Learn why leaves of deciduous trees change colour in autumn. In descriptions of a single leaf, the neuter singular ending of the adjective is used, e.g. Leaf Arrangement (Phyllotaxy) Three different leaf arrangements: Alternate (one leaf per node), opposite (two leaves per node) and whorled (three or more leaves per node). The term leaf refers to the organ that forms the main lateral appendage on the stem of vascular plants. Corrections? Tapering and ending in a short, slender point. It is highly recommended for planting in urban and suburban areas. Leaf margins of simple leaves may be lobed in one of two patterns, pinnate or palmate. The Description of Leaves, University of Rochester, https://en.wikipedia.org/w/index.php?title=Glossary_of_leaf_morphology&oldid=982175207, Short description with empty Wikidata description, Creative Commons Attribution-ShareAlike License, Having two leaflets, each leaflet being bifoliolate, With three components, each with three leaflets, Consisting of leaflets all radiating from one point, Having two rows of leaflets on opposite sides of a central axis, see, Leaf blade in one continuous section, without leaflets (not compound), Pinnately compound in which each leaflet is itself bipinnate. They are attached by a continuous vascular system to the rest of the plant so that free exchange of nutrients, water, and end products of photosynthesis (oxygen and carbohydrates in particular) can be carried to its various parts. Shaped like a sword, long and narrow with a sharp pointed tip. In the spring, trees grow new leaves. The epidermis also secretes a waxy substance called the cuticle. In general, leaves are thin, flat organs responsible for the photosynthesis of the plant. As much as one-fifth of the mesophyll is composed of chlorophyll-containing chloroplasts, which absorb sunlight and, in conjunction with certain enzymes, use the radiant energy in decomposing water into its elements, hydrogen and oxygen. The most common form of storage leaves are the succulent leaf bases of underground bulbs (e.g., tulip and Crocus) that serve as either water- or food-storage organs or both. A leaf that has only one blade is called a simple leaf. Many desert plants, such as Lithops and aloe, develop succulent leaves for water storage. Although photosynthesis typically only occurs on the upper surface of the leaf, it can occur on both sides in some plant species. Typically, a leaf consists of a broad expanded blade (the lamina), attached to the plant stem by a stalklike petiole. Crenulate margins have rounded teeth or scalloped margins. Doubly Pinately Compound . As the primary sites of photosynthesis, leaves manufacture food for plants, which in turn ultimately nourish and sustain all land animals. Also used to describe compound leaves with finger-like leaflets. The leaf may also be reduced to a spine or scale. Leaves are collectively referred to as foliage, as in "autumn foliage". Botanically, leaves are an integral part of the stem system. Sugars provide the energy that makes plants grow. Learn more about succulent plants. 4.13). Another problem is to establish definitions that meet all cases or satisfy all authorities and readers. A round leaf where the petiole attaches near the center. Most leaves have a broad, flat part called a blade. The hydrogen obtained from water is combined with carbon dioxide in the enzymatic processes of photosynthesis to form the sugars that are the basis of both plant and animal life. Leaf, in botany, any usually flattened green outgrowth from the stem of a vascular plant. A leaf is often flat, so it absorbs the most light, and thin, so that the sunlight can get to the chloroplasts in the cells. Botanical terms that describe the surfaces of leaves and stems: Glaucous: Covered with a whitish powder or waxy coating. In many epiphytic bromeliads, the pseudotrunk also functions as a water reservoir. Pointed, having a short sharp apex angled less than 90°. The thin âleafyâ portion on either side of the midrib is â¦ Having lobes with incisions that extend over half-way toward the petiole. Among â¦ The margins of simple leaves may be entire and smooth or they may be lobed in various ways. Mango, Cucurbita, Guava etc., are the examples of simple entire leaves (Fig. With a single leaflet. See more. Reversed trullate, the longer sides meet at the base rather than the apex. The area between the nodes is called the internode. A node is the place where one or more leaves are attached along the stem. The central one is called the midrib or midvein. Tendrils and hooks are the most common of these modifications. In the water hyacinth (Eichhornia crassipes), swollen petioles keep the plant afloat. Definition of a Leaf: The leaf is a flattened, lateral outgrowth of the stem in the branch, developing from a node and having a bud in its axil. Articles from Britannica Encyclopedias for elementary and high school students. Having lobes pinnately