System for Evaluating Root Uptake Capacity in Relation to Phytoremediation

Abstract

To evaluate root uptake capacity in relation to phytoremediation, a hydroponic system was newly developed for dynamic and simultaneous measurement of the rates of uptake of water and mineral nutrients by roots. The system consists of a circulation unit (an NFT bed, etc.) and a supply unit (a supply tank, a solenoid valve, etc.). A water-level sensor is installed in the circulation unit to detect the decrease in solution volume caused by root uptake. The circulation unit is automatically replenished with fresh nutrient solution from the supply unit by on-off action of the solenoid valve which is manipulated according to a signal from the water-level sensor. Therefore, the rate of water uptake can be evaluated from the supply volume per on-off action of the solenoid valve and the frequency of the on-off action. The rate of mineral nutrients uptake can be evaluated based on the quantity of nutrients introduced with the supplied fresh solution and the change in the nutrients concentration in the circulation unit. High accuracy of the evaluation system was demonstrated by the performance test. The system was applicable to short- and long-term measurement of uptake rates affected by fluctuating solar radiation and nutrients concentration in the greenhouse.