The effect of rubidium sulphate and palladium chloride on the growth of plants

SUMMARY. 1. Comparisons have been made between the action of rubidium sulphate and palladium chloride on the growth of barley, wheat, oats peas and beans in complete nutrient solutions. 2. Over a wide range of concentrations rubidium sulphate was not found to exercise either a beneficial or a harmful action on the growth of any of the species tested. The germination of the seeds was likewise not affected. 3. No benefit was derived from palladium chloride, but at a comparatively low concentration a harmful action occurred which became more intense with increasing concentration. Stunting of the main root and laterals was a characteristic feature of this toxicity. With the lower concentrations the check was temporary, and the roots eventually made normal growth, as good as that in the control plants. With increasing amounts of pallahum chloride the poisoning effect became more persistent, until a concentration was reached which did not allow of any root or shoot recovery. 4. The tolerance of palladium varies with the species, as was indicated b. the measure of recovery. Barley appeared to be the least, and oats the most sensitive of the three cereals tested. Peas responded at much the same concentrations as barley, but broad beans made so complete a recovery from the initial checking that the dry weights were ultimately not reduced even by the strongest concentration tested, the plants being indistinguishable from the controls. 5. The effect of palladium poisoning was similar whether the seeds were germinated in the presence of palladium or whether the seedlings were not introduced to it until they were about a week old.