[Music] chapter 6 anatomy of flowering plants you can very easily see the structural similarities and variations in the external morphology of the large living organism both plants and animals simil Sly if we were to study the internal structure one also find several similarities as well as differences this chapter introduces you to the internal structure and functional organization of higher plants study of internal structure of plant is called Anatomy plants have cells as the basic units cells are organized into tissues and in turn the tissues are organized into organs different organs in a plant show differences in their internal structure within angio spumps the monoc cords and diods are also seen to be anatomically different internal structures also show adaptations to diverse environments 6.1 the tissues a tissue is a group of cells having a common origin and usually performing a common function a plant is made up of different kinds of tissues tissues are classified into two main groups namely meristematic and permanent tissues based on whether the cells being formed are capable of dividing or not 6.1.1 meristematic tissues growth in plants is largely restricted to specialized regions of active cell division called Merry stems plants have different kinds of Merry stems the mer stems which occur at the tip of roots and shoots and produced primary tissues are called epical Mary stem root epical Mar stem occupies the tip of a root while the shoot epical Mary stems occupies the distant most region of the stem axis during the of leaves and elongation of a stem some cells Left Behind from Shoot epical Mery stem constitute the axillary butd such birds are present in the exils of leaves and are capable of forming a branch or a flower the Mery stem which occurs between mature tissues is known as interc calorie Mary stem they occur in grasses and regenerate Parts removed by the grazing hubby wordss both epical Mary stems and interc calor Mary stems are primary Mary stems because they appear early in life of a plant and contribute to the formation of a primary plant body the Marist stem that occurs in the mature regions of roots and shs of many plants particularly those that produce Woody AES and appear later than primary meristem is called a secondary or lateral meristem they are cylindrical meristems fular vascular cambium intravascular cambium and cor cambium are examples of lateral Mar stems these are responsible for producing the secondary tissues following divisions of cells in both primary and as well as secondary Mar stems the newly formed cells become structurally and functionally specialized and lose the ability to divide such cells are termed permanent or mature cells and constitute the permanent tissues during the formation of the primary plant body specific regions of the epical mar stem produce dermal tissues ground tissues and vascular tissues 6.1.2 permanent tissues the cells of the permanent tissues do not generally divide further permanent tissues having all cells similar in the structure and functions are called Simple tissues permanent tissues having many different types of cells are called complex tissues 6.1.2 point1 simple tissues a simple tissue is made of only one type of cells the various simple tissues in plants are parenchima called p enima and scena parena forms the major component within organs the cells of the parenchima are generally isodiametric they may be spherical oval round polygonal or elongated in shape their walls are thin and made up of cellulose they may be either they may either be closely packed or have a small intercellular spaces the parenchima performs various functions like photosynthesis storage secretion the colen Kima occurs in layers below the epidermis in most of the diot Lous plants it is found either as a homogeneous layer or in patches it consist of cells which are much thickened at the corners due to a deposition of cellulose hemicellulose and pectin colon chaus cells may be oval spherical or polygonal and often contain chloroplast these cell assimilate food when they contain chloroplast intercellular spaces are absent they provide mechanical support to the growing parts of the plants such as young stem and petol of leaf scarin Kima consist of long narrow cells with thick and lignified cell balls having a few or numerous pits they are usually dead and without protoplast on the basis of variation in form structure origin and development scarona may be either fibers or scarids the fibers are thick VA elongated and pointed cells generally occurring in groups in various parts of the plant the scleroids are spherical oval or cylindrical highly thickened dead cells with very narrow cavities that is Lumen these are commonly found in the fruit balls of nuts pulp of fruits like guava peer and sapota Seed coats of legumes and leaves of tea scarin Kima provides mechanical supports to organ 6.1.2 point2 complex tissue tissues the complex tissues are made of more than one type of cells and these work together as a unit xylm and flum constitute the complex tissues in Plants xylm functions as conducting tissue for water and minerals from Roots to the stem and leaves it also provides mechanical strength to the plant parts it is composed of four different kinds of elements namely tracks vessels xylem fibers and xylm parenchima gymnos sperms lack vessel in their XY tracked are elongated or tube like cells with thick and lignified walls and tapping ends these are dead and are without protoplasm the inner layers of the cell walls have thickening which vary in form in fling plants treds and vessels are the main water transporting elements vessel is a long cylindrical tube likee structure made up of many cells called vessel members each with lfi walls and a large Central cavity The Vessel cells are also devoid of protoplasm vessel members are