Involvement of calcium ion in the stimulated shoot elongation of arrowheadtubers under anaerobic conditions

Shoot elongation of arrowhead (Sagittaria pygmaea Mig.) tubers was stimulat ed in anaerobic conditions. The anaerobic elongation was attributed to stim ulation of cell elongation in the middle of the shoots. The anaerobic elong ation of the shoots was severely inhibited by ethylene glycol bis(beta -ami noethylether) -N,N,N ' ,N ' -tetraacetic acid (EGTA), The EGTA inhibition w as completely nullified by exogenous CaCl2, which acts as an enhancer of an aerobic elongation. Moreover, calcium channel blockers, varapamil, diltiaze m and LaCl3, inhibited the anaerobic elongation enhanced by CaCl2, These re sults showed that calcium plays an important role in stimulating the elonga tion in anaerobic conditions. Incorporation of Ca-45 into the shoot tissues was measured to determine the involvement of calcium uptake in anaerobic e longation. Incorporation of Ca-45 into the cell sap, which was collected fr om frozen and thawed shoots after thorough washing with LaCl3, was signific antly stimulated in anaerobic conditions. Verapamil and diltiazem prevented the stimulation of Ca-45 incorporation in anaerobic conditions, These resu lts suggest that calcium uptake from the medium serves to enhance shoot elo ngation of arrowhead tubers under anaerobic conditions.