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Less commonly, dicot leaf blades may have palmate venation (several large veins diverging from petiole to leaf edges). Finally, some exhibit parallel venation. [19] Monocot leaves in temperate climates usually have narrow blades and usually parallel venation converging at leaf tips or edges. Some also have pinnate venation.
Shape, margin and venation. Leaf Parts: – A complete leaf is composed of a blade, petiole, and stipules, but in many plants one or more might be lacking or highly modified. Blade – see lamina. Lamina – the flat and laterally-expanded portion of a leaf blade. Leaflet – a separate blade, among others, of a compound leaf
Leaves of most plants include a flat structure called the blade or lamina supported by a network of veins, a petiole and a leaf base; [1] but not all leaves are flat, some are cylindrical. [citation needed] Leaves may be simple, with a single leaf blade, or compound, with several leaflets.
The petiole is a stalk that attaches a leaf to the plant stem. In petiolate leaves the leaf stalk may be long (as in the leaves of celery and rhubarb), or short (for example basil). When completely absent, the blade attaches directly to the stem and is said to be sessile. Subpetiolate leaves have an extremely short petiole, and may appear sessile.
Reticulate venation seems to have appeared at least 26 times in monocots, and fleshy fruits have appeared 21 times (sometimes lost later); the two characteristics, though different, showed strong signs of a tendency to be good or bad in tandem, a phenomenon described as "concerted convergence" ("coordinated convergence").
They grow from their rhizomes and are often armed with prickles on the stems and/or leaves. Leaves are alternate and simple; and entire to spinose-serrate. Some members of this family have coriaceous (leathery) leaves. Venation of the leaves may be palmate to reticulate. A pair of tendrils often appear near the base of the petiole.
A primary vein, also known as the midrib, is the main vascular structure running through the center of a leaf. [1] The primary vein is crucial for the leaf’s efficiency in photosynthesis and overall health, as it ensures the proper flow of materials and structural integrity.
For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts. The homology of leaves is an easy conclusion to make. The plant morphologist goes further, and discovers that the spines of cactus also share the same basic structure and development as leaves in other plants ...