Modifications. 4. eg. In this type two stipules lie between the petioles of opposite or whorled leaves. 1.Unipinnate: In this type the pinnae are borne directly on the rachis. E.g., Rose. In Gloriosa superba the leaf apex is modified into a tendril. According to the number of leaflets present the compound leaf may be 1. unifoliate (eg. Venation in Leaves 2. A leaf with four leaflets articulated to the tip of the petiole. The arrangement of veins in the leaf blade or lamina is called venation. On the basis of their structure and relation to the leaf, stipules may be of the following types: The two stipules are free and are borne on the two sides of the leaf base. Two types of venation are reticulate venation and parallel venation. E.g., Murraya. The veins are chiefly made of vascular tissues, the xylem and phloem. Decompound. Copyright © 2018-2021 BrainKart.com; All Rights Reserved. These are free from one another, that is, not connected by any lamina, and more or less distinctly joined (articulated) at their base. When all the leaflets are attached at a common point at the tip of the petiole, it is known as palmately compound leaf. The leaflets are known as the pinnae. In Borassus (Palmyra) all the main veins spread out towards the periphery. E.g., rose. eg. Tripinnate 4. E.g., Opuntia. It may be with incision or without incision. It is a leaf in which the secondary rachii are branched to form tertiary rachii which in turn bear the leaflets. Here stipules are modified into spines. In the pitcher plant Nepenthes, a terrestrial insectivorous plant, the lamina gets modified into a pitcher-like structure. Leaf blades are categorized by type using dozens of different attributes. A pair of leaves at one node stands directly over the lower pair in the same plane. Leaves are collectively referred to as foliage, as in "autumn foliage". These stipules are situated between petiole and axis. The two types of palmate reticulate venation are . (BS) Developed by Therithal info, Chennai. In this type there are a number of more or less equally prominent veins which arise from the tip of the petiole and reach outwards or upwards. When the number of leaflets is odd, it is said to beimparipinnate eg. Reticulate Venation: When the veins are irregularly distributed to form a channel, it is known as Reticulate Venation. Compound leaf: Here the lamina is divided in to a number of leaf like lobes called the leaflets. Pinnate leaves: There is a main nerve, called midrib, from which the other nerves derive, remembering a plume. The leaflets are borne on a common axis and they do not bear any axillary buds in their axils. eg.Polyalthia. When five or more leaflets are joined to the tip of the petiole and are spreading like fingers from the palm. Divergent -palmyra.All the veins starts from the base but they diverge lateral margin of the leaf The type of venation where veins are arranged parallel to one another and occur mostly in monocots. There are two types of palmately reticulate venation: When the main veins diverge towards the margin of the leaf. The petiole is modified into a tendril to hold the pitcher upright. Oak and cherry are examples. a. Pinnateley Parallel venation : In this type, there is a prominent midrib in the centre. Petioles, stipules, veins, and a midrib are all essential structures of a leaf. E.g., sweet pea (Lathyrus), pea (Pisum). Types of Root System And Functions of roots, Root Modifications for Taproot, adventitious roots, Characteristic features and Functions of the stem, Modifications of stem : 1. According to the number of leaflets present the compound leaf may be 1. The leaf base in many plants is associated with two minute appendages called stipules. Veins provide mechanical strength to the leaf. E.g., Mango, guava, banyan, papaya etc. E.g., Hibiscus, mustard. They are of three types: 1. It is of two types. According to the arrangement along the stem When the stipules fall off soon after the leaf unfolds, they are called deciduous. Superficial veins are closer to the skin’s surface. E.g., Australian acacia. The fantastic looking foliage of this cultivar has … Veins are important structures of the plant leaf. With palmate venation, all the veins radiate fan-like from a single point at the leaf’s base. A bud (axillary bud) is present in the axil of a simple or a compound leaf, but it is leaf never present in the axil of the leaflet of a compound leaf. Sub aerial modifications 3. Mango. Parallel-veined leaves: the veins run at the same distance to each other, like in canes. E.g., gourd, castor, China rose. Calotropis, 3.Ternate Phyllotaxy : In this type there are three leaves attached at each node eg. The short-shoot leaves are orb-shaped and have cordate bases, while the long-shoot leaves are ovate and have rounded bases. Phyllotaxy: The arrangement