Morphology Leaf

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The flat, thin sheet expanded, containing most of the chloroplasts, called sheet or leaf lamina. It has two faces: the adaxial, upper, ventral, beam or epifilo directed towards the apex, and the abaxial side, bottom, back, back or hipofilo directed towards the base of the stem. When both sides are the same color, the leaf is called concolora, when they are of different colors, usually green adaxial is darker, called discolora.

Many leaves have a proximal stalk, the petiole or (eg ferns) Stipe. Is generally narrow, may be cylindrical or depressed in the upper face, or flattened width and Citrus . In many cases the leaves have no petiole, the blade is attached directly to the stem and the leaf is called sessile or seated. When two sessile leaves inserted in each node , sometimes are joined together completely surrounding the stem such as carnation ( Dianthus ). 14
Many species-like thickenings of joints, termed pulvinos , which are located in the base or apex of the petiole, or pulvinules if they are located at the base of the compound leaves petiolules. Both types of drusen are swollen and have a wrinkled surface, ...
... functionally, are related to reversible movement of the leaves that occur in response to stimuli: the dynasties . The pulvinules of certain species of the genus Mimosa leaves move in response to tactile stimuli. 14
A sheet or part of the blade, usually in the base, partially or completely enclosing the stem above the node is a leaf sheath , as occurs in grasses and many Apiaceae . A pseudopecíolo is a stalk-like structure arising from a leaf sheath and blade, as found in several monocots, such as bananas and bamboos .
The leaves contain one to many vascular bundles, the ribs. A conductive tissue with similar function (although not really vascular) is present in the moss .

Many leaves have stipules , a pair of leaf-like appendages on both sides of the leaf base. Stipules foliaceous organs may appear as, spines, glands, hairs or scales. If the stipules are present, the leaves are said set. A specialized structure, escariosa, which is above the knots in some members of the family Polygonaceae , is interpreted as a modified version of a stipule and is called ocrea . Stipules that mimic the structures at the bases of the leaflets are called stipels (eg Thalictrum or in some leguminous plants). Stipels stipules and may in some cases, function as protection for the development of leaf primordia. 15 16 Stipules may be free or side , if not stick to the petiole and are linked only to stem ; adnatas , petiole or vaginal if welded to the petiole in a longer or shorter distance; interpeciolares or cauline leaf stipules when the opposite is welded at its point of contact; intrapetiolar or axillary when the stipules of the same sheet are welded above the petiole, opposite where the stipules the same sheet are welded by turning the side opposite the petiole; ambiguous when welded to the stem and petiole.

The leaves are extraorinariamente varied in form, which is usually characteristic of each species , though it varies widely among individuals and even within the same individual. One can distinguish, first, between presenting shojas petiole - leaf petioles - of which do not have it - sitting or sessile leaves -. In the latter case the blade tends to have a wider base contact with the stem which supports the blade - leaves clasping - but surrounds it to the point where the branch behind the two lobes are welded to the sheet, it is called perfoliada . Leaves whose blade extends downwards forming a flap along the petiole and internode called decurrent .
In response to the shape of blade, the following designations apply to the leaves: round, oval, elliptical, oblong, lanceolate, spatulate, wedge-shaped, linear. As special forms which may be mentioned the leaves peltate, cordate, kidney-shaped and aflechadas.

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