Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
vidan biology, profile picture
Uploaded byvidan biology
PDF, PPTX1,931 views

Tissue System in plant

The document discusses the tissue systems in plants, categorizing them into three main types: epidermal, fundamental (ground), and vascular tissues. It details the functions, characteristics, and components of these tissues, including stomata, trichomes, and cortical structures in roots and stems. Additionally, it describes various types of vascular bundles and their arrangements, highlighting their significance in plant structure and function.

Education◦
TISSUE SYSTEM
THE TISSUE SYSTEM Epidermal Fundamental or ground Vascular According to Sachs (1975) there are three main tissue systems: It performs manyfold function e.g., Protection, absorption, excretion, secretion, gaseous exchange and control of transpiration etc., Epidermis is generally uniseriate, i.e., composed of single layer of epidermal cells. These cells are of varying shapes and size and form a continuous layer inter irrupted by stomata. The tissue that do not come under epidermal tissue system or the vascular tissue system are regarded to constitute the fundamental or the ground tissue system. It constitute the main body of plant. The central cylinder of the shoot or root surrounded by cortex is called stele. The varying number of vascular bundles formed inside the stele constitute vascular tissue system. Each vascular bundle is made up of xylem and phloem with or without cambium.
• Deposition of cutin or suberin. Cutinization and subrization protects the epidermal cells from external mechanical injuries and retards transpiration. Epidermal cells in some monocot leaves, become larger thin walled, have vacuoles and are called bulliform (bubble like) cells. These cells bring about rolling of leaves during dry season. They loose water in dry season and contract thus bringing about rolling of leaves e.g., Ammophila thus reducing transpiration • Deposition of cutin or suberin. Cutinization and subrization protects the epidermal cells from external mechanical injuries and retards transpiration. Epidermal cells in some monocot leaves, become larger thin walled, have vacuoles and are called bulliform (bubble like) cells. These cells bring about rolling of leaves during dry season. They loose water in dry season and contract thus bringing about rolling of leaves e.g., Ammophila thus reducing transpiration
• Stomata In botany, a stoma, also called a stomate is a pore, found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the stomatal opening In botany, a stoma, also called a stomate is a pore, found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the stomatal opening Stomata
• Trichomes: from the Greek τρίχωμα (trichōma) meaning "hair", are fine outgrowths or appendages on plants, algae , lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant is an indumentum, and the surface bearing them is said to be pubescent. from the Greek τρίχωμα (trichōma) meaning "hair", are fine outgrowths or appendages on plants, algae , lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant is an indumentum, and the surface bearing them is said to be pubescent. •Trichomes: Papillary Filiform Branched Stellate
• In dicots stems and dicot and monocot roots (the ground tissues constitute the following parts: • (1) Cortex: The cortex when clearly delimited is the zone that lies between the epidermis and pericycle. It is differentiated into the following tissues: • (a) Hypodermis: In dicot stems below the epidermis there is one or more layered continuous or in patches collenchymatous tissue which is called hypodermis. In monocot stem it is sclerenchymatous. In plants where ridges and groove are found, collenchymatous hypodermis is present only below the ridges e.g., in Cucurbitaceae. Hypodermis is protective in function. • (b) General cortex: It may be few to many layered in thickness. The cells in most of the cases are thin walled and parenchymatous and may be rounded or polygonal or cylindrical. The cells have prominent intercellular spaces. Starch grain, oil, tannins and crystals of various types are some of the nonliving inclusions of cortical cells. • (c) Endodermis (Starch sheath): It is a single layer of compactly arranged cells which have distinctive wall characteristics The cells are living and may contain starch grains and mucilage. A special thickened band is present on radial and tangential walls of endodermal cells. This is called casparian strip. This is made up of lignin, suberin and cutin. • In dicots stems and dicot and monocot roots (the ground tissues constitute the following parts: • (1) Cortex: The cortex when clearly delimited is the zone that lies between the epidermis and pericycle. It is differentiated into the following tissues: • (a) Hypodermis: In dicot stems below the epidermis there is one or more layered continuous or in patches collenchymatous tissue which is called hypodermis. In monocot stem it is sclerenchymatous. In plants where ridges and groove are found, collenchymatous hypodermis is present only below the ridges e.g., in Cucurbitaceae. Hypodermis is protective in function. • (b) General cortex: It may be few to many layered in thickness. The cells in most of the cases are thin walled and parenchymatous and may be rounded or polygonal or cylindrical. The cells have prominent intercellular spaces. Starch grain, oil, tannins and crystals of various types are some of the nonliving inclusions of cortical cells. • (c) Endodermis (Starch sheath): It is a single layer of compactly arranged cells which have distinctive wall characteristics The cells are living and may contain starch grains and mucilage. A special thickened band is present on radial and tangential walls of endodermal cells. This is called casparian strip. This is made up of lignin, suberin and cutin.
