Sucrose Leakage from Isolated Parenchyma of Sugar Beet Roots

The kinetics of sugar efflux from slices of sugar beet roots was investigated using washing solutions of different osmotic pressure and calcium concentration. The leakage of sucrose is strongly reduced in solutions of high osmotic pressure (>0·8 MPa) or high calcium concentration (10 mM). Turgor-dependent necrosis of parenchyma cells (plasmoptysis) is the main cause of sucrose efflux from the tissue in hypotonic media with low calcium activity. This was shown by good correlation between the percentage of leaked sucrose and the percentage of tissue water, which was in the free space after the washing procedure. The kinetics of sugar leakage from beet root parenchyma is no basis for the estimation of the sugar contents of the free space or the cytoplasm in situ.