CHANGES IN CUCUMBER ROOT ADENINE NUCLEO-TIDE CONTENTS DURING CALCIUM STARVATION

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Ca^<2+> starvation causes a remarkable increase in the level of alkaline phosphatase-isozyme which effectively hydrolyzes nucleoside di- and triphosphates but not nucleoside 5'-monophosphates, in cucumber roots (12). A comparison of adenine nucleotide contents between roots grown with or without Ca^<2+> was therefore attempted to see whether increased alkaline phosphatase plays a role in the regulation of nucleotide contents. ATP content of the Ca^<2+>-starved roots did not significantly change during the first 3 days following the removal of Ca^<2+>, and then rapidly decreased. On the other hand, the ATP content of the control roots increased, up to towfold, during the 3-day period, and thereafter decreased to the original level. The levels of both ADP and AMP decreased rapidly after Ca^<2+> starvation, while those in the control roots hardly changed throughout growth. With Ca^<2+> deficiency, the phosphohydrolyzing activities toward ATM and ADP greatly increased, but not toward AMP. Reedition of Ca^<2+> to the deficient medium, which reverses the increase in the activity, had no effect on the ATP content. Thus, Ca^<2+> starvation caused a great reduction in all adenine nucleotide contents of the cucumber roots. It seems, however, that the changes in the nucleotides may not be directly regulated by the alkaline phosphatase induced by Ca^<2+> starvation.
社団法人日本土壌肥料学会の論文