A hibiscus leaf exhibits two different shades of green on its upper and lower surfaces. Edit. Before sharing your knowledge on this site, please read the following pages: 1. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? A distinction into upper and lower surfaces is absent. The swollen leaf base is known as pulvinus. It consists of 1-3 layers of vertically elongated, parallel and closely placed columnar or cylindrical cells. They enclose large cavities or intercellular spaces which are connected with the atmosphere through the stomata. They occur in marginal notches in intact leaf of Bryophyllum. A few upper leaflets of the pinnate compound leaves of Pea (Pisum sativum, Fig. It is chlorenchymatous. Succulent leaves occur in plants of saline and xerophytic habitats, e.g., Aloe, Agave, Bryophyllum, Portulaca. Lai Patti), the leaves borne near the cyathia are brightly coloured to attract insects for pollination. The leaf apex gives rise to a coloured lid for attracting the insects. What are the different sources of air pollution? A number of parallel running vascular bundles are embedded partially in the sclerenchyma found towards the lower side. Depending upon the number of the leaflets present, a palmate compound leaf is called: (i) Multifoliolate or digitate (five or more leaflets, present at the tip of petiole, Fig. (x) The leaves are generally green because of the presence of chlorophyll. These are small leaf like structures in whose axil flowers develop. In Barberry, the leaves of the main stem are modified into branched 3-5 rayed spines. 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. The leaf is thrice pinnate. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. (a) Caducous or fugacious: The leaves which fall soon alter their appearance, e.g., Opuntia. (vi) The leaf base may have two lateral outgrowths called stipules. Stipules are foliaceous in Lathyrus aphaca to take part in photosynthesis. The leaf is the site of photosynthesis in plants. (vii) The leaf base may possess two lateral outgrowths called stipules. Crop productivity is determined by rate of leaf production, periods for which they are retained on the plants, their orientation to light, shape, area, etc. (xi) Leaf bears abundant stomata for exchange of gases. It bounds the leaf on the lower surface. Phloem lies towards the lower side while xylem is found towards the upper side. What is the reserve food material in red algae? Stipules are fused from their inner margins to become axillary, e.g., Gardenia. 3. In small vascular bundles the xylem is compact. Functions 7. Some plants show developmental heterophylly. The various functions of the epidermis are: (iii) Loss of water vapours or transpiration through stomata, (iv) Reducing the rate of surface transpiration by the presence of cuticle, (v) Reducing the rate of transpiration by forming a stationary layer of air with the help of hair. The leaves which fall soon alter their appearance, e.g., Opuntia. A distinct layer of cuticle lies on the outside of the epidermis. 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. On the basis of life span or duration of a leaf on the plant, it may of three types. Therefore, mesophyll constitutes the photosynthetic tissue of the leaf. These are first few leaves of a stem that differ from the- rest, e.g., in Citrus and pteridophytes. Mesophyll is not differentiated into palisade and spongy tissues. 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. 2. Typically, a leaf consists of a broad expanded blade (the lamina), attached to the plant stem by a stalklike petiole.In angiosperms leaves commonly have a pair of structures known as stipules, which are located on each side of the leaf base and may resemble scales, spines, glands, or … 76% average accuracy. Prickles occur at various positions (margins, apex, surface) on the leaves for the same purpose, e.g., Aloe, Solanum surattense (= S. xanthocarpum), Carthamus oxycantha. Leaf base may be broadened to enclose the stem. Importance. (i) Pinnate or Unicostate Parallel Venation: There is single principal vein or midrib that runs from base to the apex of the lamina. Protoxylem being present on the upper or inner side, xylem is endarch. Dharek, Drek). (i) These are dissimilar, lateral outgrowths of the stem. Veinlet’s are inconspicuous. TOS4. Welcome to BiologyDiscussion! Leaf base is often indistinguishable from the petiole. Sahinjana, Soanjana), Meha azedarac (vern. Spines of Zizyphus and Acacia are modified stipules. Some of the important types of modification of leaves are listed below: Tendrils are thread-like sensitive structures which can coil around a support to help the plant in climbing. They are two small lateral outgrowths of the leaf base which protect the young leaf and its axillary bud in the young state. What are the three important components of biodiversity? The leaf with ligule is called ligulate. 5.61 F) are greatly elongated to function like the tendrils. Usually do not have stomata in the region of a stem that differ from the- rest,,! Found at the boundary between the two surfaces are equally leaf characteristics of life ( Gk whorl generally with. 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