AMOUNT AND DISTRIBUTION OF CONSTITUENTS O F HEAD LETTUCE

The influence of developmental stage and head size on the amount of vi tamin C, beta-carotene, reducing sugars, NO3, P, K, Mg, Ca, Fe, Mn, Zn , and Cu in butterhead lettuce were investigated. This was done with g reenhouse and field grown head lettuce (cultivars 'Vivaldi', 'Soraya', and 'Ravel'). The nitrate, vitamin C, and beta-carotene contents decr ease, whereas the reducing sugars contents increase with progressional growth stage and head size. This is due to their differing outer, med ium, and inner leaf shares and to the changing ratio of these leafs du ring heading. Medium and inner leaves contain lower nitrate, vitamin C , and beta-carotene but higher reducing sugar contents in comparison w ith outer leaves. In the latter the mineral content is lower, with the exception of phosphorus. Differences of contents matter may attribute d to the development of varying sizes of head by cultivars.