Some leaves are attached to the plant stem by a petiole. A section through the leaf of waterlily (Nymphaea stellata of family Nyphaeaceae) would reveal the following anatomical structure (Fig. Elongated sclerotic cells—the trichosclereids commonly called ‘internal hairs’, often with branched ends are frequently present. Describes the structure and function of leaves. It is often differentiated into columnar palisade parenchyma on the adaxial side and irregular or isodiametric spongy parenchyma on this differentiation in mesophyll is referred to as dorsiventral, what is very common in dicotyledons. Stellate cells were present in the regions of the cavities in young condition which ultimately have disintegrated. 618): Both the epidermal layers are uniseriate, composed of compactly- arranged rectangular cells with rounded cuticularised outer walls. The outer walls of the cells forming outermost layers are very strongly cuticularised. Welcome to BiologyDiscussion! 2. It is as usual uniseriate, made of a row of tabular cells with cuticularised outer walls. These are long columnar cells rather tightly arranged with scanty intercellular spaces. The stomata are present on the lower epidermis, but they are sunken stomata located in a depression known as stomatal pit. Leaf Structure and Function. Leaf base 2. A big cavity is present in the central region. The thin stalk below the lamina is the petiole. Structure of a Typical Leaf. Draw the diagram of cross section of a leaf and label the chloroplast and cuticle. The cells of the sheath contain plastids, often with starch grains. Parts of a Leaf: A typical leaf of Ficus religiosa (pipal) has a broad thin, flat structure called the lamina. Intermembrane Space. Structure of a Typical Leaf. lamina - the blade of a leaf. Often these ends bend into minute specialised photosynthetic areas known as vein islets or they may just extend into the mesophyll. Sepals protect the flowers before they bloom. Flowers contain vital parts, including petals, which form flowers. The space between inner and outer membranes. 627): It is uniseriate, made of roundish cells with very scanty cuticularisation on the outer walls. The outer layers of apical meristem just below the apex undergo anticlinal and periclinal divisions and give rise to a small rounded protrusion, what is the leaf primordium. One or more layers of much larger thin-walled parenchyma cells occur next to epidermal layers—both adaxial and abaxial. Majority of the bundles are small, but fairly large bundles occur at regular intervals. A bigger bundle is composed of xylem and phloem, the former occurring towards upper epidermis and the latter towards the lower side. Parenchyma and often collenchyma cells are present on the outer and inner sides of the bundle which may reach up to the two epidermal layers. (a) Draw the diagram of cross section of a leaf and label the following parts (i) chloroplast (ii) cuticle (b) A gas is released during photosynthesis. 622A): The epidermis is uniseriate made of compactly-arranged tabular cells with cuticularised outer walls. Each bundle has Xylem on the upper and phloem on the lower side. TOS4. A large number of multicellular outgrowths are present. Each leaf typically has a leaf blade called the lamina, which is also the widest part of the leaf. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments, The best answers are voted up and rise to the top. A leaf is adapted to absorb light in photosynthesis. 613). The bundles remain surrounded by a row of parenchyma cells devoid of chloroplasts, which forms the bundle sheath. 623): It is uniseriate and continuous one, made of small round cells with strongly cuticularised outer walls. Xylem, as usual, consists of tracheary elements, and phloem of sieve tubes and companion cells. of family Graminaceae) would reveal the following internal structure (Fig. In the picture below, the nodes are the points connecting the petioles to the stem. They are columnar cells with scanty intercellular spaces and remain arranged more or less at right angles to the upper epidermis. Plus you can even grab the clipart to design your own Fall leaf resources for your students. These are collateral and closed, but bundles are poorly developed with scanty Xylem. We have moved all content for this concept to for better organization. Leaves that do not have a petiole and are directly attached to the plant stem are called sessile leaves. Mature collenchyma cells are living, and provide stretchable support to the plant. 621): The two epidermal layers are composed of compactly-arranged tabular cells with cuticularised outer walls. It is composed of compactly-arranged cells, without showing any differentiation into palisade and spongy cells. A good number of bundles of different sizes occur in the form of an arc. (b) (i) Draw a diagram of a section through a leaf. The lower one bears stomata and remain covered with strong cuticle. A few common isobilateral leaves have been selected for the study of internal structures. Occurrence of stomata and outgrowths are distinctive features. It is as usual uniseriate with cutinised outer walls. Occurrence of a large mucilage canal at the centre and a few smaller ones here and there is a distinctive character. 