Class Science English · Part

AND PLANT PHYSIOLOGY Cuticle is present on the outer wall of epidermis to check evaporation of water. Trichomes and root hairs are the epidermal outgrowths. Functions: i) Epidermis protects the inner tissues. ii) Stomata helps in transpiration.

iii) Root hairs help in absorption of water and minerals. . . Ground Tissue System It includes all the tissues of the plant body except epidermal and vascular tissues like (i) Cortex (ii) Endodermis (iii) Pericycle (iv) Pith .

. Vascular Tissue System It consists of xylem and phloem tissues. They are present in the form of bundles called vascular bundles. Xylem conducts water and minerals to different parts of the plant.

Phloem conducts food materials to different parts of the plant. There are three different types of vascular bundles namely (i) Radial (ii) Conjoint (iii) Concentric (i) Radial Bundles Xylem and phloem are present in different radii alternating with each other. e.g. roots (ii) Conjoint bundles Xylem and phloem lie on the same radius.

There are two types of conjoint bundles. a) Collateral Xylem lies towards the centre and phloem lies towards the periphery. When cambium is present in collateral bundles, it is called open. e.g.

dicot stem and collateral bundle without cambium is called closed. e.g. monocot stem. b) Bicollateral In this type of bundle, the phloem is present on both outer and inner side of xylem.

e.g. Cucurbita (iii) Concentric Bundles Vascular bundle in which xylem completely surrounds the phloem or viceversa is called concentric vascular bundle. It is of two types: . Amphivasal: Xylem surrounds phloem.

e.g. Dracaena . Amphicribral: Phloem surrounds xylem. e.g.

Ferns Endarch: Protoxylem lies towards the centre and metaxylem lies towards the periphery. e.g. stem. Exarch : Protoxylem lies towards the periphery and metaxylem lies towards the centre.

e.g. roots. Table . Tissue system and its functions Tissue System Components Functions Dermal Tissue System Epidermis and Periderm (in older stems and roots) • Protection • Prevention of water loss Ground Tissue System Parenchyma tissue Chlorenchyma Collenchyma tissue Sclerenchyma tissue • Food storage • Photosynthesis • Support, protection • Support, rigidity Vascular Tissue System Vascular tissues - Xylem tissue - Phloem tissue • Transport of water and minerals • Transport of food Plant Anatomy and Plant Physiology .

Internal Structure of Dicot Root (Bean) A thin transverse section of dicot root shows the following structures. (i) Epiblema: It is the outermost layer. Cuticle and stomata are absent. Unicellular root hairs are present.

It is also known as Rhizodermis or Piliferous layer . (ii) Cortex: It is a multilayered large zone made of thin-walled parenchymatous cells with intercellular spaces. It stores food and water. (iii) Endodermis: It is the innermost layer of cortex.

The cells are barrel - shaped, closely packed, and show band like thickenings on their radial and inner tangential walls called casparian strips . But these casparian strips are absent in the endodermis cells which are located opposite the protoxylem these thin walled cells without casparian strips are called passage cell. It helps in the movement of water and dissolved salts from cortex into xylem. (iv) Stele: All tissues inner to endodermis constitute stele.

It includes pericycle and vascular bundle. (a) Pericycle: Inner to endodermis lies a single layer of pericycle. It is the site of origin of lateral roots. (b) Vascular bundle: It is radial.

Xylem is exarch and tetrach . The tissue present between xylem and phloem is called conjunctive tissue. In dicot root, it is made up of parenchyma. (c) Pith: Young root contains pith whereas in old root pith is absent.

. Internal Structure of Monocot Root (Maize) A thin transverse section of monocot root, shows the following characteristic features. i. Epiblema or Rhizodermis: It is the outermost layer of the root, and is made up of single layer of thin walled, parenchymatous cell.

Stomata and cuticle are absent. The root hair helps in absorption of water and minerals from the soil. This layer also protects the inner tissues. Figure .

Types of vascular bundle Xylem Xylem Xylem Xylem Phloem Phloem Phloem Cambium Outer Phloem Outer Cambium Inner Cambium Inner Phloem Radial Conjoint, collateral and open Conjoint, collateral and closed Conjoint, Bicollateral Concentric and Amphicribral Concentric and Amphivasal ii. Cortex: It is multilayered large zone, composed of parenchymatous cells with intercellular spaces. It stores water and food material. iii.

Endodermis: It is the innermost layer of cortex with characteristic casparian strips and passage cells. Casparian strips are band like thickening made of suberin . iv. Stele: All the tissues inner to endodermis constitute stele.

It includes pericycle, vascular tissues and pith. a) Pericycle: It is a single layer of thin walled cells. The lateral roots originate from this layer. b) Vascular tissues: It consists of many patches of xylem and phloem arranged radially.

The xylem is exarch and polyarch. The conjunctive tissue is made up of sclerenchyma. c) Pith: It is present at the center. It is made up of parenchyma cells with intercellular spaces.

It contains abundant amount of starch grains. It stores food. . Internal Structure of Dicot Stem (Sunflower) The transverse section of a dicot stem reveals the following structures.

