MITIGATION OF SYMPTOMS OF CA2+ DEFICIENCY BY BENZYLADENINE IN CUCUMBER - ION LEVELS, POLYAMINES AND CA2+-MG2+-ATPASE

The effect of Ca2+ deficiency and the role of benzyladenine in restoring membrane function were studied in cucumber plants. Symptoms of Ca2+ deficiency, including decreased levels of soluble Ca2+ in roots and changes in phosphate metabolism were mitigated by benzyladenine treatment of cucumber plants before and during Ca2+ starvation. Polyamine levels were determined in roots, leaves and shoot tips by high performance liquid chromatography. Ca2+ deficiency decreased putrescine and spermidine concentrations in the shoot tips and in the roots, however, after BA-treatment these were maintained at the control level in the roots. Plasmalemma was purified from the roots by aqueous two-phase partitioning. The activities of the Mg2+-ATPase and the Ca2+-Mg2+-ATPase (pH optimum 7.5) associated with the plasmalemma decreased in the Ca2+-deficient plants but they were also increased by benzyladenine treatment. Similarly, the decreased stimulation by externally added calmodulin of the Ca2+-Mg2+-ATPase was restored by benzyladenine.