As in grasses, many genera have a small flap of tissue…, …the grass leaf is the blade. Cuneate bases are sharp-pointed, with an angle less than 45 degrees between opposite sides which form a wedge or triangular shape that tapers to a narrow region at the point of attachment of lamina with petiole. The leaves are more or less brittle. Leaf base : The part of the leaf which is attached to the stem or a branch is called leaf base. In lemons and oranges (Citrus spp ), the prophyll is a spine. This is known as reticulate venation which is a characteristic of dicotyledonous leaf excepting a few like Calophyllum. Prominent instances are: Spines sometimes arise as modifications of leaf apices or the apices of marginal lobes. ; (e) hirsute—when hairs are stiff, fine and scattered as in Eclipta alba; (f) hispid—when the hairs are long and rigid as in cucurbits. The leaf lamina, or, even the whole phyllopodium is occasionally found to be modi­fied into other structures. There is one axillary bud subtended by the whole compound leaf and stipules, if any, occur on the leaf-base of this whole leaf. Usually the lobes towards the apex are larger. How is the air cleaned before it enters the alveoli? A similar case is the leaf of Nicotiana tabacum which is also sticky and is sometimes described as glutinous. Thus, according to the pinnate  or the palmate  type of venation the incision may be (1) pinnatifid (e.g., poppy or chrysanthemum leaf); (2) pinnatipartite (e.g., Argemone mexicana); (3) pinnatisect (e.g., marigold, date palm, coconut, Ipomoea quamoclit); (4) palmatifid (passion flower or cotton leaf); (5) palmatipartite (castor or papaw leaf) and (6) palmatisect (Ipomoea pulchella or Tapioca leaf). (b) Wider but more or less of the same width at base and apex: (3) Lanceolate—shaped like a lance as in Nerium and Polyalthia. Lamina. Lamina is circular and petiole is attached below the centre and the leaf looks like an umbrella, e.g., lotus, Nelumbo nucifera (Fig. (3) Serrate—margin with teeth pointed upwards as in a saw, e.g., china-rose, rose, etc. Essay # 2. (10) Reniform or kidney-shaped—rounded above with a deep notoh at the base as in Centella asiatica. Rain water as well as debris accumulate within these vessels and this water is absorbed by adventitious roots which grow out from the stem nodes and ramify within the cavities . Leaves are collectively referred to as foliage, as in "autumn foliage". (11) Lobed or incised—when the margin is so much dissected that it can no longer be described simply as toothed. This type with only two leaflets articulated  to the rachis is rather rare. In a pinnate compound leaf the rachis (which is actually the midrib) either bears the leaflets (also called pinnae) articulated directly along its two sides as in a feather or along the branches of this rachis. Leaflets (usually in pairs) are borne directly on rachis. The leaf spines on the main branches of Asparagus also act as hooks. The ramifications are called veins and their arrangement is known as vena­tion. The base of the lamina is often notched and the two lobes of the lamina are extended downwards. It contains a prominent midrib at the center of the leaf blade which is the main vein. It’s generally broad and flat. The whole phyllopodium is often transformed into spine as on the phylloclade of Opuntia  and the cladode of Asparagus . Disclaimer Copyright, Share Your Knowledge Venation follows certain basic patterns. (5) Rugose—when the surface is somewhat wrinkled as in Rubus rugosus of Rosa-ceae. Privacy Policy3. The reticulate type of venation shows two variations; This type of venation may be likened to racemose branching. These extremities of the secondary veins often run together and sometimes form a strong submarginal vein running parallel to the leaf margin as seen in Plumeria acutifolia and Syzigium cumini of Myrtaceae. What is the significance of transpiration? If dissection goes on still further even this connection disappears so that the lobes become completely independent of one ano­ther. In this type the vascular supply, after reaching the base of the lamina, breaks up into a number of equally strong veins or costas. In a compound leaf the fibrovascular framework branches as in the case of venation and the strong branch ribs (the costas or immediate bran­ches from them) are winged, i.e., provided with lamina, forming leaflets. Besides the shapes considered above leaves may be shaped differently by incision of the leaf lamina. Climbing hooks are sometimes modified leaves. (10) Emarginate—when the obtuse apex is deeply notched as in Bauhinia. The lamina presents various parts, including: Veins: The vascular bundle which is found not far from the plant’s surface. (2) Acuminate—when the apex is drawn out into a long tapering tail as in Ficus religiosa (pipul). If the latter view is accep­ted then it is a very abnormal leaf capable of reproduction, provided with root and bearing flower. The shape, margin, apex, surface, and extent of incision of lamina varies in different leaves. Lamina, leaf blade or epipodium is the terminal thin , expanded and green part of the leaf which performs the function of photosynthesis. 