INFLUENCE OF HORIZONTAL CLINOSTAT ROTATION ON STARCH CONTENT AND STARCH DEGRADING ENZYMES IN LEAVES OF VICIA-FABA

Starch metabolism in leaves from Vicia faba was investigated after hor izontal rotation on a clinostat and compared to that of a vertically r otated control. Omnilateral gravistimulation during 8 h resulted in a loss of the chloroplast starch. This enhanced degradation of starch in chloroplasts led us to the conclusion that cells which are not suppos ed to be involved in gravity perception are, also sensitive to the con tinuous changes of the gravity vector direction. Since loss of starch was found to be correlated with an increase of the stromatal hydrolyti c enzyme activities, we suggest that horizontal rotation induces the e nzymatic degradation of the chloroplastic starch content. Furthermore, a simultaneous decrease of the extrachloroplastic starch degrading en zyme activities suggested that clinostat treatment affects enzymatic r egulation in the cell. Horizontal rotation on a clinostat is discussed as a possible stressor.