. Epidermis: It is the outermost layer. It is made up of single layer of parenchyma cells, its outer wall is covered with cuticle. It is protective in function.

. Cortex: - It is divided into three regions: (i) Hypodermis: It consists of - layers of collenchyma cells. It gives mechanical support. Figure .

Transverse section of Dicot root A sector enlarged Ground plan Root hair Xylem Phloem Cortex Piliferous layer Pericycle Casparian strip Conjunctive tissue Phloem Endodermis Passage cell Root hair Piliferous layer Cortex Xylem Figure . Transverse section of Monocot root A sector enlarged Ground plan Root hair Piliferous layer Cortex Endodermis Pith Root hair Piliferous layer Casparian strip Endodermis Pericycle Phloem Xylem Pith Cortex Plant Anatomy and Plant Physiology (ii) Middle cortex: It is made up of few layers of chlorenchyma cells. It is involed in photosynthesis due to the presence of chloroplast. (iii) Inner cortex: It is made up of few layers of parenchyma cells.

It helps in gaseous exchange and stores food materials. Endodermis is the inner most layer of cortex it consists of a single layer of barrel shaped cells, these cells contain starch grains. So it is also called starch sheath . .

Stele: The central part of the stem inner to endodermis is known as stele. It consists of pericycle, vascular bundle and pith. (i) Pericycle: It occurs between vascular bundle and endodermis. It is multilayered, parenchymatous with alternating patches of sclerenchyma.

(ii) Bundle Cap: There is a patch of hard sclerenchyma tissue outside to the phloem of vascular bundle is calld Bundle Cap. (iii) Vascular bundle: Vascular bundles are conjoint, collateral, endarch and open. They are arranged in the form of a ring around the pith. (iv) Pith: The large central parenchymatous zone with intercellular spaces is called pith.

It helps in the storage of food materials. . Internal Structure of Monocot Stem (Maize) A transverse section of monocot stem reveals the following structures. .

Epidermis: It is the outermost layer. It is made up of single layer of parenchyma cells. It is covered with thick cuticle. Multicellular hairs are absent and stomata are also less in number.

. Hypodermis: It is made up of few layers of sclerenchyma cells interrupted by chlorenchyma. Sclerenchyma provides mechanical support to plant. .

Ground tissue: The entire mass of parenchyma cells next to hypodermis Table . Differences between Dicot and Monocot root S. No. Tissues Dicot Root Monocot Root Number of Xylem Tetrarch Polyarch Cambium Present (During secondary growth only) Absent Secondary Growth Present Absent Pith Absent Present Conjunctive Tissue Ex.

Parenchyma Bean Sclerenchyma Maize Epidermal hair Pith Xylem Cambium Phloem Bundle Cap Endodermis Parenchyma Chlorenchyma Collenchyma Epidermis Cuticle Epidermal hair Epidermis Hypodermis Cortex Endodermis Vascular bundle Pith Ground plan A sector enlarged Figure . Transverse section of Dicot stem and extending to the centre is called ground tissue . It is not differentiated into endodermis, cortex, pericycle and pith. .

Vascular Bundle: Vascular bundles are skull shaped and scattered in the ground tissue. Vascular bundles are conjoint, collateral, endarch and closed. Each vascular bundle is surrounded by few layer of sclerenchyma cells called bundle sheath . (a) Xylem: It consists of metaxylem and protoxylem.

Xylem vessels are arranged in V or Y shape. In mature vascular bundle, the lower most protoxylem disintegrates and form a cavity. This is called protoxylem lacuna. (b) Phloem: It consists of sieve tube elements and companion cells.

Phloem parenchyma, and phloem fibers are absent. . Pith: Pith is not differentiated in monocot stems. Table .

Differences between Dicot Stem Ex.Sunflower and Monocot Stem Ex.Maize S. No. Tissues Dicot Stem Monocot Stem Hypodermis Collenchymatous Sclerenchymatous Ground tissue Differentiated into cortex, endodermis, pericycle and pith Undifferentiated Vascular bundles (i) Less in number (ii) Uniform in size (iii) Arranged in a ring (iv) Open (Cambium present) (v) Bundle sheath absent (i) Numerous (ii) Smaller near periphery, bigger in the centre (iii) Scattered (iv) Closed (Cambium absent) (v) Bundle sheath present Secondary growth Present Mostly absent Pith Present Absent Medullary rays Present Absent . Internal Structure of Dicot Leaf (Dorsiventral Leaf) Ex.

Mango Leaf The transverse section of leaf shows the following structures. A sector enlarged Ground plan Vascular bundles Vascular bundles Bundle sheath Protoxylem Metaxylem Phloem Chlorenchyma Hypodermis Epidermis Cuticle Ground tissue Ground tissue Epidermis Figure . Transverse section of Monocot stem (i) Upper epidermis: This is the outermost layer made of single layered parenchymatous cells without intercellular spaces. The outer wall of the cells are cuticularized.

Stomata are less in number. Plant Anatomy and Plant Physiology (ii) Lower epidermis: It is a single layer of parenchymatous cells with a thin cuticle. It contains numerous stomata. Chloroplasts are present only in guard cells.

