what is the common function of leaves?

The mesophyll cells enclose intercellular spaces which are, however, smaller than those of the typical spongy parenchyma. Leaves are collectively referred to as foliage, as in "autumn foliage". Multilayered epidermis is found in a few leaves like Ficus, Begonia and Nerium. Photosynthesis is the process when leaf cells containing chlorophyll take in carbon dioxide and water and using sunlight, make sugar and oxygen. Respiration is the process of obtaining oxygen and energy in the environment.. Leaves are an extension of the plant’s stem. Every life on the earth is directly or indirectly dependent on plants. The plant leaves are lateral outgrowth of the stem which develop from the meristematic tissues of buds. Kaner) or more than three (e.g., Alstonia) leaves develop from a single node. Unlike other epidermal cells, the guard cells possess a few chloroplasts. In Poinsettia (= Euphorbia pulcherrima, vern. However, it has a joint or constriction between the lamina and the petiole of the leaf. Bael), Butea (Dhak), Oxalis; (iv) Bifoliolate or binate (two leaflets, attached side by side at the tip of petiole, Fig. 5.59 A), e.g., Balanites, Hardwickia; (v) Unifoliolate (a single leaflet separated from the petiole by a constriction) e.g., Citrus (Fig. The latter is of two types— amplexicaul (enclosing stem completely as in Grasses, Wheat) and semiamplexicaul (enclosing the stem partially, e.g., Buttercup). The leaflets (pinnae or pinnules) differ from the whole leaves in the absence of axillary buds, basal stipules and origin in the same plane. The chlorenchyma of leaf is known as mesophyll. The leaves have chlorophyll for trapping sun energy. It consists of large isodiametric cells which appear oval or rounded in a transverse section. The leaves are commonly horizontal in orientation with distinct upper and lower surfaces. In other xerophytic plants, stomata occur individually and are sunken below the surface due to their being overtopped by accessory or subsidiary cells. Veins bear veinlet’s. 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. Functions 7. The cereals with a single bundle sheath are called panicoid grasses. Carnivorous plants use adapted leaves to capture their … (vii) The leaf base may possess two lateral outgrowths called stipules. ks1w4 : identifying and classifying 1a2 : Identify and describe the basic structure of a variety of common flowering plants, including trees A leaf having a single or undivided lamina is called simple leaf. Plant Parts While most students recognize the stem, leaves, and flowers of plants, fewer identify roots as a common structure. Palisade parenchyma may occur on both upper and lower sides with spongy parenchyma sand witched between the two, e.g., Nerium. Water absorbed by the root hairs of the plant is evaporated from the leaf surface during the day time. The cuticle is, however, less developed than at the adaxial epidermis. In some plants, it takes up the responsibility of reproduction also. This pattern is made up of much larger, primary veins that connect to the leaf stem as well as smaller, secondary veins. 4. Here the leaflets are borne laterally on an elongated axis. iso— equal, bi— two, lateris— side). Privacy Policy 3. The leaves are covered by mucilage. Call it what you like, the employee life cycle is a common buzz phrase in human resources. It has a photosynthetic pigment chlorophyll which converts solar energy into chemical energy. 58 E), e g Fennel Coriander (vern. Functions of Leaves: i. Explain its significance. The lamina is modified into pitcher. 5.57). Stipules fused with petiole, e.g., Rose, Groundnut. 13. Some plants show developmental heterophylly. Vascular strands represented by veins conduct water and minerals from stem to leaves in their xylem and transport organic materials from leaf blade to stem in their phloem. (ii) Palmate or Multicostate Reticulate Vena­tion: A number of prominent or principal veins arise from the tip of the petiole and reach either the apex or margins of the lamina. They contain chlorophyll that helps the plants to prepare their food using sunlight, carbon dioxide and water. It lies in between the two layers of epidermis. 5.61 G). They develop as lateral outgrowth from shoot apical meristem. They lead internally into sub-stomatal cavities or chambers. Lamina (= epipodium) or leaf blade is the terminal thin, expanded, green and conspicuous part of the leaf which is specialized to perform photosynthesis. Mesophyll is usually indistinguishable (or palisade tissue is present in equal amount on both the sides). Privacy Policy3. Internally, they have thin undifferentiated mesophyll. 2. (xi) Leaf bears abundant stomata for exchange of gases. The guard cells are further associated with a pair of specialized epidermal cells called subsidiary cells or accessory cells. 