Adaptation strategies of seed germination and seedling growth to sand dune environment
综述了植物沙生适应机制的研究及其进展.一些植物的种子在刚成熟时具有休眠特性.种子需要适度沙埋促进萌发并实现幼苗定居，但过度沙埋则会抑制种子萌发和出苗.在沙层深处，没有萌发的种子会进入休眠状态，形成土壤种子库.幼苗通过增加节数和延长节间来适应沙埋.沙埋深度超过植物的忍耐限度会抑制幼苗生长，甚至导致幼苗死亡.沙生植物必须适应其他环境因子，如盐风与土壤盐分、昆虫采食、土壤养分亏缺等，才能在沙丘上成功生长.沙蚀可导致幼苗根系暴露并干燥脱水.一些沙漠植物的幼苗在萌发后可忍耐一段时期的干燥，水分条件得到满足之后，幼苗能够恢复生长.
Sand dune plants possess many adaptation strategies to withstand sand environment,e.g.,some desert plant seeds are dormant when matured,which helps them to escape from unfeasible environment conditions and be preserved as seed bank.The seed germination and seedling establishment of psammophytes need moderate sand burial,while excessive burial will inhibit seed germination and seedling emergence.Seeds without germination in deeper sand are in enforced dormancy,and form soil seed bank.Sand dune plant seedlings could tolerant finite sand burial by increasing the number of nodes per culm and elongating internodes.When the seedlings are partially buried,they could survive through the maintenance of photosynthesis organism.Once sand burial exceed the threshold of the plant,seedlings growth will be restrained and the growth ability even permanently lost.Other factors such as salt spray,insect herbivory,and lack of soil nutrients also affect seed germination and seedling establishment.The precipitation in desert and sand land is unpredictable and irregular.Sand erosion leads roots be exposed to the air and dehydrated to die.However,seedlings of some desert plant have the ability to tolerate desiccation for a period of time after germination.Once there is rain,the seedlings will rivive.
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