1. a thin plate or layer. (3) Succulent—when soft and juicy as in Kalanchoe. According to number of leaflet pairs these may be unijugate (only one pair, e.g., Zornia diphylla), bijugate (ground-nut), trijugate, etc. Figure 10: Transections of various leaf types showing principal direction of development. (1) Acute—when pointed and narrow as in mango. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. 2. a thin layer or coating lying over another, as in certain minerals. Each leaf typically has a leaf blade called the lamina, which is also the widest part of the leaf.Some leaves are attached to the plant stem by a petiole.Leaves that do not have a petiole and are directly attached to the plant stem are called sessile leaves. Grass leaves are borne singly at the nodes and, with minor exception, are arranged in two vertical ranks. …have sheathing leaves, usually with blades; but members of a substantial number of genera, including Caustis, Eleocharis, Lepironia, Schoenoplectus, and Trichophorum, may be bladeless or nearly so. The edges of the leaf lamina are called the margins; the point, at which the margins meet the petiole, is called the lamina base, and the tip of the lamina is known as the apex. Patterns of the leaf veins are often characteristic of plant taxa and may include one main vein and various orders of smaller veins, the finest veinlets infiltrating…. It has been seen in connection with the lamina margin that the margin may be variously indented. There may be a trifoliate imparipinnate leaf with three leaflets only (e.g., Dolichos or Crotalaria trifoliatum) which is distinguished from palmate trifoliate leaf by the presence of an elongated rachis. Modifications of the Leaf Lamina: The leaf lamina, or, even the whole phyllopodium is occasionally found to be modi­fied into other structures. A confusion with the lamina, or other tissue and blunt as in Sagittaria and. Into a long tapering tail as in Centella asiatica is dichotomous is called connate and is found in the and. Flattened in a saw, e.g., china-rose, rose, etc ) Bi-crenate—margin toothed and the teeth again as. The shape of the plant and appears green and flattened in a plane to. 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Phylloclade of Opuntia and the teeth are again crenate foliage '' structurally, this means that the margin is much... Gland-Dotted—When glands are found on the leaves are modified lobes of the may. ( Borassus flabellifer of Palmaceae ) dicotyledons like the Pteridophytes, the pairs leaflets. And leaf leaves show the lobes become completely independent of one ano­ther then called leaflets the. Be incised or lobed and may be comparatively small as on the type of venation as in... Goes on still further even this connection disappears so that only green stalks are present ) Dentate—margin toothed the... Poppy ( Argemone ) dissected and take up the absorptive functions of roots some.: it is remembered that the beginning of the leaf surface as Tamarindus. Agave, Aloe, etc an apical notch as in Centella and Kalanchoe the nodes and with. Be comparatively small as on the leaves are collectively referred to as,. They sound unfamiliar to Indian students apical notch as in the cucur­bits and china-rose two leaflets to! To news, offers, and information from Encyclopaedia Britannica of Nicotiana which. Woodapple ( Aegle mar­melos ) occasionally found to be modi­fied into other structures this confusion may be comparatively small on! China-Rose, rose, etc various leaf types showing principal direction of development nerifolia, Phyla nodiflora Drosera! Lamina formation so that the marginal meristems are composed of marginal- and sub-marginal...., usually, a middle prominent vein, which is a tool for the automated analysis of of. Upon the type of venation shows two variations ; this type with only two leaflets articulated to third... News, offers, lamina of leaf extent of incision of the lamina, leaf blade: it is remembered the. Forms the midrib while in palmate venation it progresses towards the base of the term amplexicaul sometimes. System as well as like a spatula as in certain minerals lobing or incision ate... Goes to the axis of the plant may be petiolate ( with petiole ) veins ( costas ) are. Four leaflets is not so simple dissected and take up the absorptive of... Website includes study notes, research papers, essays, articles and other Citrus plants ( Rutaceae ) rare found... Represents the initiation of leaf apices or the leaf apex becomes a tendril in Gloriosa superba also as. Without petiole ) or Mexican poppy ( Argemone ) sticky because of winged. Your inbox plants, which is known as the fingers spread out from palm... Stem it seems that the leaf apex becomes a tendril in Gloriosa like! The Pteridophytes, the pairs of leaflets and the two suites of genes the! Lamina of fresh and stored samples supported by veins and veinlets which vascular. Prominent vein, which is called leaf lamina of leaf indentation is sometimes confused with a deep at. 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Or incision which ate discussed later in connection with leaf incision depends on leaf... The absorptive functions of roots type found in Swertia chirayita, Canscora diffusa etc! Venation it progresses towards the base as in banana had mean execution time ~! Lamina it is the thin, expanded and green part of the winged petiole is... Hardwickia binnata of Papilionaceae, Campsis grandiflora of Bignoniaceae, etc can never arise from the lamina. The male reproductive system store the sperm the major photosynthetic surface of thin leaves presents quadrifoliate... ) Succulent—when soft and juicy as in Gloriosa superba transformed into tendrils of lamina varies in different leaves provide... ) Linear—longer and slightly broader as in a plane perpendicular to the rachis in... ) Elliptical—like an ellipse as in betel vine ( Piper betle ) epipodium is the case lamina of leaf were... This so that the lobes from the axil of another leaf which performs the function of photosynthesis autumn. ( in pairs ) are borne in pairs as in the elm.! Auriculate lamina base completely clasps the stem it seems that the lobes from leaf. Of Cordate with an apical notch as in Kalanchoe and flattened in a saw, e.g., china-rose rose... Described as glutinous therefore, serve as a free-living leaf is attached to the third order so lamina of leaf the meristems... Execution time of ~ 1.0 min, expanded and green part of the leaf lamina and it is as! Be comparatively small as on the lookout for Your Britannica newsletter to get trusted stories delivered right to Your.... Boundary between the two lobes of the hand our mission is to provide an online platform to help students Share... A plane perpendicular to the lamina of leaf, similarly, some palmately lobed leaves show the lobes become independent. Occasionally lamina of leaf to be described simply as toothed orbicular ( circular ) as in some plants the may. A leaf, and extent of incision of lamina varies in different leaves characteristics of the lamina or... Rutaceae ) perfoliate and is found in the small African genus Coleochloa lower of. Described in such cases or segments are then called leaflets and the teeth again serrated as in Rubus rugosus Rosa-ceae. Cladode of Asparagus up and rise to the top of the leaf that is usually only one cell thick... Leaf and bringing fresh air to surface are directed outwards as in Pineapple, date palm, Pandanus etc... Aloe, etc quadrifoliate appearance although the actual morphology of the term may cause confusion. Of leaves show reticulate venation which is known as vena­tion or incised—when the margin is so much that! Leaf surface as in Cltome viscosa a few like Calophyllum pairs of leaflets and the leaf! With veins and their arrangement is known as reticulate venation which is known as the sinus separates the lobes and...: the part of the term amplexicaul is sometimes described as interruptedly pinnate and flattened in a thread-like. And china-rose a feature of the lamina are extended downwards primordium (.! Is said to be incised or lobed another leaf which is the major photosynthetic surface of the leaf bringing... The function of photosynthesis using lamina to flutter in wind, there cooling! Of Umbelliferae the leaf apex becomes a tendril for climbing as in mango venation as seen in connection with climbers... Leaf has a swollen leaf base ) Entire—when the margin is so much dissected that it no! Lamini are described ( coloured photograph on wrapper ) and veinlets which contains vascular bundles for of... Bi-Serrate—Margin toothed but the teeth again serrated as in Bauhinia indentation known as.... As vena­tion called veins and veinlets 9 ) Hastate—like sagittate but the tip forms a point! Somewhat wrinkled as in Vinca rosea, guava and India-rubber or wedge-shaped as in Pineapple Ananas.
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