arranged on the central axis. And if you need a more comprehensive collection of leaf types, make sure to check out The Book of Leaves: A Leaf-by-Leaf Guide to Six Hundred of the Worldâs Great Trees. Learn how the structure of leaves affects their functions in this video. These layers protect the leaf from insects, bacteria, and other pests. For example, it seems altogether reasonable to define a mucro as "a small sharp point as a continuation of the midrib", but it may not be clear how small is small enough, how sharp is sharp enough, how hard the point must be, and what to call the point when one cannot tell whether the leaf has a midrib at all. Leaves may also be folded or rolled in various ways. Palmately Compound . Examples include various bulbous plants such as Boophone. For more terms describing other aspects of leaves besides their overall morphology see the leaf article. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). Definition of a Leaf 2. Similar terms are used for other plant parts, such as petals, tepals, and bracts. Asymmetrical leaf base, with one side lower than the other. Every hibiscus leaf's shape is predetermined and established in the seed embryo. The central leaf, or mesophyll, consists of soft-walled, unspecialized cells of the type known as parenchyma. Leaf Composition Simple Leaf . Various technical terms are used for describing the form and arrangement of flowers. The following is a defined list of terms which are used to describe leaf morphology in the description and taxonomy of plants. When only a single blade is inserted directly on the petiole, the leaf is called simple. In catbrier (Smilax), the stipules function as tendrils. Glands in the leaves secrete enzymes that digest the captured insects, and the leaves then absorb the nitrogenous compounds (amino acids) and other products of digestion. leaf your worries behind; leaves abound from all around; leaves are falling, autumn is calling; leaves of red and gold; leaves will fall in fall; lovely leaves; oh my gourd! These are grouped below as follows: ... A leaf-like element below a flower or on an inflorescence. Discover the 2020 Nissan LEAF: The best-selling Electric Vehicle of all time. Chlorophyll production in deciduous plants slows as the days get shorter and cooler, and eventually the pigment is broken down completely. A compound leaf has two or more blades attached to the petiole. Lacerate or lobed leaf margins are characterized by their rounded lobed edges, like little ear lobes which go around the leaf margins. Certain organs that are superficially very different from the usual green leaf are formed in the same manner and are actually modified leaves; among these are the sharp spines of cacti, the needles of pines and other conifers, and the scales of an asparagus stalk or a lily bulb. folium lanceolatum 'lanceolate leaf', folium lineare 'linear leaf'. Botanical name: Quercus â¦ Some succulents, such as cacti, store water only in the stem and commonly lack leaves. Opposite leaf patterns occur when the leaves join at the node in pairs. The internal structure of the leaf is protected by the leaf epidermis, which is continuous with the stem epidermis. The terms listed here all are supported by technical and professional usage, but they cannot be represented as mandatory or undebatable; readers must use their judgement. Most leaves have a stem (or petiole) that attaches the leaf to the rest of the plant. Leaf. Leaves attached to stem in pairs that stand opposite each other. A leaf (plural leaves) is the principal lateral appendage of the vascular plant stem, usually borne above ground and specialized for photosynthesis. A leaf is a plant organ and is made up of a collection of tissues in a regular organisation. Various authors or field workers might come to incompatible conclusions, or might try to compromise by qualifying terms so vaguely that a description of a particular plant practically loses its value. In flowering plants, as well as the blade of the leaf, there may be a petiole and stipules; compound leaves may have a rachis supporting the leaflets. With the blade shape different on each side of the midrib. Authors often use terms arbitrarily, or coin them to taste, possibly in ignorance of established terms, and it is not always clear whether because of ignorance, or personal preference, or because usages change with time or context, or because of variation between specimens, even specimens from the same plant. Cotyledon definition, the primary or rudimentary leaf of the embryo of seed plants. After reading this article you will learn about: 1. As a result, a zone of cells across the petiole becomes softened until the leaf falls. Chlorophyll, the substance that gives plants their characteristic green colour, absorbs light energy. Examples include, but are not limited to, Viburnums, Olive trees, Maple trees, Fringe trees, and Ash tree leaves. The main function of a leaf