The Transpiration Stream and Upward Translocation of Mineral Ions

Author Institution: Department of Botany, University of Arizona, TucsonCa46 and P32 were supplied simultaneously to young Phaseolus vulgaris L. seedlings grown in solution. After short periods of uptake, the Ca45/P32 ratios in opposite leaves and opposite leaflets were very similar. This relationship also held when Ca45 and Cs137 were paired. Ca45/P32 ratios in lateral halves of the same leaf were in good agreement, also. However, the basal halves of leaves always had higher Ca4B/P32 ratios than terminal halves. There was a negative acropetal gradient of Ca45/P32 ratio in the stem, but the ratio in the trifoliate leaves was higher than in the primary leaves. When roots were removed prior to supplying the radioisotopes, the Ca45/P32 ratios in the foliage and stems were lower than in plants with roots intact. The data obtained support the en masse flow concept of ion movement through the stem