Hydroponics in physiological studies of trace element tolerance and accumulation in plants focussing on metallophytes and hyperaccumulator plants

Abstract

Abstract Background When studying metallophytes and hyperaccumulator plants, it is often desired to assess the level of tolerance of a specific trace metal/metalloid in a putative tolerant species, to determine root and shoot accumulation of the trace metal/metalloid of interest, or to establish whether a trace metal/metalloid has an essential function. The use of hydroponics has proven to be a powerful tool in answering such questions in relation to the physiological regulation of metal/metalloids in plants. Carefully designing experiments requires considering nutrient solution formulation, dose rate regime, and environmental conditions, but this is often overlooked. Aims This review aims to bring together key information for hydroponics studies in physiological, evolutionary, and genetics/molecular biological research of trace metal/metalloid tolerance and accumulation in plants, focussing on metallophytes and hyperaccumulator plants. Conclusions It is not possible to define a ‘universal’ nutrient solution that is both sufficient and non-toxic for all plants, although it is often possible, dependent on plant species under study and the research question to be addressed, to ‘adapt’ commonly used ‘standard formulations’. Well-designed and executed hydroponics experiments can yield powerful insights in the regulation of essential and toxic metal/metalloid trace elements, and this extends far beyond hyperaccumulator plants.