Anatomy of Flowering Plants PDF

# Anatomy of Flowering Plants ## Anatomy of Angiosperms * Study of internal structure. * Here we will study only about the Anatomy of Angiosperms, Dicots and Monocots. ## The Tissue A group of cells having common origin and function. ### Meristematic Tissue * Actively dividing cell. * Stored f...

# Anatomy of Flowering Plants ## Anatomy of Angiosperms * Study of internal structure. * Here we will study only about the Anatomy of Angiosperms, Dicots and Monocots. ## The Tissue A group of cells having common origin and function. ### Meristematic Tissue * Actively dividing cell. * Stored food - not present. * Thin walled. * Intercellular space - not present. * Continuously dividing (undifferentiated). * Immature cells. * Vacuoles - not present/Negligible/Small. * Nucleus - prominent. * Dense cytoplasm. ### Permanent Tissue Based on Capability of division * Cells do not divide further. * Cells undergo differentiation - physiological function. * To perform a specific function. * Stored food - present. * Thick wall. * Intercellular spaces - present/not present. * Mature cells. * Large vacuoles. ## Meristem Based on Location (Position) in Plant Body ### Apical Meristem * Present at the Apex (Tip). * Shoot tip * Root tip * Shoot Apical Meristem - Meristem present at shoot tip. * Root Apical Meristem - Meristem present at root tip. * Responsible for growth in length of root and shoot. * Primary Growth - Length of plant seen. While a length of meristem is small, the Apical meristem is left behind. * Also known as Primary Meristem, since birth. ### Intercalary Meristem * Occurs between mature tissues. * At node (Intercalary meristem present). * Between two internodes (mature). * It increases length. * Performs primary growth. * Can regenerate parts removed by grazing herbivores. * **Ex:-** Grasses, internode, Bamboo, Monocot stems, Sugarcane. ### Lateral Meristem * Present on the lateral side. * Increases thickness (or) girth (or) Diameter. * Also know as cylindrical meristem. * Performs secondary growth. * Known as secondary meristem. * Later on, it develops. ## On the Basis of Origin ### Primary Meristem * Present from beginning of plant. * Involved in primary growth. * **Ex:-** Apical Meristem (Shoot + Root), Intercalary meristem. * To perform primary growth. * Involved in primary growth. ### Secondary Meristem * Develop later on. * Involved in secondary growth (thickness). * **Ex:-** Lateral Meristem - * **Fasicular vascular cambium** * **Interfasicular cambium** * **Cork cambium** ## Promeristem (Embryonic Meristem) * **Divide** - Dividing cells * **No specific function** * **Differentiate** - Loss of division, gain of specialization. * **De-differentiation** - Loss of specialization, gain of division. * **Redifferentiation** - loss of specialization, gain of division. #### 1° Permanent Tissue * Formed by 1° meristem. * Gain of division. * Gain of specialization. * **Ex:-** 1°xylem, 1°phloem, medullary rays. #### 2° Permanent Tissue * Formed by 2° meristem. * Gain of specialization. * **Ex:-** 2°xylem, 2°phloem, medullary rays, cork cells. ## Permanent Tissues * The cells of permanent tissue do not divide further. * They gain specialization. ### Simple Permanent Tissues * **Structure, function similar.** * **They are made up of 2 or 1 type of cells - perform common function** * They are of 3 types: * **Parenchyma** * **Collenchyma** * **Sclerenchyma** #### Parenchyma * **Most active, first evolved, precursors** * It is a living tissue (Protoplasm present). * It forms bulk (major component). * Found in cortex, pericycle, mesophyll, pith. * **Cell wall (main)** - Made up of cellulose & pectocellulose. * **Intercellular space** - present/not present. * **Shape** - Generaly isodiametric (All cells are same in size). * **It can be round (spherical), oval, elongated, polygonal** * **Large central vacuole** - so nucleus will be periphery. * **Universal tissue** #### Functions * **Storage of food** - As they have large vacuoles. * **Help in secretion.** * **Perform photosynthesis, provide buoyancy.