Borate absorption in excised sugarcane leaves

概要

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Borate absorption in sugarcane consists of a rapid and reversible influx into the mesophyll cells of the leaf which is completed within 20 mins. (Phase I), followed by a slower and irreversible accumulatory phase (II). Phase II uptake represents the summation of 3 absorption mechanisms, each dependent upon the external concentration. Highly specific mechanisms 1 and 2 transport borate across the initial barrier into the cells, reaction 3 carries the borate across the vacuolar membrane. Calcium is shown to be essential for maximun rates of borate absorption. All 3 reactions are inhibited by OH^- through a combination of competitive inhibition and irreversible disruption of cellular function or structure. Temperature changes over the range of 10-40° profoundly affect V_<max> and K_<m1>, but have no effect on K_<m2> and K_<m3>. Reactions 1 and 2 are unaffected by 50mM Cl^-, SO_4^<--> or H_2PO_4^-, whereas each of these anions competes with H_2BO_3^- for site 3. Specific metabolic inhibitors were used to delineate a linkage of mechanisms 1 and 2 to respiratory electron transport. Mechanism 3 is coupled to oxidative phosphorylation.
日本植物生理学会の論文