interconnected through perforation in their common walls the presence of vessels is a characteristic feature of angos sperms xylem fibers have highly thickened walls and obliterated and obliterated Central lumens these May either be septate or asped xylm parenchima cells are living and thin walled and their cell walls are made up of cellulose they store food materials in the form of a starch or fat and other substances is like tenin the radial conduction of water takes place by the ray paryus cells primary xylm is of two types Proto xylm and metaz xylm the first formed primary xylm elements are called Proto xylm and the later formed primary xylm is called metaz xylm in a stems the Proto xylm lies towards the center that is pit and the metaz xylm lies towards the periphery of the organ this type of primary xylm is called in dark in Roots the Proto zym lies towards periphery and metaz xylm lies towards the center such arrangement of primary xylm is called Exar floam transports food materials usually from leaves to other parts of the plants floam in angiosperms is composed of SE tube elements companion cells flum parenchima and flum fibers gymnos spumps have albuminous cells and SE cells they lack SE tubes and companion cells SE tube elements are are also long tube like structures arranged longitudinally and are associated with the companian cells their end walls are perforated in a SE like manner to form the seeve plates a mature seeve element possesses a peripheral cytoplasm and a large vacu but lacks a nucleus the functions of SE tubes are controlled by the nucleus of companion cells the companion cells are specialized paryus cells which are closely associated with SE tu elements the SE tube elements and companion cells are connected by pit field present between their common longitudinal balls the companion cells help in maintaining the pressure gradient in the seep tubes flum parenchima is made up of elongated tapering cylindrical cells which have dense cytoplasm and nucleus the cell wall is composed of cellulose and has pits through which plasmo dust metal connection exist between the cells the fluent parena stores food material and other substances like raisins flum parena is made up of elongated tapering cylindrical cells which have dense cytoplasm and nucleus the cell ball is composed of cellulose and has pits through which plasmodesmal connection exist between the cells the fluent plan Kima stores food material and other substances like raisins lettu and mucilage floen parena is absent in most of the monoc corons flum fibers that is Bast fibers are made up of scarin katus cells these are generally absent in the primary flum but are found in the secondary floam these are much elongated unbranched and have pointed nle like epics the cell ball of flum fibers is quite thick at maturity these fibers loss their protoplasm and become dead flum fibers of Jud flax and hemp are used commercially the first form primary flum consist of narrow SE tubes and is referred to as Proto flum and the later formed flam has bigger SE tubes and is referred to as meta 6.2 the tissue system we were discussing types of tissues based on the types of cells present let us now consider how tissues were vary depending on their location in the plant body their structure and function would also be dependent on location on the basis of their structure and location there are three types of tissue systems these are the epidermal tissue system the ground or fundamental tissue system and the vesicular or conductive tissue system 6.2.1 epidermal tissue system the epidermal tissue system forms the outermost covering of the whole plant body and comprises epidermal cells stomata and the epidermal appendages the tricomes and hairs the epidermis is the outermost layer of the primary plant body it is made up of elongated compactly arranged cells which form a continuous layer epidermis is usually single layered epidermal cells are paryus with a small amount of cytoplasm lining the cell wall and a large vacu the outside of the epidermis is often covered with a waxy thick layer called the cuticle which prevents the loss of water cuticle is absent in Roots the stomata are structures present in the epidermis of leaves the stomata regulate the process of transpiration and gas G is exchange each sto is composed of two Bean shaped cells known as guard cells which enclose a stoal pore in grasses the guard cells are dumble shaped the outer wall of guard cells away from the stoal pore are thin and the inner walls that is towards the stomal pore are highly thickened the guard cells possesses chloroplast and regulate the opening and closing of a stomata sometimes a few epidermal cells in the vicinity of the guard cells become specialized in in their shape and size and are known as subsidiary cells the stomal aperal guard cells and the surrounding subsidiary cells are together called stoal apparatus the cells of epidermis bear a number of hairs the root hairs are unicellular elongations of the epidermal cells and help absorb water and minerals from the soil on the stem the epidermal hairs are called proms the tricomes in the shoot system are usually multicellular they may be branched or branched and soft or stiff they may even be SEC they may even be secretary the tricomes help in preventing water loss due to transpiration 6.2.2 the ground tissue system all tissues except epidermis and Vascular bundle constitute the ground tissue it consist of simple tissues such as parenchima colena and scena parena cells are usually present in cortex pericycle pit and medular Rays in the primary stems and roots in Le leaves the ground tissue consist of thin walled chloroplast containing cells and is called misop 6.2.3 the vascular tissue system the vascular system consists of complex tissues the flum and the xylm the xylm and flum together constitute