氯离子在土壤水分与作物生长关系研究中的指示作用

以小麦为试材,采用盆栽试验和氯离子指示技术,研究了不同土壤水分条件下,小麦在苗期对氯离子的吸收与累积特性和同期土壤中氯离子迁移特征。结果表明:(1)氯离子在小麦体内的累积与土壤含水量的关系密切,小麦苗期根系中氯离子累积量决定于根系与氯离子的接触几率,在植物地上部分的分配依赖于蒸腾强度;(2)在土壤含水量较低条件下,氯离子在根部累积明显,向地上部分移动不强,而在高含水量(18%)情况下,向地上部移动累积较为明显,氯离子在植物体中累积与分配关系很好地指示了土壤水分条件与植物生长之间关系;(3)在生长发育期间,当土壤含水量低于18%时小麦根系以伸长主动觅水,满足蒸腾需要为主;高于18%时,土壤水分移动以补偿根际蒸腾为主,土壤水分强烈的液态迁移存在着明显的临界含水量,可以用土壤剖面上氯离子含量的变化过程确定小麦根系水分利用的有效土层深度,以便准确地计算水分生产效率。因此,氯离子作为指示元素,在研究旱地土壤水分条件、水分移动能力等与作物生长的关系方面具有一定的可行性。

Indicating Role of Cl- in the Relation between Soil Water and Crop Growth

Wheat was hydroponically planted to study the characteristics of Cl~-uptake and accumulation of wheat and soil Cl~-movements in different soil water moistures at the seedling stage by Cl~-tracing.It was shown that(1) Cl~-accumulation had a close relation to soil water content in wheat and depended upon root-Cl~-contact probability at the seedling stage of wheat,and Cl~allocation to the aboveground part of wheat relied on transpiration intensity;(2) At low soil water content,Cl~-appeared to accumulate remarkably in the roots and did not showed strong movement towards the aboveground parts,but at high soil water content(18%),it moved remarkably towards the aboveground part.Thus,Cl~-accumulation and partition of plant parts could as the indicators to show the relation between soil moisture and plant growth;(3) During the development of wheat,the roots grew towards water by elongating to satisfy the transpiration requirement if soil water content was lower than 18% and when soil water content was above 18%,soil water movement was mainly oriented for the compensation to rhyizosphere evopo-transpiration;there existed clear-cut critical water content in strong movement of soil water in liquid form and thus Cl~-content in soil profile could be adopted to determine the soil depth at which wheat roots could effectively use water in order to make precise calculation of water production efficiency.Therefore,it was feasible to certain extent to use Cl~-as a indicating element to study the relation between soil water conditions and movement,and crop growth of dryland.