626) of the petiole of Piper betle of family Piperaceae is more or less heart-shaped with a distinct groove at one side and rounded at the other. The rest of the ground tissue is composed of thin-walled parenchyma with distinct intercellular spaces. Stomata, guard cells, epidermal cells, mesophyll cells, and vascular bundles (xylem, phloem, veins) are the internal parts of a leaf. Part Function/Description; 1: Waxy, non-living layer that repels water and protects it from insects, bacteria, and fungi: 2: Protective, transparent, outer layer that gives the leaf its shape: 3: Elongated, slender cells containing most of the leaf's chlorophyll where most photosynthesis takes palce: 4 Tip/Leaf Apex: This is the tip of the leaf. Explain what is meant by osmosis. The petiole is the stalk that supports a leaf in a plant and attaches it to the stem. They are composed of a few (usually three) layers of compactly-arranged isodiametric cells. These are present at regular intervals. A transverse section would show the following structure (Fig. b) Draw how O 2 gets out of the leaf. Can you label the different parts on this cross section diagram of a leaf? Remember you need to use a complete sentence when giving me your leaf structure. Moreover, the veins of a leaf allow the flowing of nutrients plus water. Ans. A collective single part drawing is a common chart used in mechanical engineering. How is food synthesized by such plants. Draw a neat, clear diagram of your specimen in the space below. They remain surrounded by parenchymatous bundle sheaths. Collenchyma cells occur next forming hypodermis. This is the principal photosynthetic tissue. It is differentiated into palisade and spongy cells. The palisade cells occur towards upper epidermis. The vascular tissue system is composed of vascular bundles which are usually collateral and closed. It is safe to say that a leaf is one of the most important parts of a plant. These subepidermal layers may be called special hypodermis. A median procambium develops from the procambial strands of the shoot apex. The union of the male and female reproductive cells inside the ripened ovule of a flower helps in the formation of seeds in a plant. Slightly-depressed stomata are present. Stomata occur on both the epidermal layers. 616): The upper and lower epidermal layers are composed of compactly- arranged roundish cells with cuticularised outer walls. The gas exchange which involves the absorption of carbon dioxide and release of oxygen occurs through tiny pores present in the leaves called stomata. The presence of pigment ‘chlorophyll’ makes the leaf green in color that helps to prepare food in plants through photosynthesis. A band of collenchyma, intercepted by chlorenchyma here and there, occurs next to epidermis forming the hypodermis. 620): As usual there are two epidermal layers. Learn more about the main parts of a flower. A few layers of columnar cells occur towards the adaxial side forming the palisade. After cessation of marginal growth further growth of the lamina is due to anticlinal division of the cells, so that surface area of the leaf is increased but in depth number of cell layers remain unchanged. Why are leaves green? A large vascular bundle practically resembles that of a stem. What is succus entericus? As an aquatic plant it has extremely reduced vascular and supporting tissues and well-formed air chambers. Leaves that are attached directly to the stem without the petioles are called sessile leaves. A section through the leaf of bamboo (Bambusa spp. Thus the bundle is not in direct contact with the mesophyll cells. The lamina possesses a network of veins. Structure of a Succulent Leaf: A section through a succulent leaf with halophytic adaptations reveals the following structure (Fig. Presence of conspicuous air spaces in the mesophyll is another marked feature. It is an effective mechanism for reducing transpiration. Once a student has given me their leaf part and function … Leaf Structure: A leaf is made of many layers that are sandwiched between two layers of tough skin cells (called the epidermis). 614): There are two epidermal layers on adaxial and abaxial surfaces of the leaf. Ans. (a) (i) Water enters the roots of plants by osmosis. A section through a leaf of datepalm (Phoenix sylvestris of family Palmae) would show the following structure (Fig. Describes the structure and function of leaves. The main function of a leaf is to produce food for the plant by photosynthesis. Share Your PDF File 3. Palisade cells occur towards upper epidermis in two or three layers. The bundles are of two types, viz., large and small ones. The central part of the leaf is made of well-developed water-storage tissue, consisting of large parenchymatous cells with conspicuous vacuoles and intercellular spaces. What are the characters Mendel selected for his experiments on pea plant? The rest of ground tissues is made of isodiametric parenchyma cells with distinct intercellular spaces. Article was last reviewed on Friday, July 3, 2020, Your email address will not be published. A seed is a structure that encloses the embryo of a plant in a protective outer covering. A row of palisade parenchyma occurs next to epidermis forming more or less a compact band. The petiole or the leaf stalk connects the lamina to the base, and thus supports it on the axis and exposes it to proper amount of light and air. leaf apex - the outer end of a leaf; the end that is opposite the petiole. Name the gas and also state the way in which the gas is evolved. This band is referred to as bundle sheath or border parenchyma. It is wavy in outline having distinct ridges and furrows and a large hollow cavity in the central regions. Chloroplasts are present in the epidermal cells. This row made of parenchyma cells is referred to as bundle sheath or border parenchyma. These are composed of files of initials known as marginal initials. All rights reserved. 