3. It is called sheathing leaf base. The bundle sheath of the larger veins show parenchymatous extensions towards both the upper and lower sides. Parallel venation is characteristic of monocots with the exception of a few (e.g., Smilax, Colocasia, Alocasia, Dioscorea). (i) Pinnate or Unicostate Parallel Venation: There is single principal vein or midrib that runs from base to the apex of the lamina. Hair may occur here and there. The vascular bundles are almost rounded. The Leaf. Fleshy leaves of Indian aloe, Portulaca and fleshy scale leaves of onion store food materials and water for the future of the plants. They are conjoint and collateral, i.e., they possess both phloem and xylem which lie on the same radius. The opposite leaves of the adjacent nodes lie at right angles so that four rows of leaves are formed on the stem, e.g., Calotropis (vern Ak), Sacred Basil (vern. In many legumes it is swollen. Some of the leaf segments are modified to form small bladders (1-3 mm in diameter). Cyclic phyllotaxy includes both opposite and whorled types of phyllotaxy. They are important vegetative organs which are specialised for photosynthesis. 5.61): In Wild Pea (Lathyrus aphaca, Fig. Not all plants have the same structures (stems, leaves, flowers, roots). The internal structure also does not show much differentiation of upper and lower sides. The leaflets resemble leaf in having base, stalk and blade. Fleshy and suc­culent leaves of xerophytic plants grow­ing in desert area always store a huge quantity of water, mucilage and food materials. The vascular bundles are conjoint, collateral and closed. Among the different parts of a plant, the leaf is the most essential. Stipules are fused from their outer margins to become opposite the leaf, e.g., Castor. Therefore, the two surfaces are equally green (Gk. As a result the leaf gets rolled up to reduce the exposed surface. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? A few upper leaflets of the pinnate compound leaves of Pea (Pisum sativum, Fig. In Begonia, adventitious buds develop in the region of injury. C. Evaporation of water. Gaajar). 5.59 E), although in reality its leaves are pinnately divided; (iii) Trifoliolate or ternate (three leaflets, Fig 5 59 В, C), e.g., Aegle marmelos (Wood Apple, vern. Mesophyll is absent in the region of midrib and other larger veins. Dharek, Drek). These phyllotaxic series are also called Schimper-Brown series in which each member of the series is the sum total of numerators and denominators of the two previous ones. All the green leaves of a plant are collectively called foliage. PreserveArticles.com is a free service that lets you to preserve your original articles for eternity. The lower surface is correspondingly called outer, abaxial or dorsal surface. In later chapters we will look at the various organs found in animals. Each stomate or stoma leads internally into an air space called sub-stomatal cavity or chamber. The stipules become foliaceous to perform e function of photosynthesis. A cuticlecan also sometimes be present on the outside of the epidermis. Phloem lies towards the lower side while xylem is found towards the upper side. 4. 5. Such an arrangement is called Kranz anatomy. The leaves perform three main functions such as manufacture of food, inter­change of gases between the atmosphere and the plant body and evaporation of water. 5.59 D), e.g., Paris quadrifolia; Marsilea also seems to have quadrifoliolate leaves (Fig. The petioles of Garden Nasturtium (Tropaeolum majus, Fig. The simple leaf is unicostate, that is, it has a single principal vein or midrib. Answer: The main function of leaf is photosynthesis. Stipules are foliaceous in Lathyrus aphaca to take part in photosynthesis. Leaf is a green, dissimilar exogenous lateral flattened outgrowth which is borne on the node of a stem or its branch and is specialised to perform photosynthesis. In Barberry, the leaves of the main stem are modified into branched 3-5 rayed spines. A distinct layer of cuticle occurs on the outside. It is also the part of the plant where respiration takes place. Instead, the undifferentiated mesophyll is similar to spongy tissue. The lamina can have various types of incions, which may reach upto half (-fid), more than half (-partite) or near the base of midrib (-sect). This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Characteristics of Leaf 3. It is called rachis. 5.61 D) are elongated, sensitive and capable of coiling around the support like the tendrils. Tulsi), Zinnia, Guava. 5.61 C) and Nepenthes (Fig. What are the general characters of bryophytes? The most important single function of the leaves is synthesis of organic food in the process of photosynthesis. Thornshelp protect the plant from being eaten. Structures within a leaf convert the energy in sunlight into chemical energy that the plant can use as food. A leaf with stipules is called stipulate while the one without stipules is termed as exstipulate. In larger vascular bundles xylem is similar to that of stem with two large, pitted, oval and lateral meta-xylem vessels connected by tracheids and smaller spiral or annular oval protoxylem vessels towards the upper side where a protoxylem lacuna or cavity is also present. Botanists call the upper side the adaxial surface (or adaxis) and the lower side the abaxial surface (or abaxis). 6. 