关键词: 分蘖洋葱, 黄瓜, 套作, 土壤微环境

Abstract: 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.

Key words: Chinese onion, cucumber, intercropping, soil micro-environment