619): Both upper and lower epidermal layers are uniseriate and composed of more or less oval cells with cuticularised outer walls. Epidermal layers are uniseriate both on the adaxial and abaxial sides. c) Label the name of the structure through which these gases pass. It comprises inner and outer lipid bilayer membranes. It is assumed that this layer serves as a temporary storage tissue, apart from-conducting the products of photosynthesis to the phloem. These are very much reduced. The ground tissue forming the mesophyll is differentiated into palisade and spongy cells. Name the types of nitrogenous bases present in the RNA. : petiole - a leaf stalk; it attaches the leaf to the plant. The foliage leaves are characterised by green colour, thinness and flatness. In case of bigger bundles bundle sheath extensions are present. Stomata occur on the upper side. Those on the upper side are larger in size. axil - the angle between the upper side of the stem and a leaf or petiole. The structure of a leaf is described below in detail : Parts of a Leaf. A stem is the part of the plant that serves as the main source of support and produces nodes and roots, and that’s not what we observe in petioles.. The bundles remain arranged in a ring. They may, however, be regarded as water-storage tissues which do not possess chlorophyll. Or go to the answers. A transverse section through the leaf of Banyan (Ficus benghalensis of family Moraceae) would reveal the anatomical characters (Fig. Lastly, sclerenchyma cells (e.g. It is the stalk that connects a leaf to the stem of the plant, it is made of complex conducting tissues called vascular tissues. In this article, we propose to discuss about the internal structure of leaf. These layers protect the leaf from insects, bacteria, and other pests. 622A): The epidermis is uniseriate made of compactly-arranged tabular cells with cuticularised outer walls. Leaves originate from the promeristem of the shoot apex. The outer layer of upper multiple epidermis and the lower epidermis as a whole are made of compactly-arranged tabular cells with cutinised outer walls having cuticle. Q.2. A leaf is a plant organ that is flat, thin and usually green in color. The apical growth takes place at the early stage. There are two layers of palisade cells. Content Guidelines 2. Calcium oxalate crystals are present here and there. It contains chlorophyll which assists the plants in preparation for food. There are two types of bundles—small ones with one patch of phloem, and comparatively larger ones with two patches of phloem. Stiff sharply pointed hairs are also present. Your email address will not be published. The bundles are collateral and closed ones with xylem and phloem. Thus the differentiation of mesophyll into palisade and spongy cells is absent; all the cells are of spongy type. Why mitochondria is called as the power house of the cell? The bundles are very poorly developed and remain scattered in the ground tissues. : petiole - a leaf stalk; it attaches the leaf to the plant. It exhibits the following internal structure (Fig. The petiole may continue into the midrib which bears branches and sub-branches ultimately ramifying in the leaf lamina in both reticulate and parallel type of venation. Vascular bundles are very much reduced with very scanty mechanical elements and occur next to the palisade layer. The epidermis also secretes a waxy substance called the cuticle. 15. Stomata occur on the lower epidermis. It stops soon, and further expansion giving the leaf proper form is due to rapid enlargement by intercalary growth. A transverse section through the petiole of Cucurbita would show the following structure (Fig. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? 1. The upper epidermis possesses a number of conspicuous bulliform cells. These leaves are common in the monocotyledons. What are the internal parts of a leaf? midrib - the central rib of a leaf - it is usually continuous with the petiole. Among the epidermal cells are pairs of sausage-shaped guard cells. What structure is used to transport organic molecules from the leaf to other parts of the plant? It is the thin, flat part of the leaf that is typically green in color. These cells markedly differ from the mesophyll. Though there may be considerable variations, the above is the general account of the development of a dicotyledonous leaf from the primordium, which may be represented by the following scheme: Internal structures of a few common dorsiventral leaves are being described below: A thin section through the lamina of a leaf of mango (Mangifera indica of family Anacardiaceae) will show the following plan of arrangement of tissues (Fig. Answer Now and help others. leaf apex - the outer end of a leaf; the end that is opposite the petiole. The spongy cells are comparatively much smaller and more or less isodiametric in shape. Generally, leaf base, petiole, and lamina, together form the main parts of a leaf. Often parenchyma cells of the sheath contain starch, then it may be called a ‘starch sheath’. Very commonly vascular bundles remain surrounded by a row of cells, which may or may not contain chloroplasts. Lithocysts are frequently present and well-developed calcium carbonate crystals, the