(ii) Pericycle: It is a cylinder of thin walled parenchymatous or sometimes thick walled sclerenchymatous tissue (e.g., Cucurbita) ranging in width from a single layer of cells to a few layers. In some stems e.g., Sunflower, the pericycle is composed of alternating bands of thin walled and thick- walled cells (heterogenous pericycle). If it is made up of only one type of cells it is called homogenous pericycle. When composed of parenchymatous cells, it may act as storage region. In dicot roots the pericycle cells become meristematic and forms part of the cambium ring, Thick walled pericycle gives mechanical support to the plants. In angiosperms pericycle give rise to lateral roots. (iii) Medulla or pith: It occupies the central part in dicot stem and dicot and monocot roots. It is generally composed of large parenchymatous cells with intercept cellular spaces (sometimes sclerenchymatous). In most dicot roots the pith is completely obliterated by the metaxylem elements. In most dicotyledons the peripheral layers of pith extend between the vascular bundle and are in contact with pericycle. Cells of pith in this region are smaller and densely packed. These extensions are called pith rays or medullary rays. Pericycle Pith
3. Vascular (Fascicular) Tissue System Elements of a vascular bundle: The vascular bundles of a dicot stem are made up of the following elements: (a) Xylem: In dicotyledonous and monocotyledonous stem the development of xylem takes place towards periphery i.e., protoxylem is formed towards center and metaxylem towards the periphery. This is called centrifugal xylem and this condition is called endarch condition. (b) Phloem: In stem the phloem is away from the center towards the periphery and situated above the xylem. In dicotyledonous plants phloem is made up of sieve tubes, companion cells, phloem parenchyma' and phloem sclerenchyma. In monocotyledonous plants phloem is made up of sieve tubes, companion cells and phloem sclerenchyma. The phloem parenchyma is absent. Outer (peripheral) part of phloem is made up of narrow sieve tubes called protophloem and the inner part is meta phloem. (c) Cambium: A thin strip of primary meristem is present in between the xylem and phloem in dicotyledonous stems. It is called vascular cambium. The cambium cells are rectangular and
Conjoint Collateral Phloem Cambium Xylem Outer Phloem Outer cambium Xylem Inner cambium Inner phloem BiCollateral Open Closed • Types of Vascular bundles • (1) Conjoint: In stems the xylem and phloem are present on the same radius. Such vascular bundles are of two types: (a) Collateral: In this type of vascular bundles xylem is towards the inner side and phloem towards the outer periphery of xylem. In dicot stem cambium is present between xylem and phloem, such vascular bundles are called open. In monocot stems the cambium is absent, such vascular bundles are called closed (b) Bicollateral: In such vascular bundles there are two patches of phloem one on each side of xylem. In such a vascular bundles there are two strips of cambium one on each side of xylem. Thus the arrangement is outer phloem. outer cambium, xylem, inner cambium and inner phloem
(2) Concentric: In this vascular bundle either xylem surrounds the phloem or phloem surrounds the xylem. Concentric vascular bundles are of two types (a) Amphicribral (hadrocentric): The xylem is in the Centre surrounded by phloem (Fig. 15.35) e.g. Ferns. (b) Amphivasal (leptocentric): The xylem completely surrounds the phloem(Fig. 15.35) e.g., Dracaena, Yucca. (Fig. 15.35). Phloem Xylem Concentric AmphicribalAmphivasal Phloem Xylem(3) Radial: In roots there are separate and alternate strands of phloem and xylem that are separated by parenchymatous cells and are present on different radii such vascular bundles are called radial Radial (2) Concentric: In this vascular bundle either xylem surrounds the phloem or phloem surrounds the xylem. Concentric vascular bundles are of two types (a) Amphicribral (hadrocentric): The xylem is in the Centre surrounded by phloem (Fig. 15.35) e.g. Ferns. (b) Amphivasal (leptocentric): The xylem completely surrounds the phloem(Fig. 15.35) e.g., Dracaena, Yucca. (Fig. 15.35). (3) Radial: In roots there are separate and alternate strands of phloem and xylem that are separated by parenchymatous cells and are present on different radii such vascular bundles are called radial