Cataldo D A, Wildung R E
Environ Health Perspect. 1978 Dec;27:149-59. doi: 10.1289/ehp.7827149.
The use of plants to monitor heavy metal pollution in the terrestrial environment must be based on a cognizance of the complicated, integrated effects of pollutant source and soil-plant variables. To be detectable in plants, pollutant sources must significantly increase the plant available metal concentration in soil. The major factor governing metal availability to plants in soils is the solubility of the metal associated with the solid phase, since in order for root uptake to occur, a soluble species must exist adjacent to the root membrane for some finite period. The rate of release and form of this soluble species will have a strong influence on the rate and extent of uptake and, perhaps, mobility and toxicity in the plant and consuming animals. The factors influencing solubility and form of available metal species in soil vary widely geographically and include the concentration and chemical form of the element entering soil, soil properties (endogenous metal concentration, mineralogy, particle size distribution), and soil processes (e.g., mineral weathering, microbial activity), as these influence the kinetics of sorption reactions, metal concentration in solution and the form of soluble and insoluble chemical species. The plant root represents the first barrier to the selective accumulation of ions present in soil solution. Uptake and kinetic data for nutrient ions and chemically related nonnutrient analogs suggest that metabolic processes associated with root absorption of nutrients regulate both the affinity and rate of absorption of specific nonnutrient ions. Detailed kinetic studies of Ni, Cd, and Tl uptake by intact plants demonstrate multiphasic root absorption processes over a broad concentration range, and the use of transport mechanisms in place for the nutrient ions Cu, Zn, and K. Advantages and limitations of higher plants as indicators of increased levels of metal pollution are discussed in terms of these soil and plant phenomena.
利用植物监测陆地环境中的重金属污染，必须基于对污染物来源和土壤 - 植物变量复杂综合效应的认识。为了能在植物中检测到，污染物来源必须显著增加土壤中植物可利用的金属浓度。决定土壤中金属对植物有效性的主要因素是与固相相关的金属的溶解度，因为为了发生根系吸收，在根膜附近必须在一段有限时间内存在可溶态。这种可溶态的释放速率和形态将对吸收的速率和程度，或许还对其在植物和食用动物体内的迁移性和毒性产生强烈影响。影响土壤中可利用金属形态和溶解度的因素在地理上差异很大，包括进入土壤的元素的浓度和化学形态、土壤性质（内源金属浓度、矿物学、粒度分布）以及土壤过程（例如矿物风化、微生物活动），因为这些因素会影响吸附反应动力学、溶液中的金属浓度以及可溶和不溶化学物种的形态。植物根系是土壤溶液中离子选择性积累的第一道屏障。营养离子和化学相关的非营养类似物的吸收和动力学数据表明，与根系吸收养分相关的代谢过程调节特定非营养离子的亲和力和吸收速率。对完整植物吸收镍、镉和铊的详细动力学研究表明，在很宽的浓度范围内存在多相根系吸收过程，并且利用了用于营养离子铜、锌和钾的转运机制。根据这些土壤和植物现象，讨论了高等植物作为金属污染水平升高指标的优缺点。
