Submitted to: Horticultural International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 7, 2003
Publication Date: June 8, 2004
Citation: Mou, B., Ryder, E.J. 2004. Relationship between the nutrional value and the head structure of lettuce. Horticultural International Congress Proceedings. Acta Horticulturae 637:361-367. Technical Abstract: Crisphead lettuce has much lower vitamin A, vitamin C, calcium, and iron contents than leaf or romaine lettuce. This experiment was conducted to determine whether the low nutritional value is associated with the head structure. Heads of a crisphead lettuce cultivar "Salinas" grown in the field were kept open by hand, while leaves of a romaine lettuce cultivar "Lobjoits" were closed by tying with wire. These plants as well as the normal controls were analyzed for their nutritional contents. The content of vitamin A, Ca, and Fe was higher in the outer leaves than in the inner leaves of a normal lettuce head, while there was little difference in vitamin C content between the two classes of leaves. Artificially opening the lettuce head greatly increased its nutrient content to a level comparable to leaf or romaine lettuce. After the romaine lettuce leaves were closed, the levels of vitamin A and vitamin C dropped to a minimum and the contents of Ca and Fe were also largely reduced. These results suggest that the lower nutritional value of crisphead lettuce is due to the enclosure of its leaves in the head structure. The physiological basis of these findings and implications in genetic improvement of nutritional value of lettuce will be discussed.