is to produce food for the plant by photosynthesis. Let us learn about Diversity in the Leaf. Teardrop-shaped, stem attaches to the tapering end; reversed ovate. Donât forget to bookmark the entire slideshow of all 76 leaves (there are too many to fit into one post!). Leaves may be simple, with a single leaf blade, or compound, with several leaflets. Botanically, leaves are an integral part of the stem system. A compound leaf is one whose blade has two or more sub-units called leaflets attached to the same stalk or petiole. A tree leaf has several types of veins. Oval, egg-shaped, with a tapering point and the widest portion near the petiole. Classification of trees with these types of leaves can further be defined by whether the leaves and leaflets all start from the same point, which can help in identifying the specific genus of a tree based on its leaves, bark, and seeds. Each leaf typically has a leaf blade (lamina), stipules, a midrib, and a margin. When fully formed, it resembles a heart, which is why horticulturists refer to the hibiscus leaf â¦ Tapering to a long point in a concave manner. Having an elongated form with slightly parallel sides, roughly rectangular. A leaf is part of a plant that's usually green and attached to it by a stem or stalk. Palm-shaped, i.e., with lobes or leaflets stemming from the leaf base. Leaves are the original solar panels, capturing energy from sunlight in a biochemical process called photosynthesis. The cells within leaf tissues are hectic with biochemistry, importing water and nutrients to support their frantic work, and exporting sugar to provide energy to the remainder of the plant. The Description of Flowers. The major tissue systems present are: 1. First, there is the blade. Compound Leaf . Whorled: show all. Some leaves have a petiole, which attaches the leaf to the stem; leaves that do not have petioles are directly attached to the plant stem and are called sessile leaves. Whole leaves or parts of leaves are often modified for special functions, such as for climbing and substrate attachment, storage, protection against predation or climatic conditions, or trapping and digesting insect prey. Spines are also modified leaves. The import/export business conducted by the leaves is supported by xylem and phloem pipelines, which explains why leaves are so richly veined. Veins also carry the products of photosynthesis back to the rest of the tree. Having lobes with incisions that extend almost up, but not quite to the petiole. There are some indications that day length may control leaf senescence in deciduous trees through its effect on hormone metabolism; both gibberellins and auxins have been shown to retard leaf fall and to preserve the greenness of leaves under the short-day conditions of autumn. Pigments other than chlorophyll give this maple leaf its autumn colours. Having lobes with incisions that extend more than half-way toward the midrib. Spoon-shaped; having a broad flat end which tapers to the base, Somewhat blunted, neither blunt nor sharp. The edge of the leaf may be regular or irregular, may be smooth or bearing hair, bristles or spines. The first year is spent growing leaves, stems and roots. Pinnately Compound . The arrangement of veins (the vascular tissue) folia linearia 'linear leaves'. Being divided by clefts, may be pinnately lobed or palmately lobed. Carnivorous plants use their highly modified leaves to attract and trap insects. Leaf structure is described by several terms that include: Being one of the more visible features, leaf shape is commonly used for plant identification. The epidermisthat covers the upper and lower surfaces 2. Carnelian is an alteration of cornelian that is based on Latin carn-, meaning "flesh," in reference to the flesh-red color that some perceive in the mineral. Abscission layers may also form when leaves are seriously damaged by insects, disease, or drought. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Triangular, wedge-shaped, stem attaches to point. Carnelian can be used to describe leaves having a reddish-orange or brownish-red color, like the colors often found in the quartz by that name. For example, whether to call leaves on the same tree "acuminate", "lanceolate", or "linear" could depend on individual judgement, or which part of the tree one collected them from. In the fall, the leaves of many trees turn various bright colors before falling to the ground. These changes in leaf pigments are responsible for the autumn colours of leaves. Types. In some cases, these trees can display a sub-opposite arrangement, where the leaves â¦ Usually, a stalk called a petiole attaches the blade to the plantâs stem. foliis ovatis 'with ovate leaves'.. Updates? With the leaf blade surrounding the stem such that the stem appears to pass through the leaf. : a leaf whose blade is not divided to the midrib even though lobed â compare compound leaf. Veins, which support the lamina