There are two basic forms of leaves that can be described considering the way the blade (or lamina) is divided. Stipules fuse to form a sheath or ochrea around the stem, e.g., Rumex, Polygonum. Some leaves have a petiole, which attaches the leaf to the stem; leaves that do not have petioles are directly attached to the plant stem and are called sessile leaves. Protection from browsing animals by producing spines, e.g., Barberry, Opuntia, Argemone mexicana, etc. 2. The upper or adaxial surface which faces the sun is darker than the lower or abaxial surface. The remaining ground tissue is made up of non-green parenchyma. Parenchyma cell are the main representative of the ground tissues system found in all plant organ. The arrangement of veins and veinlet’s on the lamina of a leaf is called venation. In aquatic plants, the intercellular spaces in the spongy parenchyma help the leaf float. Leaf: Characteristics, Types, Duration and Insertion, Dorsiventral Leaf, Isobilateral and Centric Leaf | Plants, Main Parts of a Typical Root (With Diagram) | Plants. The petioles of Garden Nasturtium (Tropaeolum majus, Fig. (D) conduction. 12. Such a palmate compound leaf, with one functional leaflet, is called unifoliolate compound leaf. The cells consist of isodiametric, thin walled and equally expanded cells. Small, free, green outgrowths, e.g., Shoe-flower (Hibiscus rosa-sinensis). In hot climates, plants such as cacti have succulent leaves that help to conserve water. The two stipular spines of Zizyphus are unequal with one straight and second bonked. Parenchyma in the primary plant body often occurs as a continuousmass, such as in the cortex or pith of stems, roots, mesophyll and flesh offruits. Hair may occur here and there. The flattened lamina or leaf blade is supported by veins and veinlet’s which contain vascular tissues for con­duction of water, mineral salts and prepared food. The leaflets or pinnules are borne on tertiary axes (Fig. The long axes of these parenchyma cells lie at right angles to the surface of the leaf. Protoxylem being present on the upper or inner side, xylem is endarch. 4. The base is filled up with a digestive fluid. CC licensed content, Specific attribution,,,,,,,,,,,,, In bulbs the fleshy scales are actually the leaf bases, e.g., Onion. A large number of chloroplasts are present in each cell. Spines of Zizyphus and Acacia are modified stipules. The veins branch dichotomously. A waxy cuticle covers all aerial surfaces of land plants to minimize water loss. 5.63). Answer and Explanation: The cross-section of a leaf shows the upper epidermis, mesophyll, and lower epidermis. In epiphytic Dischidia the whole leaf is changed into an open pitcher for storing rain water. The finer branches do not form a reticulum. However, in case of water deficiency the bulliform cells lose water and become flaccid. Xylem is formed of vessels, tracheids and xylem parenchyma. They have chloroplasts but fewer than present in the palisade paren­chyma. The cells of the palisade parenchyma are cylindrical. Lamina (= epipodium) or leaf blade is the terminal thin, expanded, green and conspicuous part of the leaf which is specialized to perform photosynthesis. Below the palisade parenchyma are loosely-arranged cells of an irregular shape. In Begonia, adventitious buds develop in the region of injury. There are two surfaces— adaxial (ventral, upper) towards the upper part of stem and abaxial (dorsal, lower) towards the lower part of stem. Leaf base (= hypo podium) is the lowermost part of the leaf by which the leaf is joined to the node of the stem. 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