Calcium-stimulated 32P Accumulation by Corn Roots
1972
Miller, Raymond J. | Peverly, John H. | Koeppe, D. E.
The polyvalent cation-stimulated uptake of phosphate (P) by plant roots has been acknowledged for some time. However, the mechanism of this stimulation and the site of activity have been poorly defined. Most evidence indicates that mitochondria are involved with ion uptake, thus suggesting the possibility that the polyvalent cation stimulation of P uptake by plant roots might be associated with mitochondria. This paper correlates the P accumulation (³²P) by isolated corn (Zea mays L.) shoot mitochondria and intact corn roots in the presence of various known inhibitors of electron transport or phosphorylation. In both intact roots and isolated mitochondria, Ca⁺² treatment stimulated the uptake of P when compared to either Mg⁺² treatment or control treatment. But a ratio of 4 mM Ca:l mM Mg produced optimal stimulation of P uptake when compared to other ratios of these cations. Oligomycin, azide, and 2,4-dinitrophenol reduced the uptake of P by whole roots, but only 2,4-dinitrophenol abolished the Ca⁺² preferential stimulation of P uptake. These results are compared to similar studies with isolated mitochondria and suggest that the accumulation of P by intact corn roots is at least partially controlled by mitochondria and that the Ca⁺² stimulation of P uptake by roots may be explained in terms of mitochondrial reactions.
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