** #### Modifications * **Chlorenchyma** - parenchyma + chloroplast. * **Aerenchyma** - parenchyma + air cavity. * **Lying aquatic plants (help in floating)** #### Collenchyma * **It is a living tissue** * Elastic - Strength, support - mechanical. * **Deposition of pectin** (mainly), cellulose, hemicellulose - At corners. * **No intercellular spaces**. * **Shape** - More a less elongated. * **In transverse section** - oval/spherical/rounded/polygonal. * **Chloroplasts** - Found in collenchyma & assimilate food #### Occurrence * **Present below epidermis (stems of dicots).** * **Present in monocots.** * **Present in margins of leaf lamina & petiole of leaves.** * **Collenchyma gives mechanical support.** #### Functions * **mainly Photosynthetis** By parenchyma, but sometimes collenchyma too. * **Provide mechanical support to** - **Young stems, petiole of leaf.** * **Photosynthesis** #### Sclerenchyma * **Hard tissue**. * **Dead** (Protoplasm - not present). * **Mechanical tissue** * **Shape** - Long, narrow, thick walled, **Lignified**. * **Cell wall thickening** - Cellulose + hemicellulose + **Lignin**. * **Impenetrable to water.** * **Cells become strong and rigid. * **Lignified cell wall provides mechanical support.** #### Occurrence * **Found in hypodermis of monocot stem.** * **Isobilateral** (monocot leaf). * **Bundle sheath of monocot stem.** #### Types of sclerenchyma on basis of structure, origin, development, function. #### Sclereids * **Polygonal.** * **Pitted** - Reduced/small. * **Obliterated lumen** - Present in pulp of fruit (guava, pear, sapota), leaves of tea, fruitwall of nuts, seed coats of legumes. #### Sclerenchymatous Fibres * **Cylindrical (thick), elongated (tapering ends).** * **Point** (tapering ends). * **Pits present**. * **Provide mechanical strength**. * **Lumen obliterated (reduced/small).** * **Coconut fibres.** ### Complex Permanent Tissues * **Composed of >1 type of cells.** * **Xylem and phloem.** #### Features * **Conduction of water and minerals**. * **Mechanical support**. #### Xylem * **Dead conducting tissue** * **Support, provide mechanical support.** * **Lignin deposition** * **Tracheids:** * **Elongated (or) tube like dead cells** * **Thick and lignified cell wall.** * **Possess narrow lumen (one tube, one cell).** * **Tapering ends**. * **Gymnosperm tracheids are chiefly conducting tissue (95%)** * **Vessels (tracheal)** * **Cylindrical**. * **Perforated ends.** * **Made of many vessels - it looks like a single element.** * **Multicellular - as cell wall is not present.** * **Lignified cell wall - dead.** * **Lumen present - to conduct (10 min)** (one tube, many cells). * **Xylem fibers (wood fibers)** * **Obliterated central lumen.** * **Elongated, tapering ends.** * **Pitted, mechanical strength.** * **Thick, lignified walls.** * **Xylem parenchyma** * **Cells - living** * **Thin walled** * **Cellulosic** * **Storage** * **Help in radial conduction of water.** * **Medullary rays (present).** #### Phloem * **Conduction/translocation of food.** * **Living conducting tissue.** * **Sieve tube:** * **Living** * **Contain numerous pores.** * **In mature sieve tube - Nucleus - not present.** * **Functions are controlled by companion cells.** * **Sieve tube and companion cells are connected via pit fields - longitudinally.** * **Companion cells and sieve tube are ontogenetically related (same origin).} * **Companion cells:** * **Sister cells.** * **Nucleus present.** * **Living.** * **Specialized parenchyma cell.** * **Cellulosic cell wall.** * **Maintain pressure gradient.** * **Phloem parenchyma:** * **Only in dicots.** * **Living cell.** * **Thin wall.** * **Cellulosic cell wall.** * **Prominent nucleus.** * **Dense cytoplasm.** * **Phloem Fibers:** * **Only in 2° phloem.** * **Dead (slcerenchymatous) - not present in 1° phloem** * **Also known as bast fibers.** * **Elongated, tapering.** * **Commercially important - used as fibers.** * **Provide support, lignified.** * **Ex:-** Jute, flax, hemp. #### Types ##### Xylem * **Protoxylem:** * **First formed.** * **Small diameter** * **Size** * **Metaxylem:** * **Later formed.** * **Size** * **Fibers - not present.** * **In root and stem - protoxylem and metaxylem have a different arrangement.** * **Root** - **Exarch** - protoxylem towards outside * **Stem** - **Endarch** - protoxylem towards inside. * **Primary xylem is formed during primary growth.** * **Primary xylem is permanent tissue.** * **It is formed from promeristem.** * **Primary xylem differentiates into protoxylem, metaxylem.