types of leaf venation

When there are more than two leaves at each node which are arranged in a circle or a whorl. E.g., Rose. E.g., bay leaf (Cinnamomum), Indian plum (Zizyphus). Venation in Leaves 2. If the leaflets are odd in number then it is said to be imparipinnate. In some plants the petiole of the leaf or a part of the rachis gets modified into flattened or winged leaf like structure called as a phyllode. E.g., gourd, castor, China rose. Calotropis, 3.Ternate Phyllotaxy : In this type there are three leaves attached at each node eg. Pinnately  compound leaves 2. When the veins are irregularly distributed to form a channel, it is known as Reticulate Venation. The veins are chiefly made of vascular tissues, the xylem and phloem. 4. Stipules 4. There are three principal types of phyllotaxy: Here a single leaf is produced at each node alternately on the stem. The leaf base is expanded to form a laminar structure to carry out photosynthesis. When the tertiary rachii are further branched i.e., more than thrice pinnate. Simple Leaf: A leaf is said to be simple in which the leaf blade or lamina is entire. If the rachis is branched once and the leaflets arise on the secondary rachii the leaf is said to be bipinnate. This gives off lateral veins which reach the margin or apex of the leaf. E.g., gourd, castor, China rose. When the veins spread upward in a curved manner and converge towards the apex. In grass they converge at the apex and hence it is called convergent. Under ground modifications, Parts of a Leaf : 1. E.g., Caesalpinia. A leaf is said to be simple when it consists of a single blade which may be entire or incised (and, therefore, lobed) to any depth, but not cut down to the mid-rib or the petiole. The leaf apex is modified into a lid. E.g., drumstick (Moringa). Decompound. It is the characteristic feature seen in dicots. 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. Copyright © 2018-2021 BrainKart.com; All Rights Reserved. Hence it is called divergent. E.g., Mango, guava, banyan, papaya etc. Types of Leaves 3. According to the number of leaflets present the compound leaf may be 1. unifoliate (eg. E.g., Ixora, Mussaenda. When five or more leaflets are joined to the tip of the petiole and are spreading like fingers from the palm. Tripinnate 4. Pinnate Venation: The veins extend from the midrib to the leaf margin. The arrangement of veins in the leaf blade or lamina is called, In this type, there is a prominent midrib in, : In this type the leaves are arranged alternatively in, : In this type of arrangement two leaves are present, : The pairs of leaves arranged in successive nodes. 2. Such a leaf is said to be decompound. In this type of venation, the veins and veinlets run parallel to each other. Bifoliate (eg.Zornia diphylla) 3. Lemon) 2. The pinnately compound leaf may be of the type 1. A pair of leaves at one node stands directly over the lower pair in the same plane. 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. A leaf with three leaflets articulated to the tip of the petiole. a. Pinnateley Parallel venation : In this type, there is a prominent midrib in the centre. (ii) Convergent Type: When the veins spread upward in a curved manner and converge towards the apex. Dichotomously branched veins. These stipules are situated between petiole and axis. There is only one leaf at each node. Parallel Venation: In this type of venation all the veins run parallel to each other. Trifoliate (eg. E.g., Grasses, wheat, bamboo. Pinnately compound leaves are of the following types: When the rachis of a pinnately compound leaf bears the leaflets, it is said to be unipinnate. E.g., rangoon creeper (Quisqualis). The two types of compound leaf are: 1. There are two types of palmately reticulate venation: (i) Divergent Type: When the main veins diverge towards the margin of the leaf. Neem .When the number of leaflets is even it is said to be paripinnate eg. It is mainly of two types namely Reticulate venation andParallel venation . The purpose of phyllotaxy is to avoid overcrowding of leaves so as to expose the leaves maximum to the sunlight for photosynthesis. E.g., sweet pea (Lathyrus), pea (Pisum). E.g., bay leaf (Cinnamomum), Indian plum (Zizyphus). 2.Bipinnate: In this type of compound leaves, the primary rachis is branched to produce secondary rachis which bear the leaflets. e.g.Mango. In the pitcher plant Nepenthes, a terrestrial insectivorous plant, the lamina gets modified into a pitcher-like structure. Each scale leaf contains an axillary bud in its axil. According to the number of leaflets present the compound leaf may be 1. Also known as forked venation. R e t i c u l a t e Venation: This type of venation is common in all dicot leaves. It is mainly of two types namely Reticulate venation and Parallel venation 1. These are free from one another, that is, not connected by any lamina, and more or less distinctly joined (articulated) at their base. Moringa, 4.Decompound : When the compound leaf is more than thrice pinnate it is said to be decompound. E.g., Ficus, Magnolia. Eg. From this arise many veins perpendicularly and run parallel to each other eg. Petiole 3. Leaves with stipules are called stipulate and those without are called exstipulate. The arrangement and distribution of veins and veinlets on the lamina of a leaf is called venation. It is of two types. Modifications. E.g., rose, pea. The arrangement of veins and the veinlets in the lamina is known as venation. A leaf which bears a number of leaflets which seem to be radiating from a common point on the tip of the petiole. Banana. Bipinnate 3. Reticulate venation is divided into two types depending upon the number of the principle veins. Terms of Service Privacy Policy Contact Us, Notes on Botany for School and College Students, Copyright infringement takedown notification policy, Copyright infringement takedown notification template, Types of Pollination (With Diagram) | Flowering Plants | Botany. E.g., Australian acacia. E.g., silk cotton tree (Bombax). A number of more or less equally strong veins proceed from the leaf base and converge towards the leaf apex. Coriander Palmately compound leaf, When all the leaflets are attached at a common point at the tip of the petiole, it is known as palmately compound leaf. 3.Tripinnate: In this type the secondary rachis produces the tertiary rachis which bear the leaflets eg. In this article we will discuss about:- 1. Multifoliate (eg. Lamina, Inflorescence : Racemose, Cymose, Mixed and Special types, FLOWER - A Metamorphosed Shoot : Evidences to support that flower is a modified shoot, Types of Placentation : Axile,Marginal, Parietal, Basal, Superficial Placentation, Plant Aestivation And Types of Aestivation. (2) Parallel Venation: It is the characteristic feature seen in dicots. In some plants, the entire leaf is modified into a tendril. The leaflets are borne on a common axis and they do not bear any axillary buds in their axils. The arrangement and distribution of veins and veinlets on the lamina of a leaf is called venation. Email me at this address if a comment is added after mine: Email me if a comment is added after mine. There are two types of palmately reticulate venation: When the main veins diverge towards the margin of the leaf. In Utricularia which is an aquatic insectivorous plant, segments of the leaf modify into bladder like structures which trap small insects present in the water. Dicotyledons, or plants with two seed leaves, are reticulate-veined. When the stipules are large and green leafy structures. E.g., Michelia champaca. A pair of leaves at one node stands at right angles to the next upper or lower pair.

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