THE UPTAKE OF PHOSPHORUS BY BEAN PLANTS WITH PARTICULAR REFERENCE TO THE EFFECTS OF IRON

Abstract

The absorption of P by bean plants as influenced by variations in the Fe content and in the pH of theculture medium was investigated. Absorbed Fe ties up a portion of the "seed P" in an unusable condition and in the culture soln. a precipitate of FePO4 may be formed in or on the roots. When the P content of the nutrient soln. is low, this precipitate may remove P from the soln. and hence decrease the amt. available to the plant. When the amt. of P in the soln. is higher, the precipitate may retard the flow of P to the actively growing plant parts. As the P concn. of the nutrient soln. is increased, roots, stems, and cordate leaves continue to build up in P content even after trifoliate leaves are being adequately supplied. There exists a characteristic uptake of P for each pH level of the nutrient medium. The absorption and translocation of an aliquot of marked P (P32 plus p31) was measured. The use of this technic indicated that the % gain in P is dependent upon the amt. of P present in the nutrient medium and that those plants growing at the highest nutrient levels acquire the most P. Roots gain P in direct relationship to the Fe cone. of the nutrient medium whereas the trifoliate leaves gain P in inverse relationship to the Fe cone. of the nutrient mediums.