** * **Secondary xylem is formed during secondary growth.** * **Secondary xylem is permanent tissue.** * **It is formed from vascular cambium.** * **Secondary xylem differentiate into protoxylem and metaxylem.** ##### Phloem * **Protophloem:** * **First formed.** * **Metaphloem:** * **Later formed.** * **Primary phloem is formed during primary growth.** * **Primary phloem is permanent tissue.** * **It is formed from promeristem.** * **It differentiates into protoxylem and metaxylem.** * **Secondary phloem is formed during secondary growth.** * **Secondary phloem is permanent tissue.** * **It is formed from vascular cambium.** * **It is formed from meristematic tissue and differentiates into protoxylem and metaxylem.** * **No protophloem, metaphloem.** * **Primary phloem is formed during primary growth.** * **Primary phloem is permanent tissue.** * **It is formed from meristematic tissue and differentiates into protoxylem and metaxylem.** ## Tissue Systems Based on their structure, location. ### Epidermal Tissue System * **Dermal.** * **Outermost layer** * **Epidermis** * **Epidermal appendages** * **Root hairs.** * **Stem trichomes.** * **Epidermal structures** * **stomata (leaf)** #### a. Epidermis * **Outermost layer** * **Parenchymatous tissue with no intercellular spaces.** * **Usually single layered.** * **No chloroplast**, except in epidermis of leaf. * **Cuticle (waxy thick layer)** - it is present in epidermis to prevent loss of water. * **Cuticle** - **Not present in roots. ** * **Small cytoplasm and large vacuoles.** #### Epidermal Appendages * **Root hairs:** * **Epidermis of root.** * **Not present in submerged plants.** * **Absorption of water and nutrients.** * **Also known as epiblemma/rhizodermis/piliferous layer.** * **Outermost layer of plant root.** * **Elongation of epidermal cells.** * **Always unicellular.** * **Cuticle - Not present.** * **Trichomes (or) stem hairs:** * **Epidermis of stem.** * **Multicellular.** * **Branched or unbranched.** * **Can be** - Soft/stiff. * **Prevent secretion (function).** * **Maybe secretory in function.** * **Cuticle present - Made up of cutin.** * **Cuticle prevents excess transpiration** * **Stomata** * **Present on epidermis of leaves, lower, upper.** * **Adaxial epidermis** * **Upper epidermis** * **Dicot leaf - Thick cuticle, less no. of stomata - not present.** * **Monocot - Thick cuticle, less no. of stomata - not present.** * **Modified & form bulliform cells in dicots.** * **Curl inwards during stress conditions.** * **Abaxial epidermis.** * **Lower epidermis.** * **Thick cuticle.** * **More stomata.** * **Equal no. of stomata.** #### Stomata * **Minute structures (or) pores on epidermis of leaf.** * **Dicot stomata:** * **Epidermal cells.** * **Subsidiary cells (accessory cell).** * **Guard cells** * **Chloroplast.** * **Stomatal pore (stoma).** * **Modified epidermal cell for protection.** * **Kidney shaped guard cells.** * **Monocot stomata (Grasses):** * **Epidermal cells.** * **Guard cells.** * **Subsidiary cells** * **Dumbbell shaped guard cells.** #### Stomatal Apparatus * **Stomatal pore + guard cell + subsidiary cell.** #### Function * **Exchange of gasses.** * **Transpiration.** * **Guard cells regulate exchange of gasses by opening and closing of stomata.** * **Turgid - Open.** * **Flaccid - Close.** #### Functions of Epidermal Tissue System * **Protection:** - Outermost layer * **Secretion:** - Trichomes - Secretory parenchyma * **Gaseous Exchange:** - By stomata. * **Control of transpiration:** - Cuticle present in leaf and stem. * **Absorption of water and minerals:** - By root hairs. ### Ground Tissue System * **Largest tissue system.** * **All tissues except epidermis and vascular bundle.** * **GTS (Cortex) present below epidermis, protective (1-multilayered)** * **Hypodermis (just below epidermis) protective, 1-multilayered, store food + gasses exchange..** * **General cortex (parenchymatous) - transport nutrients, storage, mechanical support.** * **Endodermis - All tissues inner to endodermis (known as stele).** * **Regulate movement of water.** * **Pericycle - Mechanical support, storage.** * **Medullary rays - transport, storage, protection.** * **Pith (present) - Parenchymatous, stores food (starch) - delivers to leaves, roots, stem.** * **GTS - Made up of simple tissues - parenchyma, collenchyma, sclerenchyma.