苜蓿种子萌发和幼苗生长对温度、光照和埋深的响应

紫花苜蓿(Medicago sativa)是世界人工草地重要的优良牧草。研究其种子萌发和幼苗生长对温度、光照及埋深等环境因子的响应,对苜蓿草地的种植及管理具有重要的实践指导意义。采用室内控制实验,分析了紫花苜蓿种子萌发和幼苗生长对恒温(10、15、20、25、30℃)、变温(6/15、10/20、15/25、15/30、20/30℃)、光照(12 h光照/12 h黑暗、24 h黑暗)以及埋深(1、2、3、4、5 cm)等环境因子的响应特征。结果表明,苜蓿种子的萌发温度范围宽,在供试的10种恒温和变温下萌发率为50%~88%,且温度处理对苜蓿种子的萌发率没有显著的影响;黑暗对苜蓿种子萌发有抑制作用,12 h光照/12 h黑暗条件下,苜蓿种子萌发率为69%~88%,而24 h全暗条件下为50%~77%,其中10、15、30、10/20和15/30℃温度下,光照处理均显著高于全暗处理。埋深1~5 cm的苜蓿种子出苗率没有显著差异,且幼苗株高、干重、鲜重均没有受到显著影响;埋深对苜蓿根生长存在显著影响,埋深1~2 cm根长度及重量均显著高于其他埋深处理。以上结果表明,苜蓿种子萌发的温度范围宽,恒温和变温下都有较高的萌发率,适合播种季节要求宽泛;黑暗显著抑制紫花苜蓿种子的萌发,田间种植苜蓿的最佳埋深为1~2 cm。

Seed germination and seedling growth of Medicago sativa in response to the variations of temperature,light,and burial depth

Medicago sativa is an important forage in global cultivated grassland.Aiming to provide management guide for M.sativa grassland,we investigated the responses of seed germination and seedling growth to the variations of important environmental factors(temperature,light,and burial depth).We compared seed germination of M.sativa at five constant thermal treatments(10,15,20,25,and 30℃)and five alternative temperatures(6/15,10/20,15/25,15/30,and 20/30℃),accompanied with two light regimes,i.e.12 h light/12 h dark and 24 h dark.Five sowing depths(1,2,3,4,and 5 cm)were carried out to explore the effects of soil burial depth on seed emergence and seedling growth of M.sativa.Results showed that M.sativa could germinate to 50%-88%within a large temperature range.Light availability significantly promoted seed germination,especially at 10,15,30,10/20 and 15/30℃.Seed germination ranged from69%to 88%under light treatment and from 50%to 77%under dark treatment.There were no significant differences in seedling emergence percentage across different burial depths.Fresh and dry weight of shoot,root length and weight of the 1-2 cm burial depth treatments were all significantly higher than that of 3-5 cm burial depth treatments.In conclusion,M.stativa could germinate under broad ranges of constant or alternating temperatures of 6-30℃,indicating that there was no strict season requirement for sowing seeds.Light significantly promoted seed germination of M.stativa.The suitable burial depth was within 1-2 cm.