The lower epidermis helps in the exchange of gases. The loss of water vapour is facilitated through this chamber. (iii) Mesophyll: The tissue present between the upper and lower epidermis is called mesophyll. It is differentiated into Palisade parenchyma and Spongy parenchyma.

a) Palisade parenchyma: It is found just below the upper epidermis. The cells are elongated. These cells have more number of chloroplasts. The cells do not have intercellular spaces and they take part in photosynthesis.

b) Spongy parenchyma: It is found below the palisade parenchyma tissue. Cells are almost spherical or oval and are irregularly arranged. Cells have intercellular spaces. It helps in gaseous exchange.

( iv) Vascular bundles: Vascular bundle are present in mid-rib and lateral veins. Vascular bundles are conjoint, collateral and closed. Each vascular bundle is surrounded by a sheath of Cuticle Palisade parenchyma Spongy parenchyma Lower epidermis Epidermal hair Stoma Bundle sheath Phloem Xylem Upper epidermis Figure . Transverse section of Dicot leaf parenchymatous cells called bundle sheath .

Each vascular bundle consists of xylem lying towards the upper epidermis and phloem towards the lower epidermis. . Internal Structure of Monocot Leaf (Isobilateral Leaf) Ex.Grass Leaf The transverse section of a monocot leaf reveals the following structures. (i) Epidermis: Monocot leaf has upper and lower epidermis.

Epidermis is made up of parenchyma cells. Cuticle is present on the outer wall stomata are present on both upper and lower epidermis. Some cells of upper epidermis are large and thin walled they are known as bulliform cells . (ii) Mesophyll: It is the ground tissue that is present between both epidermal layers.

Mesophyll is not differentiated into palisade and spongy parenchyma. The cells are irregularly arranged with inter-cellular spaces. These cells contain chloroplasts. (iii) Vascular bundles: Large number of vascular bundles are present, some of which are small and some are large.

. . Structure of Chloroplast Chloroplasts are green plastids containing green pigment called chlorophyll . Chloroplasts are oval shaped organelles having a diameter of - micrometer and a thickness of - micrometer.

Figure . Ultrastructure of Chloroplast Chloroplast DNA Starch granule Stroma Tylakoid Stroma lamella Inner membrane Outer membrane . Envelope: Chloroplast envelope has outer and inner membranes which is seperated by intermembrane space. .

Stroma: Matrix present inside to the membrane is called stroma. It contains DNA, S ribosomes and other molecules required for protein synthesis. . Thylakoids: It consists of thylakoid membrane that encloses thylakoid lumen.

Photosynthetic pigments are present in thylakoids. Thylakoids forms a stack of disc like structures called a grana (singular- granum). . Grana: Thylakoids arranged in the form of discs stacked one above the other called granum.

Grana are inter connected by stroma lamella. Bulliform cells Cuticle Upper epidermis Mesophyll Bundle sheath Xylem Phloem Lower epidermis Stoma Figure . Transverse section of Monocot Leaf Each vascular bundle is surrounded by parenchymatous bundle sheath. Vascular bundles are conjoint, collateral and closed.

Xylem is present towards upper epidermis and phloem towards lower epidermis. Table . Differences between of Dicot and Monocot Leaf S. No.

Dicot Leaf Monocot Leaf Dorsiventral leaf Isobilateral leaf Mesophyll is differentiated into palisade and spongy parenchyma Mesophyll is not differentiated into palisade and spongy parenchyma . Plant Physiology . . Plastids Plastids are double membrane bound organelles found in plants and some algae.

They are responsible for preparation and storage of food. There are three types of plastids. Chloroplast - green coloured plastids Chromoplast - yellow, red, orange coloured plastids Leucoplast - colourless plastids Plant Anatomy and Plant Physiology . .

Functions of Chloroplast . Photosynthesis . Storage of starch . Synthesis of fatty acids .

Storage of lipids . Formation of chloroplasts . . Photosynthesis Photosynthesis (Photo = light; synthesis = to build) is a process by which autotrophic organisms like green plants, algae and chlorophyll containing bacteria utilize the energy from sunlight to synthesize their own food.

In this process, carbon dioxide combines with water in the presence of sunlight and chlorophyll to form carbohydrates. During this process oxygen is released as a byproduct. 6CO + 12HO + HO chlorophyll Light C H O + 6O ↑ Carbon dioxide + Water Glucose + Oxygen + Water . .

Where does photosynthesis occur? Photosynthesis occurs in all green parts of the plant especially in green leaves. . .

Photosynthetic Pigments Pigments involved in photosynthesis are called Photosynthetic pigments. Photosynthetic pigments are of two classes namely, the primary pigments and accessory pigments. Chlorophyll a is the primary pigment that traps solar energy and converts it into electrical and chemical energy. Thus it is called the reaction centre.

Other pigments such as chlorophyll b and carotenoids are called accessory pigments as they pass on the absorbed energy to chlorophyll a (Chl.a) molecule. Reaction centre (Primary pigments) and harvesting centre (Accessary pigments) together form photo systems. . .