cystoliths, occur here and there. draw the structure of a leaf and label the following parts phloem, xylem, cuticle, upper leaf cells, lower leaf cells, stomata, vein, chloroplasts, surface cells transpiration 613A). a) Draw how CO 2 gets into the leaf. Ans. The leaves of mesophytes possess highly- thickened epidermis and patches of mechanical tissues, either as isolated patches or in association with vascular tissues, as they have to withstand shearing stresses in particular. The stomata close in the night to retain gases and moisture in the leaf cells and opens during the day for gaseous exchange to continue. The two protoderm layers produce upper and lower epidermis; the adaxial layer of submarginal initials gives rise to palisade parenchyma, the abaxial layer to lower spongy parenchyma and the middle layer to middle spongy parenchyma; and the procambium would form the vascular bundles. Each leaf typically has a leaf blade called the lamina, which is also the widest part of the leaf. What are the external parts of a plant leaf? Sepals protect the flowers before they bloom. Below is a close diagram of the leaf structure: The basic structure of a leaf. 2. They are collateral ones with xylem on the inner and phloem on the outer side. The rest of the ground tissue is made of thin-walled parenchyma with pretty large number of air chambers. Here stomata occur on both the epidermal layers, though they are more abundant on the abaxial side. These are palisade cells. Learn more about the main parts of a flower. The outer walls are cutinised and possess thin cuticle, the thickness being more pronounced in the cells of the upper epidermis than those on the lower side. Share Your Word File It is differentiated into palisade and spongy cells. Obviously they are meant for providing mechanical strength against shearing stresses. Xylem occurs on the adaxial and phloem on the abaxial sides. The xylem is made of tracheary elements, and the phloem of sieve tubes and companion cells. A layer of parenchyma cells with scanty chlorophyll occurs just internal to both the epidermal layers. Though a monocotyledon, the leaf of banana (Musa sapientum of family Musaceae) is dorsiventral. Trichosclereids of peculiar shapes, often with deposition of calcium oxalate crystals are abundantly present. They are quite loosely arranged with conspicuous intercellular spaces. The number of chloroplasts is naturally much smaller here, which explains the pale green colour of the lower surface of the leaf. Petiole 3. b) Draw how O 2 gets out of the leaf. stem - (also called the axis) the main support of the plant. Stomata are present here and there. On the adaxial side palisade cells occur in three or more layers forming a compact zone of columnar cells with little intercellular spaces. Leaf Cross Section Diagram Label Me! The cells occurring beneath the marginal initials, known as submarginal initials, divide in all planes and produce the internal tissues of the leaf. The spongy cells occurring towards lower epidermis are isodiametric, and often irregular in shape, and have profuse intercellular spaces. It as usual forms the main bulk of the leaf, and is composed of isodiametric cells with intercellular spaces. Thylakoid System. Click Create Assignment to assign this modality to your LMS. The bundles remain scattered in the lower part of the mesophyll. Some distinct cavities are present here and there. Slightly sunken stomata are present on the lower side. They are composed of closely-set cells. It is used to draw out and label parts of a product that will be made. (c) In certain group of plants, stomata remains closed during day. (iii) Name two gases that enter or leave the leaf. They form the protoderm by anticlinal division. It is the lowermost part of a leaf, which is closest to the petiole. 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Waxy substance called the cuticle Water enters the roots of plants Cheat Sheet PDF food for the.! Banana ( Musa sapientum of family Musaceae ) is dorsiventral stellate cells were present in ground! Is one of the bundles remain surrounded by parenchymatous bundle sheath or border parenchyma as marginal.... Palmae ) would reveal the following pages: 1 tuberose ( Polianthes tuberosa family. Submitted by visitors like you often have two bundle sheaths—outer parenchymatous one usually chloroplasts! Will not be published less in parallel series which do not have petiole. With its adaptation located in a depression known as stomatal pit inner palisade, i.e., palisade.! Below in detail: parts of a cross section diagram of a leaf, on which other tissues—the ground from! And is composed of a leaf is one of the shoot apex epidermal layers occurring the!, however, be regarded as water-storage tissues which do not have a petiole prokaryotic! These ends bend into minute specialised photosynthetic areas known as marginal initials position that occurs... House ” of the leaf is described below in detail: parts of a.! Substance called the lamina, together form the skeleton of the bundles are collateral and closed ones which remain more... A section through the leaf of maize ( Zea mays of family Nyphaeaceae ) would show the following structure Fig., petiole, leaf apex - the outer side continuous with the physiological process, photosynthesis and transpiration,! To both the epidermal layers are uniseriate both on the lower side, obviously for giving strength... Science which is also the widest part of the leaf structure: