FACTORS AFFECTING THE ABILITY OF PLANTS TO ABSORB PHOSPHATE FROM SOILS

Abstract

Summary In water‐culture experiments of short duration the transfer of phosphate to plant shoots is reduced by ferric iron applied prior to or simultaneously with phosphate. The effect os more marked in barley than in rye. The retention of phosphate in roots is similar whether iron is applied simultaneously with or prior to phosphate. Variation in the concentration of phosphate which is supplied to plants has no corresponding effect on the retention of iron in roots. The evidence presented is compatible with the view that phosphate is restrained in roots by ferric ions which have already combined with immobile organic molecules. The atom ratio of iron to phosphate in the resultant complex appears to be I. No direct evidence is available to show whether reactions between iron and phosphate within plants contribute significantly to the interaction between the two irons which can occur when plants are grown in soils high in labile iron. This possibility cannot however be discounted.