The relation between nutrient solution concentration and growth and ion absorption of peas (Pisum sativum L.)

Summary Studies have been made on the growth of peas in Richter's nutrient solution at concentrations of 1.0 (original solution), 0.1, 0.01, and 0.001; instead of employing flowing cultures, the solutions were vigorously stirred and continually replaced by fresh solution to maintain the concentration within close limits (±5%). Maximum growth occurred at the 1 and 0.1 concentrations; at lower concentrations growth was significantly depressed, but no deficiency symptoms were observed. The relative growth rate decreased regularly with decreasing concentration. No correspondence was observed between the reduction in solution concentration and that in the yield; for a concentration decrease of 1000 times, dry matter production was depressed only 4.85 times. With decreasing solution concentration the chlorophyll content however was depressed more than growth and at the lowest concentration was less than 1/80th of that in the original solution. As a result the net assimilation rate, calculated on the basis of dry matter production per unit chlorophyll content, increased sharply with decreasing nutrient solution concentration. Even at the lowest concentration the plants continued to grow throughout the course of the experiment.