RADIAL TRANSPORT OF PHOSPHATE IN CORN ROOTS : Mechanism of Transport of Phosphate Estimated by the Turnover Rates of Intermediate Compounds

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The mechanism of radial transport of phosphate in the corn roots was studied in applying the ^<32>P and ^<33>P double labelled tracer method. Corn roots fed with ^<33>P for 24h were supplied with ^<32> for a few minutes. relative specific activities (RSA,^<32>P/^<33>P) of the various phosphate compounds in the cortex, stele, and xylem exudate were determined. In the cortex, RSA of ATP and ADP increased at the beginning most rapidly. After 18 min, RSA of G6P and F6P showed the highest value, followed by PGA, ATP, FDP, ADP, and P_i. In the stele, RSA of orthophosphate showed the highest value only within 2 min and the lowest after 4 min. After 18 min, the RSA of G6P+F6P showed the highest value followed by PGA, FDP, P_i. RSA of phosphorus in the exudate increased rapidly after 8 min. The value of RSA was almost the same as that of G6P in the cortex and G6P+F6P in the stele, and it remained higher than that of other organic phosphate compounds after 100 min. From these results it is considered that the phosphate absorbed from the roots is transformed into ATP and other organic forms of phosphate and is removed into stele via the protoplasmic flow. Some of the inorganic phosphates are stored in the vacuoles and some are transported with other phosphate compounds. Among the phosphate compounds, G6P accumulates in the cortex and stele and due to the dephosphorylation process that takes place in the stele the phosphate is leaked into the xylem exudate.
社団法人日本土壌肥料学会の論文

RADIAL TRANSPORT OF PHOSPHATE IN CORN ROOTS : Mechanism of Transport of Phosphate Estimated by the Turnover Rates of Intermediate Compounds

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