SWELLING BEHAVIOR OF CELL-WALL AND STARCH IN POTATO (SOLANUM-TUBEROSUM L) TUBER CELLS .1. STARCH LEAKAGE AND STRUCTURE OF SINGLE CELLS

Continuous starch leakage was observed during 120 min of boiling of po tato tuber tissue. The leakage was higher in cortex than in pith tissu e and in stored than in fresh potatoes, and it increased during boilin g up to similar to 6 mg/g. Light microscope observations revealed that upon immersion of separated, boiled, dried and rehydrated cells (BDC) in water at room temperature or in an aqueous solution of up to 50% e thanol, the cell wall (CW) swelled to a higher average volume (2.5 x 1 0(-3)mm(3)) than the starch (1.2 x 10(-3)mm(3)). Above this ethanol le vel, the difference between the CW and the starch is diminished dually until, in 100% ethanol, the BDCs were not swollen (<1 x 10(-3)mm(3)); below 50% ethanol, the starch swelling increased relative to the CW s welling, and at 100% water (at 70 degrees C) the starch occupied the e ntire cell lumen (between 37 and 50 x 10(-3)mm(3)). The ultrastructure of gelatinized starch was seen as a swollen amorphous body, and extru sions of starch were seen between the main starch mass and the CW. At a high swelling pressure, cytoplasmic remnants and coagulated proteins were pressed compactly between the starch mass and the CW.