Problems in the Study of the Accumulation and Hyperaccumulation of Chemical Elements by Plants

摘要

Abstract The article is a review of internationally published works on the problems of the accumulation of chemical elements (CEs) by higher plants. The urgency of this research is due to the need for the theoretical study of the CE cycle and application-oriented aspects, e.g., the quality and safety of resource plants, the search for bioindicators and phytoremediators, estimation of the anthropogenic pollution level, etc. The confusion of a wide range of terminology and classifications in different research approaches demands some urgent solutions. The paper distinguishes carefully considered terminology, classification, and criteria for different plant based on different strategies of CE accumulation. In contrast to normal plants, resistance to high CE concentrations can result from different physiological mechanisms that lead to the formation of the main groups of excluders, bioindicators and hyperaccumulators. Special consideration is given to plants that are hyperaccumulator of certain CEs and to the criteria for the attribution of taxa to the given groups: threshold values of different CE contents, the concentration, translocation factors, and others. The problem of plant-surface contamination is also considered with respect to biological features and its impact on the assessment of the CE content. Some examples are given for incorrect interpretations of data on CE accumulation by plants. Based on the study results, it is established that the following factors should be taken into account for the most accurate estimate of the plant-accumulation potential, especially in order to specify hyperaccumulator plants: the viability of the studied population, threshold values that exceed the CE content for certain elements, high values of accumulations and translocation factors, and the degree of foliar contamination. A diverse and multiaspect approach to the plant-accumulation potential makes it possible to avoid a great deal of the current confusion.