Vitamins in lettuce are plentiful. Its fresh leaves are an excellent source of several Vitamin-A and Î²-carotenes. Just 100 g of fresh, raw-lettuce provides 247% of daily vitamin A, and 4443 Âµg of Î²-carotene (Carotenes convert into vitamin-A in the body; 2 Âµg of carotene is considered equivalent to 1 IU of vitamin-A).
Xylem is one of the two types of transport tissue in vascular plants, phloem being the other.he most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called vessels. Xylem also contains two other cell types: parenchyma and fibers.
Schematic cross section of part of a leaf, xylem shown as red circles at figure 8. Xylem is one of the two types of transport tissue in vascular plants, phloem being the other. The basic function of xylem is to transport water from roots to shoots and leaves, but it also transports some nutrients. The word xylem is derived from the Greek word Î¾ÏÎ»Î¿Î½, meaning wood; the best-known xylem tissue is wood, though it is found throughout the plant. The term was introduced by NÃ¤geli in 1858.