Limiting external concentrations of trace elements for plant growth: Use of flowing solution culture techniques

Abstract

Abstract To obtain accurate information on limiting external concentrations of trace elements for plant growth, the concentrations of the test element in the root environment must be known and adequately controlled for the entire duration of each experiment. It is desirable that other root environment parameters likely to have marked effects on the uptake of the test element (e.g. solution temperature, pH, and background composition of test solution) also be closely controlled. These conditions are difficult, if not impossible to achieve in solid culture media. However they may be closely approached in well stirred solution culture systems if sufficient attention is paid to the control of solution composition over time. Continuously flowing solution cultures permit a high degree of control of the root environment and provide the most practical means of establishing limiting external concentrations for trace element deficiency. Flowing culture techniques are also very suitable for quantitative studies of aluminium toxicity, since such studies require simultaneous control of pH and phosphorus concentration as well as aluminium concentration. For the study of other toxicites, flowing cultures may be used to good effect although it is sometimes possible to secure adequate control of the root environment by other means. Some design features of a modern flowing culture facility are described and the importance of using adequate solution flow rates discussed. The limited data on limiting external trace element concentrations obtained from flowing culture experiments is summarized.