Commercially grown and harvested crisp-head iceberg lettuce
(Lactuca sativa L.) were purchased from a local retailer and stored at
1.5 C. About 3000 stems were cored from the lettuce head. After removing the top and bottom portion of each stem, the middle portion was cut into discs with 2 mm thickness (about 2 g) each according to Toma s-Barbera n, Gil, Castan~er, Arte s, and Saltveit (1997). About 5e7 discs were obtained from each stem.