(blade) 1. The usually flattened bladelike portion of a leaf, as distinct from the petiole and leaf base. The shape of the lamina and the nature of its margin are important taxonomic characters (see illustrations). Leaf laminas are usually the main photosynthetic organs and are structured accordingly (see palisade mesophyll , spongy mesophyll ). They are placed so as to make the best use of incoming light with the minimum amount of either overlapping or wasted space. This is particularly evident in a tree canopy. The pattern so achieved is termed the leaf mosaic and is mainly a result of * phyllotaxis. |
