Absorption of Rubidium by Plants from Solution and Soils

The absorption by plants of Rb from soils and sand was measured. The Rb was added to the soil as RbCl, and in the sand culture various ratios of K to Rb were used. Corn was grown in the soils and the distribution in the plant and the soil determined. Beans were grown in the culture solutions, and the distribution of K and Rb measured in the various plant parts. The percent recovery of Rb by the corn plant from three soils was inversely related to the K in the soil. The K to Rb ratios in the plants showed high correlation with the HNO 3 ‐soluble K. The percent of the added Rb fixed against extraction with NH 4 OAc or HNO 3 during the 11 weeks growing period was small. Where bean plants were grown in sand culture with various ratios of K and Rb, the molar ratios of K and Rb in the plants differed somewhat from those in the solutions. There was also a significant difference between the K/Rb ratios in the various plant parts. Growth and fruit production in beans were reduced where the molar ratios of K to Rb were less than 5/1.