** * **GTS - Form main bulk of plant** ### Vascular Tissue System * **Vascular tissues consist of complex tissues - xylem, phloem.** * **Vascular bundles:** * **Xylem and phloem collectively known as vascular bundles.** * **On basis of location of xylem and phloem.** * **Root** - **Radial vascular bundle.** * **Stem** - **Conjoint vascular bundle.** * **Leaf** - **Conjoint vascular bundle.** * **If xylem and phloem present on same radii.** * **On basis of the presence of cambium:** * **Open** * **Fasicular cambium present.** * **Phloem on inner side of cambium.** * **Closed** * **No cambium.** * **Phloem on outer side of xylem.** * **Xylem and phloem arranged in different vascular radii.** * **Cambium** - not present. * **Ly meristematic layer.** * **Helps in secondary growth in dicots.** * **Develops later on in case of dicots. ** * **Promote growth.** #### Development of 1° Xylem * **Centrifugal:** Towards periphery, metaxylem. * **Centripetal:** Towards centre, protoxylem. #### Development of 2° Xylem * **Conjoint Collateral Open:** * **Cambium present.** * **Open for 2° growth.** * **Ex:-** Dicot stem, gymnosperms. * **Conjoint Collateral Closed:** * **Cambium not present** * **Closed for 2° growth.** * **Ex:-** Monocot stem, leaves of angiosperms. #### Development of Xylem in Roots * **Exarch -** protoxylem towards outside, metaxylem towards inside. * **Endarch -** protoxylem towards inside, metaxylem towards outside. #### Anatomical Features of Dicotyledonous Stem **A. Epidermis** * **It is outermost protective layer of stem.** * **Made up of elongately arranged cells.** * **Cells arranged compactly.** * **It is single layered.** * **It lacks chloroplast.** * **It is covered with a thin cuticle layer. ** * **It is absent.** * **Multicellular hairs (trichomes) are present.** * **Multicellular hairs help in preventing water loss.** * **Trichomes are present.** **B. Cortex** * **Epidermis and pericycle constitute 3 zones. ** * **In dicot stem, cortex is divided into 3 zones.** * **Hypodermis** * **General cortex** * **Endodermis** #### Hypodermis * **Composed of collenchyma. ** * **It is multilayered, thick** * **It is 2-3 layered thick** * **Stem is more elastic**. * **Stem is more rigid.** * **Often contains chloroplasts.** * **Provide mechanical support to plant.** #### General Cortex * **Composed of rounded, thin walled parenchyma with intercellular spaces.** * **Main function - storage of food.** * **It produces resin.** * **Resins protect stem from insects or mechanical damage.** #### Endodermis * **Single layered, thick walled parenchymatous cells** * **Endodermis is present between cortex and pericycle.** * **Intercellular spaces are absent.** * **It prevents leakage of water from stele.** * **It is absent.** #### Pericycle * **It is situated in front of vascular bundles.** * **A few layers of radially arranged parenchymatous cells between vascular bundles called pith (or) medullary rays.** * **It is made up of alternating bands of parenchyma and sclerenchyma.** * **It is not present.** #### Medullary rays * **Radial conduction of food and water.** #### Pith (or) Medullary rays * **A large number of rounded parenchyma cells with large intercellular spaces occupy central portion of stem.** #### Vascular bundles * **Wedge shaped vascular bundles.** * **Vascular bundles are arranged in a ring.** * **It is a characteristic feature of dicot stem.** * **Vascular bundle is conjoint, collateral, and open. Xylem is endarch.** * **Conjoint, collateral, and closed)** * **Xylem is endarch. ** * **Peripheral vascular bundles are smaller.** * **Peripheral vascular bundles are smaller than central vascular bundles but more in number.** * **Each vascular bundle is surrounded by sclerenchymatous bundle sheath.** #### Anatomical Features of Monocotyledonous Stem **A. Epidermis** * **It is outermost protective layer of stem** * **It is outermost thick, single layered. ** * **It is covered with thick cuticle layer.** * **It is absent.** * **Multicellular hairs are present.** * **Epidermis plays an important role in protection.** **B. Cortex** * **Epidermis and pericycle constitute 3 zones.** * **It is not present.** * **In the monocot stem, cortex is divided into 3 zones.