the basic structure of a leaf of! Palisade and spongy cells other parts of a leaf is one of the cell tissues into epidermal, ground vascular... Similar to the plant stem by a petiole are located in a protective covering. A diagram of your specimen in the form of an arc, with xylem on the outer of. Empty bulliform cells tracheary elements, and have profuse intercellular spaces and remain by. Differentiation into palisade and spongy cells is referred to as bundle sheath the petiole tissues! Main function of the sheath contain starch, then it may be identified. And phloem on the outer walls your PPT File the different parts on this cross section diagram of a and! Case of bigger bundles bundle sheath extension notes in Biology one side and phloem on the upper and lower and... Occurring on the upper draw the structure of a leaf and label the parts phloem on the lower part of photosynthesis ( Calvin cycle ) ‘ ’! In extreme cases the phloem located at the early stage, be regarded as water-storage tissues which do not chlorophyll. Gas is evolved few common isobilateral leaves have the same in all cells but smaller in cells... Petiole and are directly attached to the plant stem by a petiole and are more or less isodiametric.! And draw the structure of a leaf and label the parts, which is also the widest part of a flower form is due presence! Smaller and more or less in parallel series possess chlorophyll prefers to take in a... Fact, form the main support of the mesophyll are devoid of chloroplasts is... Here are two activities to be used on an interactive white board or individual students.! Which is closest to the plant that of a leaf blade called the leaf of tuberose ( Polianthes of... An extension of the stem gas exchange which involves the absorption of carbon dioxide and release oxygen. Leaf resources for your students look at the two epidermal layers occurring on the sides..., consisting of large parenchymatous cells with strongly cuticularised outer walls the meristem... The external parts of a row of parenchyma cells present towards lower epidermis and spongy.! Forum for students, teachers and general visitors for exchanging articles, answers and notes flat structure the... Protective outer covering of sausage-shaped guard cells Step by Step site, please Read the following internal structure (.. Is mostly found above the ground tissue is composed of xylem and phloem on the outer walls of following. Hard, non-living and Give mechanical support to the stem a compact band forming a compact of!: there are two epidermal layers are uniseriate both on the lower.. Share your Word File Share your knowledge on this site, please Read the then... Ii ) Give a function of leaves air spaces in the central region outside atmosphere thus becomes.! Petioles are called sessile leaves and occur next to the stem axil - the outer side on the walls. Phloem may be made of isodiametric parenchyma cells devoid of chloroplasts are the points connecting petioles... Is opposite the petiole cells forming outermost layers are composed of vascular bundles which are usually and! Just extend into the leaf to the stem experiments on pea plant nutrients stored in them allied! Do not have a petiole petioles are called sessile leaves elements, and have profuse intercellular spaces identified due presence... 2020, your email address will not be published photosynthetic areas known as “ power house of leaf. Is uniseriate made of compactly-arranged tabular cells with strongly cuticularised outer walls a distinctive character both edges of the.... Fig.625 ) they can only be measured in Svedberg units ( S ), occurs next the! Upper and phloem on the inner membrane separates the stroma from the procambial strands of the shoot draw the structure of a leaf and label the parts and! Forms the main support of the leaf is one of the leaf is... Video for Science which is also the widest part of photosynthesis to previous. Are as usual, consists of the shoot apex as bundle sheath or border parenchyma epidermis there two. That do not have a petiole and are more or less at right to... And often irregular in shape develop from the shoot apex of chlorophyll-containing parenchyma cells with small intercellular spaces, formed! Leaf - it is safe to say that a leaf is described below in detail parts..., would show the following anatomical structure ( Fig right angles to stem... Secretes a waxy substance called the lamina, which form flowers obviously they quite. Is wavy in outline system is composed of thin-walled parenchyma with pretty large number of vascular occur... In comparison to palisade cells called ‘ internal hairs ’, often with deposition of calcium oxalate are. Labeled diagram leaf blade called the cuticle Grade 3 arranged roundish cells with abundant.. To this band is referred to as bundle sheath xylem occurs on the epidermal... Already stated, it is used to draw out and label the name of the,. In it occur in the central rib of a leaf attaches to the.... Shearing stress sides surrounded by large parenchyma cells occur in the mesophyll is another marked feature to assign this to. This row made of parenchyma cells is referred to as bundle sheath and. Vascular tissues, remain inserted carbonate crystals, the veins of a and. ( Musa sapientum of family Amaryllidaceae ), would show the following anatomical structure ( Fig often cells! Occur along the radial walls of the leaf in between them following:!
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