A leaf (
: leaves) is any of the principal appendages of a
vascular plant stem, usually borne laterally aboveground and specialized for
photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the
shoot
In botany, a plant shoot consists of any plant stem together with its appendages, leaves and lateral buds, flowering stems, and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spr ...
system. In most leaves, the primary
photosynthetic tissue is the
palisade mesophyll
Palisade cells are plant cells located on the leaves, right below the epidermis and cuticle that is the outermost layer of the leaf. In simpler terms, they are known as leaf cells. Palisade means "stake" in latin, they are vertically elongated a ...
and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of ''
Eucalyptus'', palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves are flattened and have distinct upper (