短命植物独行菜种子萌发过程对低温的耐受特性

The Characteristics of Low Temperature Tolerance during Seed Germination of the Ephemeral Plant Lepidium apetalum(Cruciferae)

以独行菜(Lepidium apetalum)为材料,研究了其种子在萌发过程中耐受低温的特性,并对耐受低温的机制作了初步的探讨。结果表明:1.萌发至I、II、III期的独行菜种子经过冷诱导处理后,对零下低温-5℃、-10℃胁迫具有较强的耐受性,这种耐受性随萌发发展相对有所降低。2.独行菜种子萌发过程中胚根生长速度明显受到低温抑制,但也仍然能够生长。3.适当时间的低温层积能使独行菜萌发势显著提高,对终萌发率影响不大;过长时间的低温层积会使独行菜种子萌发势和最终萌发率降低。4.独行菜种子在4℃条件下不能萌发,但4℃层积2d的种子经25℃处理6h以上后,可耐受4℃低温而萌发,且萌发率随25℃处理时间增加而升高。如果25℃处理时间少于5h则不能在4℃低温下萌发。经4℃层积10d、再经25℃萌发处理1h的独行菜种子就能在4℃低温下萌发。综合分析认为独行菜种子不能耐受4℃低温萌发,原因可能是在露白前存在一个关键的生理阶段,在4℃胁迫逆境中不能越过这个阶段,该阶段之前与之后的萌发过程都能耐受4℃低温,因此对低温胁迫有良好的耐受性。这为探索早春短命植物耐受低温萌发的机制提供了新的思路。

Lepidium apetalum was used to explore the characteristics and mechanismes of low temperature tolerance during seed germination.The results showed that pre-treatment the seeds at 4℃ would improve the seeds viability after stressed by low temperature at-5℃ and-10℃ and the capability of seeds tolerance to cold temperature became weaker along with germination development.Although the growth of radicle was inhibited significantly at 4℃ during germination,the seeds could still survive and grow.With appropriate time of stratified at 4℃,germination pace would be improved and germination rate would not change,while both of which decreased if stratification lasted too long.Moreover,L.apetalum seeds were very sensible to the temperature during germination.It showed no germination at 4℃,while if seeds were stratificated for 48 hours at 4℃ and subsequently treated with 25℃ for more than 6 hours,seeds would germinate at 4℃ and the germination rate increased with the time of 25℃ treatment prolonged.If treatment at 25℃ was less than 5 houes,it showed no germinating.In addition,seeds with stratification for 10 days following 1 h treatment at 25℃ could also germinated at 4℃.The present study indicated that some pivotal genes that related with a key physiological stage before the onset of radicle protrusion might inhibite at 4℃,which resulted in L.apetalum seed could not germinate at 4℃.Except that physiological stage,the L.apetalum seed had a strong tolerance to low temperature at other germination stages.This experiment provided a new way to explore the germination mechanism of ephemerals plants seeds at low temperature.