5.61 F) are greatly elongated to function like the tendrils. The purpose or function of phyllotaxy is to arrange leaves in such a way that all of them get proper exposure to sunlight. Me­chanical tissue is absent. Amaltas), sesbania, Tamarind (vern.Imli). The finer branches do not form a reticulum. The palisade mesophyll cells enclose a number of narrow intercellular spaces for exchange of gases. Aerenchyma is present. Leaf base is often indistinguishable from the petiole. Mesophytic leaves may have stomata in the upper epidermis. They are modified into sepals, petals, stamens and carpels to take part in sexual reproduction. 1. (ix) The lamina possesses prominent vascular strands called veins. Double bundle sheath occurs in Triticum (Wheat) and some other cereals. Answer Now and help others. ), hooks (e.g., leaflet hooks of Doxantha unguiscati) and spines (e.g., Asparagus). One of the main functions of a stem is to pass water and dissolved minerals from the roots to the leaves. In these cases when leaf lamina touches the ground, the leaf margin at point produces roots and form a bud that grows into a new plant. 1. Xylem is formed of vessels, tracheids and xylem parenchyma. Their capture rainwater. 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. Angle between two successive leaves or angular divergence is calculated by multiplying the phyllotaxy with 360, e.g., 1/3 x 360 = 120. It may be replaced by a cavity. When simple, leaf is multicoatate, that is, it has a number of principal veins, In compound leaf, leaflets are borne jointly on the tip of the petiole. The main function of a leaf is to carry out photosynthesis, which provides the plant with the food it needs to survive. Even in Citrus many abnormal leaves bear two small leaflets just on the sides of the normal blade (Fig. They occur in the aquatic carnivorous plants of Utricularia (Bladderwort). Welcome to BiologyDiscussion! A leaf consists of three main parts- petiole, leaf base and lamina. 5.64). It is called ligule. Phloem fibres are rarely present. The leaves without stipules are called exstipulate. 5.61 B) and Sweet Pea (Lathyrus odoratus) are transformed into tendrils while the rest are normal. In this section, we will discuss how a plant leaf is an example of an organ. The leaf base is commonly sheathing, that is, covering the stem partially or completely. Biology, Leaf, Plants, Structural Organisation. 5.58 C). The preparation of food mate­rial takes place out of water and car­bon dioxide obtained from the soil and the air respectively. An organ is a collection of tissues joined together as a structural unit in order to perform a common function. Some leaves are used to store energy in bulbs. What are antibiotics? In Lentil (Lens culinaris, vern. A number of parallel running vascular bundles are embedded partially in the sclerenchyma found towards the lower side. Here the pinnate leaf is divided twice pinnately (Fig. Plants are made up of organs, including roots, leaves, the stem and reproductive organs.. Each organ has its own functions. Two Functions of the Leaf. Leaf: Characteristics, Types, Duration and Insertion, Dorsiventral Leaf, Isobilateral and Centric Leaf | Plants, Main Parts of a Typical Root (With Diagram) | Plants. The leaflets called pinnules, are borne on the secondary axes known as rachillae or rachules. Stipules of young leaves connate to protect bud, e.g., Ficus, Stipules are transformed into spines, e.g., Acacia, Zizyphus. Adjacent stipules of opposite leaves are fused to appear in between the petioles, e.g., Anthocephalus (Kadam), Ixora. The flattened lamina or leaf blade is supported by veins and veinlet’s which contain vascular tissues for con­duction of water, mineral salts and prepared food. The cells are thickened on the free side where silica and cutin are deposited. 15. Stipules are fused from their inner margins to become axillary, e.g., Gardenia. The palisade parenchyma or palisade mesophyll cells are rich in discoid chloroplasts. In xerophytic leaves, spongy parenchyma is reduced. 7. Phyllotaxy is written by taking the number of circles as numerator and the number of leaves as denominator, e.g., 1/3, 2/5, 3/8, 5/13, 8/21. 2. The leaves are generally cylindrical, e.g., Onion. 3. In epiphytic Dischidia the whole leaf is changed into an open pitcher for storing rain water. The foliage of some plants is economically important, e.g., Tea. The spines present on the areoles of Opuntia also represent the leaves. The arrangement of veins and veinlet’s on the lamina of a leaf is called venation. (ii) Providing channels for translocation of organic nutrients. PreserveArticles.com is an online article publishing site that helps you to submit your knowledge so that it may be preserved for eternity. 5.60 B). 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. They do not have roots in the ground. Leaves are the main seat of loss of water called transpiration. Their stomatal walls are thicker than the rest. 5.60). It gener­ally takes place through the stomatal openings. It protects the young axillary bud. The simplest type of such a phyllotaxy is alternate or spiral distichous in which the leaves of a branch form two alternate rows (e.g., Grass). 5.62 A). (i) Pinnate or Unicostate Reticulate Venation: The lamina has a single principal vein or midrib which extends from its base to apex. Leaves of the successive nodes lie in the same plane so that only two rows are formed on the stem, e.g., Quisqualis (Rangoon Creeper), Syzygium (=Eugenia, lambolana, vem, jamun). 