** * **Hypodermis** * **General cortex** * **Endodermis** * **Hypodermis** * **Made up of schlerenchyma.** * **It is 2-3 layered, thick.** * **Stem is more rigid.** * **General cortex** * **Composed of rounded, thin walled parenchyma with intercellular spaces.** * **Main function - storage of food.** * **It produces resin (protects stem from insects or mechanical damage).** * **Endodermis** * **Single layered, thick walled parenchyma cells.** * **It is present between cortex and pericycle.** * **Intercellular spaces are absent.** * **It prevents leakage of water from stele.** * **It is absent.** **C. Vascular bundles** * **Vascular bundles are scattered in ground tissue.** * **It is conjoint, collateral, and open.** * **Xylem is endarch.** * **In Cucurbita, major part of water is in xylem.** * **Each vascular bundle is surrounded by a sclerenchymatous bundle sheath.** **D. Pith** * **It is large and well developed. ** **E. Vascular bundles** * **Protoxylem is first formed.** * **Protoxylem is one or two small vessels.** * **Metaxylem is later formed** * **Metaxylem is two large vessels.** * **There is a water cavity.** * **Water cavity occurs as a Schizolysigenous origin.** * **It is partially formed by separation of cells.** **F. Phloem** * **Phloem consists of living, thin walled companion cells.** * **Companion cells are associated with sieve tubes.** * **It helps in translocation of food material.** * **Phloem parenchyma is absent.** #### T.S of Cucurbita Stem * **It is uniseriate (single layered) outermost layer.** * **It is not present.** * **Cuticle and stomata are absent.** * **Many unicellular hairs are formed due to elongation of cells.** * **Elongation of cells is not seen generally.** * **Made up of thin walled parenchymatous cells with intercellular spaces.** * **Chloroplast is absent so they are non-photosynthetic.** * **Innermost layer of cortex.** * **Comprises of a single layer.** * **Without intercellular spaces.** * **It is situated between the pericycle & Cortex** * **Parenchyma beside the tangential walls of cells show suberin deposition.** * **Casparian strips are present.** * **Made up of cells which is made up of lignin and suberin (mainly).** * **Suberin is a waxy material. ** * **It is water impermeable.** * **Protoxylem is devoid of casparian strips (discovered by Caspari)** * **It is called the passage path cell.** * **It provides a path to absorb water from cortex to pericycle.** * **Intercellular spaces are absent between cells of endodermis. ** * **Endodermis acts as a dam to prevent leakage of water from stele.** * **It is single or a few layers of thick walled parenchymatous cells.** * **It is present.** * **Lateral roots occur from cells of pericycle.** * **Lateral roots are endogenous because they originate from stele.** * **It is present.** * **A few layers of radially arranged parenchymatous cells between vascular bundles called pith (or) medullary rays.** * **It is made up of alternating band of parenchyma and sclerenchyma.** * **It is not present. ** * **Radial conduction of food and water.** * **A large number of rounded parenchymatous tissues with large intercellular spaces occupy the central portion of the stem.** * **Wedge shaped vascular bundles are scattered in ground tissue.** * **It is a characteristic feature of dicot stem.** * **Vascular bundles are conjoint, collateral, and closed.** * **The peripheral vascular bundles are smaller than the central vascular bundles, but more in number.** * **Each vascular bundle is surrounded by a sclerenchymatous bundle sheath.** * **It is large and well-developed.** #### T.S. of Monocotyledonous Root * **Epiblema/Epidermis:** * **It is uniseriate (single layered) outermost layer.** * **It has cuticle and stomata are absent.** * **Many unicellular hairs are formed due to elongation of cells.** * **Elongation of cells is not seen generally.** * **It is the inner most layer of cortex ** * **Comprises of a single layer.** * **Without intercellular spaces.** * **It is situated between pericycle & Cortex.** * **Barrel shaped cells, parenchyma beside the tangential walls of cells show suberin deposition.** * **Casparian strips are present.** * **Made up of cells which is made up of lignin and suberin (mainly).** * **Suberin is a waxy material.** * **It is water impermeable.** * **Protoxylem is devoid of casparian strips (discovered by Caspari).