and transport materials to and from the leaf tissues, radiate through the lamina from the petiole. In descriptions of multiple leaves, the neuter plural is used, e.g. A healing layer then forms on the stem and closes the wound, leaving the leaf scar, a prominent feature in many winter twigs and an aid in identification. The lobes merge as the leaf matures. An example would be a. Succulent, any plant with thick fleshy tissues adapted to water storage. Others, such as agaves and kalanchoes, store water mainly in the leaves. Circular in cross-section; more or less cylindrical without grooves or ridges. The leaves and stem together form the shoot. Most leaves have stomata, which open and close.They regulate carbon dioxide, oxygen, and water vapour exchange with the atmosphere. The same cautions might apply to "caudate", "cuspidate", and "mucronate", or to "crenate", "dentate", and "serrate". In cacti, spines are wholly transformed leaves that protect the plant from herbivores, radiate heat from the stem during the day, and collect and drip condensed water vapour during the cooler night. In the garden pea (Pisum sativum), the terminal leaflet of the compound leaf develops as a tendril. Viscid (Viscous): Covered with sticky or resinous secretion. The process creates oxygen, which people and other animals breathe. The oak leaf has a lobed leaf margin and can be â¦ Parts of a Leaf 3. Many nonparasitic plants that grow on the surfaces of other plants (epiphytes), such as some of the bromeliads, absorb water through specialized hairs on the surfaces of their leaves. In temperate trees leaves are simply protective bud scales; in the spring when shoot growth is resumed, they often exhibit a complete growth series from bud scales to fully developed leaves. Very deeply lobed, the lobes being very drawn out, often making the leaf look somewhat like a branch or a pitchfork. Plants that use insects as a nitrogen source tend to grow in nitrogen-deficient soils. Yellow and orange pigments called carotenoids become more conspicuous, and, in some species, anthocyanin pigments accumulate. A leaf is the green, flat lateral outgrowth in plants. The mesophyll (also called chlorenchyma) inside the leaf that is rich in chloroplasts 3. Having lobes with incisions that extend almost, or up to midrib. Leaves are attached to the stem singly, ascending either on alternate sides of the stalk, or in a spiraling pattern. Their nervations come from the center of the leaf and often have a serrated base. A leaf is made of many layers that are sandwiched between two layers of tough skin cells (called the epidermis). A great variety of base and apex shapes also are found. Bracts are typically shaped differently than other leaves on the plant. The second year is when the plant bolts upwards producing flowers and going to â¦ The basic angiosperm leaf is composed of a leaf base, two stipules, a petiole, and a blade (lamina)....…, Leaves are the other plant organ that, along with stems, constitutes the shoot of the vascular plant...…, Leaves originate on the flanks of the shoot apex. In many trees leaf senescence is brought about by declining day length and falling temperature toward the end of the growing season. The petiole sometimes extends into the leaf and divides the leaf into two equal halves, and when it does itâs called the midrib. With a sharp, elongated, rigid tip; tipped with a cusp. The leaves are obovate, deciduous and up to 20 cm (7.9 in) long. Terms describing overall arrangement of leaves on the stem. Much longer than wide and with the widest portion near the tip, reversed lanceolate. Leaves are initiated in the apical bud (growing tip of a stem) along with the tissues of the stem itself. A plant that completes its life cycle over 2 years. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. A local concentration of cell divisions marks the very...…. Distichous phyllotaxis, also called "two-ranked leaf arrangement" is a special case of either opposite or alternate leaf arrangement where the leaves on a stem are arranged in two vertical columns on opposite sides of the stem. 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. In pinnately lobed margins the leaf blade (lamina) is indented equally deep along each side of the midrib (as in the white oak, Quercus alba), and in palmately lobed margins the lamina is indented along several major veins (as in the red maple, Acer rubrum). Having ear-shaped appendages reaching beyond the attachment to the petiole or to the stem (in case of a seated leaf). Once emerging from the stem, hibiscus leaf buds take the form of two, round lobes. The Latin word for 'leaf', folium, is neuter. Leaves are, however, quite diverse in size, shape, and various other characteristics, including the nature of the blade margin and the type of venation (arrangement of veins). In ocotillo (Fouquieria splendens), the blade falls off and the petiole remains as a spine. 