NITRATE, VITAMIN-C, AND SUGAR CONTENT OF LACTUCA-SATIVA DEPENDING ON CULTIVAR AND HEAD DEVELOPMENT

The nitrate content of twenty-two butterhead lettuce cultivars pf gree nhouse and field- grown and the content of vitamin C and reducing suga rs of greenhouse lettuce were evaluated at three growth stages (stage ''A'' heads begin to form, stage ''B'' head formation is finished, sta ge ''C'' typical size, form and firmness of heads). The average head w eight of all greenhouse cultivars were at stage ''A'' 200 g, stage ''B '' 427 g, stage ''C'' 545 and of all field-grown cultivars at stage '' A'' stage ''B'' 345 g and stage ''C'' 514 g.