** * **It is called the passage path cell.** * **It provides a path to absorb water from cortex to pericycle.** * **Endodermis acts as a dam to prevent leakage of water from steal** * **It is single or a few layers of thick walled parenchymatous cells.** * **It is present.** * **Lateral roots occur from cells of pericycle.** * **Lateral roots are endogenous because they originate from stele.** * **It is present.** * **A few layers of radially arranged parenchymatous cells between vascular bundles called pith (or) medullary rays.** * **It is made up of alternating band of parenchyma and sclerenchyma.** * **It is not present. ** * **Radial conduction of food and water.** * **A large number of rounded parenchymatous tissues with large intercellular spaces occupy the central portion of the stem.** * **Wedge shaped vascular bundles are scattered in ground tissue.** * **It is a characteristic feature of dicot stem.** * **Vascular bundles are conjoint, collateral, and open.** * **The peripheral vascular bundles are smaller than the central vascular bundles but more in number.** * **Each vascular bundle is surrounded by sclerenchymatous bundle sheath. ** * **It is large and well developed.** * **Monocotyledonous Root** * **Epiblema** ­­­­­­­­­­­­­ * **Cortex** * **Endodermis** * **Pericycle** * **Vascular bundles** * **Passage cells** * **Protoxylem** * **Metaxylem** * **Phloem** * **Pith** * **Dicotyledonous Root** * **Epiblema** * **Cortex** * **Endodermis** * **Pericycle** * **Vascular bundle** * **Protoxylem** * **Metaxylem** * **Phloem** * **Pith** * **T.S. of Monocotyledonous Root ** * **Epiblema** ­­­­­­­­­­­­­ * **Cortex** * **Endodermis** * **Pericyle** * **Vascular bundles** * **Protoxylem** * **Metaxylem** * **Phloem** * **Pith** * **T.S. of Dicotyledonous Root** * **Epiblema** * **Cortex** * **Endodermis** * **Pericyle ** * **Vascular bundle** * **Protoxylem** * **Metaxylem** * **Phloem** * **Pith** * **Dorsiventral (Dicotyledonous) Leaf** * **Features:** * **Collateral** * **Anatomical features:** * **Cuticle is present on both surfaces, but cuticle on upper surface is more thick.** * **Epidermal cells are without chloroplast.** * **The tissue between the upper and lower epidermis is differentiated into 2 mesophyll tissues.** * **Palisade parenchyma** * **Spongy parenchyma** * **Mesophyll cells have few intercellular spaces.** * **The palisade mesophyll tissue is made up of elongated cells, arranged vertically (or ventral) side, 2 or 3 layers below upper epidermis of the leaf.** * **Palisade tissue is towards adaxial or ventral side.** * **Palisade tissue is towards abaxial or ventral side.** * **Palisade tissue is made up of elongated cells, arranged vertically to each other, have more chloroplasts, thick cell wall, and do not allow gaseous exchange.** * **Photosynthetic cells form several layers around vascular bundles.** * **Lower epidermis has bigger thin walled cells with a large number of chloroplasts.** * **Bundle sheath made up of parenchyma.** * **Phloem is towards lower epidermis.** * **T.S. of Dorsiventral (Dicotyledonous) Leaf (Hypostomatic)** * **Isobilateral (Monocotyledonous) Leaf** * **Features:** * **Collateral** * **Anatomical features:** * **Cuticle is present on both surfaces, but cuticle on upper surface is more thick.** * **Epidermal cells are without chloroplast.** * **The tissue between the upper and lower epidermis is not differentiated into 2 mesophyll tissues.** * **Palisade parenchyma** * **Spongy parenchyma** * **Mesophyll cells have few intercellular spaces.** * **The palisade mesophyll tissue is made up of elongated cells, arranged vertically (or ventral) side, 2 or 3 layers below upper epidermis of the leaf.** * **Palisade tissue is towards adaxial or ventral side.** * **Palisade tissue is towards abaxial or ventral side.** * **Palisade tissue is made up of elongated cells, arranged vertically to each other, have more chloroplasts, thick cell wall, and do not allow gaseous exchange.** * **Photosynthetic cells form several layers around vascular bundles.** * **Lower epidermis has bigger thin walled cells with a large number of chloroplasts.** * **Bundle sheath made up of parenchyma. ** * **Phloem is towards lower epidermis.** * **T.S. of Isobilateral (Monocotyledonous) Leaf (Amphistomatic)**