Holes around the wells in a PGA-agar plate. Wells were loaded with different amounts of polygalacturonase and incubated at 40°C for 24 h. The plate was stained with 0.02% Congo red and then destained with 1M NaCl. A, Control; B, 0.1U of polygalacturonase; C, 0.2U of polygalacturonase; D, 0.3U of polygalacturonase.