与对照相比差异不显著。由此说明等渗胁迫条件下,盐胁迫比干旱胁迫对中苜三号的伤害更大。

关键词: 紫花苜蓿, NaCl, PEG, 等渗胁迫, 种子发芽