of leaves on the stem or the branches is known as phyllotaxy. Palmately compound leaves are of the following types: A single leaflet is articulated to the petiole. Buy or borrow a field guide that focuses on plants in … Venation in Leaves 2. Venation in Leaves: The arrangement of veins and the veinlets in the lamina is known as venation. E.g., peepul (Ficus), mango (Mangifera). Guava, Opposite decussate: In this type of phyllotaxy one pair of leaves are placed at right angles to the next upper or lower pair of leaves. Once you have narrowed down the type of leaf, you … They are crucial to gathering energy, respiration and protection. Continue reading to learn more … Some patterns in tree leaf venation include the following: Pinnate veins branch out in opposite directions from the central vein that runs the length of the leaf Leaf Venation. Nerium. According to the pattern of arrangement veins are of two types; parallel venation and reticulate venation. In this type of venation there is a prominent vein called the midrib from which arise many small veins which finally form a net like structure in the lamina. Stipules 4. E.g., Ixora, Mussaenda. When only a single blade is inserted directly on the petiole, the leaf is called simple. When a plant’s foliage creates insufficient chlorophyll, the leaves become pale or begin to yellow. Bipinnately compound leaves extend from secondary veins that connect to the main vein. Bipinnate 3. This gives off lateral veins which reach the margin or apex of the leaf. E.g., Palmyra palm. In some plants, the entire leaf is modified into a tendril. From the presence of midveins, parallel venation is divided into two more types: Pinnate parallel venation – In this, the veins arise from the prominent midvein (midrib) present in the center of the leaf lamina from base to the apex. A unipinnate leaf is said to be paripinnate if the leaflets are even in number. Systemic veins return oxygen-depleted blood from the rest of the body to the right atrium of the heart. 3.Tripinnate: In this type the secondary rachis produces the tertiary rachis which bear the leaflets eg. bi-pinnate compound leaf A leaf that is sub-divided in smaller "compound leaflets", arranged in pairs opposite from each other on the stem. In this type of venation, the veins and veinlets are repeatedly branched and irregularly distributed, forming a complex network, e.g., dicotyledonous leaves. Small veins or capillaries branch out from the midvein to form intricate patterns in the leaf structure. The pattern in arrangement of veins in the blade of a leaf is called as venation. e.g.Mango. The lamina is the most important part of the leaf since this … The veins arise from the tip of the petiole, diverge and reach the margin of the leaf-blade in a more or less parallel manner. The entire leaf or a part of a leaf may be modified into a pointed structure called a spine. Phyllotaxy 5. Leaves are one of the most important plant parts. E.g., Zizyphus. R e t i c u l a t e Venation: This type of venation is common in all dicot leaves. Simple Leaf: A leaf is said to be simple in which the leaf blade or lamina is entire. This helps in describing the plant and in enjoying its beauty. They involve in the transportation of food produced in the leaf by photosynthesis and transportation of water into the leaf. Trifoliate (eg. Neem .When the number of leaflets is even it is said to be paripinnate eg. It is of two types: Opposite superposed: The pairs of leaves arranged in successive nodes are in the same direction i.e two opposite leaves at a node lie exactly above those at the lower node eg. These stipules form a hollow tube around the internodes up to a certain height. Monocots and dicots differ in their patterns of venation. E.g., Grasses, wheat, bamboo. The purpose of phyllotaxy is to avoid overcrowding of leaves so as to expose the leaves maximum to the sunlight for photosynthesis. A strong vein, known as the midrib, runs centrally through the leaf- blade from its base to the apex; this produces thinner lateral veins which in their turn give rise to still thinner veins or veinlets. Each scale leaf contains an axillary bud in its axil. When the stipules are large and green leafy structures. There is only one leaf at each node. Generally, there are two types of venation: Carolyn Whorton. Venation. Often veins follow the shape of the leaf. There are four types of veins: Deep veins are located within muscle tissue. Diversity in leaf vein systems, emphasizing leaf vein diameters, numbers of vein orders, vein length per unit area (VLA), free‐ending veins (FEVs), xylem conduit sizes, accessory transport tissues and bundle sheath extensions. 1.Alternate phyllotaxy: In this type the leaves are arranged alternatively in the nodes.
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