Studies on molybdenum absorption and transport in bean and rice

The patterns of molybdenum (MoO(4) (2-)) absorption and transport were investigated in intact bean (Phaseolus vulgaris L.) and rice (Oryza sativa L. cv. I.R.8) plants. The mobility of MoO(4) (2-) absorbed by roots and by leaves was compared with that of a freely mobile element, Rb(+). Although MoO(4) (2-) absorption by bean roots was nearly as high as that of Rb(+), its transport to the shoot was considerably less. When MoO(4) (2-) was fed to one of the primary leaves, most of it was transported to the stem and root. Evidence obtained here showed that MoO(4) (2-) was mobile. Experiments with intact rice seedlings revealed large differences in the absorption and transport of MoO(4) (2-) between the plants grown in CaSO(4) and those in Hoagland solution. Molybdate uptake by excised rice roots was suggested to be an active process since it was greatly inhibited by a metabolic inhibitor. The presence of Mn(2+), Zn(2+), Cu(2+), CI(-), or SO(4) (2-) in the absorption medium reduced MoO(4) (2-) uptake which was markedly enhanced by the presence of Fe(2+).