ISHS Acta Horticulturae 637: XXVI International Horticultural Congress: Advances in Vegetable Breeding
RELATIONSHIP BETWEEN THE NUTRITIONAL VALUE AND THE HEAD STRUCTURE OF LETTUCE |
| Authors: | B. Mou, E.J. Ryder |
| Keywords: | Lactuca sativa, vitamin A, β-carotene, vitamin C, ascorbic acid, calcium, iron |
| DOI: | 10.17660/ActaHortic.2004.637.45 |
| 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  -carotene (provitamin 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 -carotene 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 their implications for genetic improvement of the nutritional value of lettuce are discussed.
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