5.53): Only one leaf is borne on a node and the leaves of the adjacent nodes roughly lie towards the opposite sides (e.g., Shoe Flower). PreserveArticles.com: Preserving Your Articles for Eternity, Here is your free sample essay on the leaf, Here is your summary on plant root and shoot system, Essay on the Conditions Necessary for Photosynthesis, Experiment to Show that Sunlight is Necessary for Photosynthesis. Our mission is to provide an online platform to help students to share notes in Biology. The spongy cells are very loosely arranged except around the vascular bundles. (x) It is green and specialised to perform photosynthesis. Veinlet’s are inconspicuous. The leaflets are commonly borne in opposite or sub-opposite (e.g., Murraya) pairs. The principal veins proceed towards the margins, e.g., Fan Palm (Livistonia). A distinction into upper and lower surfaces is absent. 3. The veins run parallel to one another. Our mission is to liberate knowledge. 5.58 B), e.g., Rose, Murraya, Neem (Azadirachta indica). The leaf is also involved in the transpiration process. The cuticle prevents excessive transpiration, helps bind epidermal cells and protects them from mechanical injury. The various parts of a typical isobilateral leaf (e.g., Maize) are as follows: A uniseriate or single-layered epidermis occurs on the two sides of the leaf. Xylem lies towards the upper side of the leaf while phloem is found towards the lower surface. The wide midrib does not contain any mesophyll. Water absorbed by the root hairs of the plant is evaporated from the leaf … It is chlorenchymatous. (ii) Scaly Very small dry membranous stipules, e.g., Cassia fistula. Leaves plays a vital function in plant processes like transpiration and guttation which is the process of removing excess water through the help of sunlight. We have moved all content for this concept to for better organization. At places the upper or adaxial epidermis contains groups of larger thin-walled protruding and turgid cells over the region of veins. Protection against transpiration by changing into phyllodes (expanded petioles) and forming spines. 2. The epidermis helps in the regulation of gas exchange. (iv) An axillary bud is often present in the axil of the leaf. 9. In Salvinia one leaf of each node is changed into roots that act as balancers for floating. What are the three important components of biodiversity? 12. 2. Prickles occur at various positions (mar­gins, apex, surface) on the leaves for the same purpose, e.g., Aloe, Solanum surattense (= S. xanthocarpum), Carthamus oxycantha. Each vascular bundle is surrounded by a single sheath of compactly arranged parenchyma cells called border parenchyma or bundle sheath. Incidentally this also causes transpiration. In the course of evolution, many species have leaves which are adaptedto other functions. 4. For this a large sub-stomatal cavity lies below each stoma. Share Your Word File Plants provide food for all life on the planet. Stipules fuse to form a sheath or ochrea around the stem, e.g., Rumex, Polygonum. Leaves protect the axillary and terminal buds from mechanical injury and desiccation. 2. They resemble the nails of a cat and hence the names of the plant, the hooks cling to the bark of the supporting tree very firmly and allow the plant to climb up. The inner and the radial walls of the epidermal cells are thin. 2. Hair may occur here and there. The lateral veins run parallel to one another without forming anastomoses, e.g., Banana (Musa paradisiaca), Canna. The plan of venation is similar to a hand. In a great number of plants, only one leaf grows from each node in an alternate pattern up the branch, such an arrangement is referred to as alternate. Give an example. There­fore, mesophyll constitutes the photosynthetic tissue of the leaf. Sepals are protective and green, petals are coloured and attractive, stamens are pollen bearing structures or microsporophylls while carpels are ovule-bearing megasporophylls. It is termed sessile if the petiole is absent. Parts 4. (vii) unfolding of the young leaves by means of motor or bulliform cells. They enclose large cavities or intercellular spaces which are connected with the atmosphere through the stomata. The veins also have a secondary purpose, which is to help provide support for the rest of the leaf. Each stoma or stomate is lined by a pair of dumb bell-shaped guard cells. Importance. Leaves are the most important part of a plant. Petiole : Petiole connects the lamina with the stem or the branch. They provide rigidity and mechanical strength to the leaf. 5.65). Mesophyll is not differ­entiated into palisade and spongy tissues. Sieve tubes conduct organic food. Leaf base (= hypo podium) is the lowermost part of the leaf by which the leaf is joined to the node of the stem. The leaves of one whorl generally alternate with those of the adjacent whorls in order to provide for maximum exposure. 6. It is safe to say that a leaf is one of the most important parts of a plant. Protection from browsing animals by producing spines, e.g., Barberry, Opuntia, Argemone mexicana, etc.