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. 1967 Oct;42(10):1407–1412. doi: 10.1104/pp.42.10.1407

Effects of Temperature on Orthophosphate Absorption by Excised Corn Roots 1

O G Carter 1,2, D J Lathwell 1
PMCID: PMC1086738  PMID: 16656670

Abstract

The uptake of orthophosphate (32P) by excised corn roots, Zea mays L. was studied using roots grown on 0.2 mm CaSO4. Nine concentrations of KH2PO4 from 1 to 256 μm were used at temperatures of 20°, 30°, and 40°. Enzyme kinetic analysis was applied to the data obtained. Two apparent mechanisms (sites) of phosphate uptake were observed, 1 dominating at high P concentrations and 1 at low P concentrations. A Km of 1.36 × 10−4 and a Vmax of 177 × 10−9 moles per gram of roots per hour at 30° was calculated for the mechanism dominating at high P concentrations. Similar calculations gave a Km of 6.09 × 10−6 and a Vmax of 162 × 10−9 moles per gram of roots per hour at 30° for the mechanism dominating at low P concentrations. The Q10 for both mechanisms was approximately 2. Calculation of thermodynamic values from the data gave ΔF of − 5200 cal, ΔH of − 950 to − 1400 cal, and a enthalpy of activation (A) of 10,300 to 13,800 cal per mole for the mechanism dominating at high P concentrations. Similar calculations from the data for the mechanism dominating at low P concentrations gave a ΔF of − 7300 cal, ΔH of − 10,700 to − 8200 cal, and a A of 9300 to 18,900 cal per mole. If the dual mechanism interpretation of this kind of data adequately describes this system, then both mechanisms of P absorption by corn roots involve chemical reactions.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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