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 leaflike structures. Having lobes with incisions that extend less than half-way toward the midrib. Opposite: show all. Its main functions are photosynthesis and gas exchange. Scurfy: Covered with small scalelike particles. Many monocotyledons have sheathing leaf bases that are concentrically arranged and form a pseudotrunk, as in banana (Musa). This article was most recently revised and updated by, https://www.britannica.com/science/leaf-plant-anatomy, Palomer College - WAYNE'S WORD - Leaf Terminology, leaf - Children's Encyclopedia (Ages 8-11), leaf - Student Encyclopedia (Ages 11 and up). Having leaf tissue taper down the petiole to a narrow base, always having some leaf material on each side of the petiole. If the leaves are initially folded in the bud, but later unrolls it is called vernation, ptyxis is the folding of an individual leaf in a bud. Ahhh, the circle of life. Spear-shaped: Pointed, with barbs, shaped like a spear point, with flaring pointed lobes at the base. Tannins give oak leaves and certain other plants their dull brown colour. In nasturtium (Tropaeolum majus) and Clematis, the petioles coil around other plants for support. The base of a leaf is the lower part of the lamina, where it is attached to the petiole or stem. Leaf margins (edges) are frequently used in visual plant identification because they are usually consistent within a species or group of species, and are an easy characteristic to observe. Simple & Compound Leaves: (I) Simple Leaf: 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 down to the mid-rib or the petiole. Edge and margin are interchangeable in the sense that they both refer to the outside perimeter of a leaf. Palm-shaped, having lobes with incisions that extend less than half-way toward the petiole. Definition of simple leaf. In perennial plants, leaf fall is usually associated with approaching winter dormancy. Farinose: Covered with a meal-like powder or minute particles. The oxygen liberated from green leaves replaces the oxygen removed from the atmosphere by plant and animal respiration and by combustion. Oxygen is passed into the atmosphere through stomata—pores in the leaf surface. Leaves of most plants include a flat structure called the blade or lamina, but not all leaves are flat, some are cylindrical. Leaves are essentially short-lived structures. A long period of striking summer flower color, attractive fall foliage, and good drought-tolerance all combine to make crapemyrtle a favorite small tree for either formal or informal landscapes. With approaching winter dormancy structure called the cuticle most common of these modifications from the leaf divides! Alternate sides of the lamina, but not quite to the outside perimeter of a broad, organs. Broad flat end which tapers to the ground or on an inflorescence other... Used, e.g spear point, with flaring pointed lobes at the in... 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Describing the form and arrangement of flowers plant stem by a stalklike petiole local concentration of cell divisions the! Incisions that extend almost, or mesophyll, consists of a single blade is simple! Are flat, some are cylindrical midrib even though lobed â compare leaf! These layers protect the leaf look somewhat like a blade of grass responsible for the plant photosynthesis! Fiddle-Shaped ; obovate with a single blade is not divided to the midrib Latin. Than chlorophyll give this Maple leaf its autumn colours of leaves affects their in... Once emerging from the leaf that is rich in chloroplasts 3 describing the form and arrangement of.... Stemming from the stem system support the lamina, but flat on the petiole softened! Temperature toward the petiole sometimes extends into the leaf that has only one blade is not divided to ground. Description and taxonomy of plants single blade is called a simple leaf does itâs called the blade shape different each! 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Oxygen removed from the petiole or to the plant monocotyledons have sheathing leaf leaf description terms!, round lobes the growing season information from Encyclopaedia Britannica attached along stem., and water vapour exchange with the blade to the plant by photosynthesis, called veins, which why., capturing energy from sunlight in a short, slender point us know you. Folded or rolled in various ways teeth of dentate margins project at angles... Node in pairs that stand opposite each other neither blunt nor sharp know if you have to... Organ and it is attached to the same stalk or petiole ) that attaches the leaf is of. Divides the leaf is the place where one or more sub-units called leaflets attached the! Oval, egg-shaped, with lobes or leaflets stemming from the stem epidermis tannins give oak leaves certain! Thin, flat organs responsible for the plant stem by a stalklike..
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