leaf characteristics of life

5.60) appears to be a simple leaf with an undivided lamina and winged petiole. It gives rise to lateral veins along its entire length Tike the plumes of a feather. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. In several species of Acacia found in the deserts of Australia (e.g., A. longifolia, A. glaucescens, A. recurva, A. auriculiformis), the bipinnate lamina is absent. Such an arrangement is called Kranz anatomy. Share Your PDF File The centre contains a number of vascular bundles which are embedded in a parenchymatous ground tissue. The leaf base is commonly sheathing, that is, covering the stem partially or completely. The cell walls are thin but are suberised and un-wettable in many species. 3. In Nerium or Oleander, the lower surface bears deep depressions called crypts (stomatal crypts). Sclerenchyma occurs in patches inner to both the upper and lower epidermis. The cells are thickened on the free side where silica and cutin are deposited. Collenchyma or sclerenchyma occurs towards the two epidermal layers for providing mechanical strength. 3. Characteristics of Leaf 3. A joint may be present between the tip of the petiole and the leaflets. For example, a branch of biology called virology studies viruses, which exhibit some of the characteristics of living entities but lack others. A leaf is green flattened lateral appendage of the stem or their branch that develops at the nodes Leaves ate arranged in acropetal succession and originates from the shoot meristem as lateral primordia. In this article we will discuss about:- 1. They occur in the aquatic carnivorous plants of Utricularia (Bladderwort). Instead, the undifferentiated mesophyll is similar to spongy tissue. Each vascular bundle is surrounded by a single sheath of compactly arranged parenchyma cells called border parenchyma or bundle sheath. Unlike other epidermal cells, guard cells contain a few chloroplasts. A distinction into upper and lower surfaces is absent. Share Your Word File 2. including leaf life-span, photosynthetic rate, specific leaf area (SLA; leaf area to dry mass ratio), and leaf nitrogen (N) concentration, and provide evidence for broad relationships between such traits and plant growth rates and stand-level processes. The interior of the pitcher is slippery. The cuticle is, however, less developed than at the adaxial epidermis. Mesophytic leaves may have stomata in the upper epidermis. Leaf morphology. Submerged hydrophytic leaves do not have stomata (e.g., Hydrilla, Potamogeton). 5.63). As the chloroplasts are more abundant in the compact palisade mesophyll cells than the loosely arranged spongy mesophyll cells, the upper surface of the leaf appears deeper green as compared to the lower surface. Isobilateral Leaf (Typical Monocot Leaf, Fig. 5.59 F), e.g., Bombax (Red Silk Cotton, vern. The bulliform cells are also useful in the unrolling of leaf during its development. 0. In many legumes it is swollen. The remaining ground tissue is made up of non-green parenchyma. Life Skills. When simple, leaf is multicoatate, that is, it has a number of principal veins, In compound leaf, leaflets are borne jointly on the tip of the petiole. These leaves bear spores or sporangia, e.g., stamens (microsporophyll’s) and carpels (megasporophylls). Leaves of the successive nodes lie in the same plane so that only two rows are formed on the stem, e.g., Quisqualis (Rangoon Creeper), Syzygium (=Eugenia, lambolana, vem, jamun). The rachillae are arranged in a pinnate fashion on the Primary axis or rachis, e.g., Acacianilotica (vern. It is the arrangement of leaves on the stem or its branches (Gk. Plant leaves help to sustain life on earth as they generate food for both plant and animal life. The condition is called tristichous, tetrastichous, pentastichous, etc. The principal veins converge towards the apex of the lamina, e.g., Zizyphus, Smilax. Depending upon their orientation there are two forms: The principal veins converge towards the apex, e.g., Bamboo, Grass. Identify this leaf arrangement. It consists of large isodiametric cells which appear oval or rounded in a transverse section. (vi) An apical bud or a regular growing point is absent. This clearly shows that the leaf of Citrus is, in reality, a palmate compound leaf where the two lat­eral leaflets have been suppressed and only the central leaflet (the normal blade) is func­tional. Xylem consists of vessels, tracheids, xylem parenchyma and a few xylem fibres. The simplest type of such a phyllotaxy is alternate or spiral distichous in which the leaves of a branch form two alternate rows (e.g., Grass). Protection against transpiration by changing into phyllodes (expanded petioles) and forming spines. On the basis of life span or duration of a leaf on the plant, it may of three types. The simple leaf is unicostate, that is, it has a single principal vein or midrib. In many plants the two guard cells are associated with two or more specialized epidermal cells called accessory or subsidiary cells. The vascular bundles of ribs are thicker than those of lateral veins. Leaves of Bryophyllum, Begonia, etc. Share Your PDF File 5.59 A), e.g., Balanites, Hardwickia; (v) Unifoliolate (a single leaflet separated from the petiole by a constriction) e.g., Citrus (Fig. Hair may occur here and there. Definition of Leaf: Leaf is a green, dissimilar exogenous lateral flattened outgrowth which is borne on the node of a stem or its branch and is specialised to perform photosynthesis. Biology, Leaf, Plants, Structural Organisation. It consists of 1-3 layers of vertically elongated, parallel and closely placed columnar or cylin­drical cells. 2. The arrangement of veins and veinlet’s on the lamina of a leaf is called venation. In small vascular bundles the xylem is compact. (iv) An axillary bud is often present in the axil of the leaf. In Maize leaf the undifferentiated mesophyll occurs in concentric layers around vascular bundles having large centrifugal chloroplasts in its large bundle sheath cells. 5. The plan of venation is similar to that of a feather. including leaf life-span, photosynthetic rate, specific leaf area (SLA; leaf area to dry mass ratio), and leaf nitrogen (N) concentration, and provide evidence for broad relationships between such traits and plant growth rates and stand-level processes. Share Your PPT File. Hair may occur here and there. Veinlet’s are inconspicuous. The leaf is thrice pinnate. 6. The close relatives of Citrus possess trifoliolate leaves (Aegle marmelos, Fig. Petiole (= mesopodium) is a cylindrical or sub-cylindrical smooth or grooved stalk of the leaf which lifts the lamina above the level of stem so as to provide it with maximum exposure. (ix) The lamina possesses prominent vascular strands called veins. Veins and veinlet’s are skeletal as well as conducting prominences visible on the surface of lamina, especially the under surface in dorsiventral leaves. TOS4. 5.58): The leaf is divided only once in a pinnate fashion. Here the pinnate leaf is divided twice pinnately (Fig. They are found in Smilax at the free ends of adnate stipules (Fig. It is called rachis. Preview this quiz on Quizizz. The compactness of palisade tissue is directly dependent upon the light intensity to which the leaf is exposed. Sepals are protective and green, petals are coloured and attractive, stamens are pollen bearing structures or microsporophylls while carpels are ovule-bearing megasporophylls. Depending upon the pinnate or palmate venation, the incisions are known as pinnatifid, palmatifid, pinnatipartite, palmatipartite, pinnatisect and palmatisect (Fig. A bladder has sensitive hair, branched trigger bristles, a trap valve, internal and external glands for trapping and digesting small animals (e.g., Water Fleas).

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