vascular bundles in dious systems cambium is present between flum and xylm such vascular bundle because of the presence of cambium possesses the ability to form secondary xylm and flum tissues and hence are called vascular bundles in the monocoins the vascular bundles have no cambium present in them hence since they do not form secondary tissues they are referred to as closed when xylm and Plum within a vascular bundle are arranged in an alternate manner along the different radii the arrangement is called radial such as in Roots in conjoint type of vascular bundles the xylm and flum are jointly situated along the same radius of vascular bundles such vascular bundles are common in stems and leaves the conjoined vascular bundles usually have the flum located only on the outer side of xylm 6.3 anatomy of doradus and montilus plants for a better understanding of tissues organization of roots stem and leaves it is convenient to study the transverse sections of the mature zones of these organs 6.3.1 dorus rout it shows the transverse section of the sunflower route the internal tissue organization is as follows the outermost layer is epma many of the cells of epma protrude in the form of unicellular root hairs the cortex consist of several layers of thin walled parenchima cells with intercellular spaces the innermost layer of the cortex is called endodermis it comprises a single layer of barrel shaped cells without any intercellular spaces the tangential as well as radial walls of the endoderm cells have a deposition of water impermeable vxi material subaran in the form of Casper and strips next to endodermis lies a few layers of thick balled paryus cells referred to as pericycle initiation of lateral roots and Vascular cambium during the secondary growth takes place in these cells the pit is a small or inconspicious the paryus cells which lie between the xylm and the flum are called conjunctive tissue there are usually two to four xylm and flum patches later a cambium ring develops between the xylm and flum all tissues on the inner side of the endodermis such as pericycle vascular bundles and pit constitute the steel 6.3.2 monarus root the anatomy of the monocot root is similar to The diot Root in many respects it has epidermis cortex endodermis pericycle vascular bundles and pit as compared to the diot root which have fewer xylm bundles there are usually more than six that is poly Arch xylm bundles in the monocot rout pit is large and welldeveloped monocot ladness Roots do not undergo any secondary growth 6.3.3 dadness stem the transfers section of a typical young dcot ladness stem shows that the epidermis is the outermost protective layer of the stem covered with a thin layer of cuticle it may be a tricomes and a few stomata the cells arranged in multiple layers between epidermis and pericycle constitute the cortex it consist of three subzones the outer hypodermis consist of a few layers of Colonus cells just below the epidermis which provide mechanical strength to the young stem cortical layers below hypodermis consist of rounded thin VA paren cells with conspicious intercellular spaces the innermost layer of the cortex is called the endodermis the cells of the endodermis are rich in a starch grain and the layer is also referred to as starch sheath pericycle is present on the inner side of the endodermis and above the flam in the form of semilunar patches of a scler enima in between the vascular bundles there are few layers of radially placed paryus cells which constitute medular Rays a large number of vascular bundles are arranged in a Ring The Ring arrangement of vascular bundles is a characteristic of diot stem each vascular bundle is conjoined open and with end dark Proto zym a large number of rounded Paratus cells with large intercellular spaces which occupy the central portion of the stem constitute the pit 6.3.4 monoc cortius stem the monocord stem has a scarin chatus hypodermis a large number of scattered vascular bundles each surrounded by a scarin chatus bundle sheath and a large conspicious Paratus ground tissue vascular bundles are conjoined and closed peripheral vascular bundles are generally smaller than the centrally located ones the flum parena is absent and water containing cavities are present within the vascular bundles 6.3.5 dorsy ventral that is D cotus Leaf the vertical section of Dy ventral Leaf through the lamina shows three main parts namely epidermis misop and vascular system the epidermis which covers the both the upper surface that is adaxial epidermis and lower surface that is abaxial epidermis of the leaf has a conspicious cuticle the abaxial epidermis generally bear more stomata than the adaxial epidermis the later may even lack stomata the tissue between the upper and the lower epidermis is called the mop misop which possesses chloroplast and carry out photosynthesis is made up of parena it has two types of cells the piset parenchima and the spongy parena the adaily placed piset parena is is made up of elongated cells which are arranged vertically and parallel to each other the oval or round and Loosely arranged spongy parena is situated below the piset cells and extend to the lower epidermis there are numerous large spaces and air cavities between these cells vascular system includes vascular bundles which can be seen in the veins and the mid rib the size of the vascular bundles are dependent on the size of the veins the veins vary in thickness in the reticulate venish of the dcot leaves the vascular bundles are surrounded by a layer of thick wall bundle sheath cells 6.3.6 isobilateral that is monoc cotus leaf the anatomy of isobilateral leaf is similar to that of the dorsy ventral Leaf in many ways it shows the following characteristic differences in an isobilateral Leaf the stomata are present on both the surface of the epidermis and the misop is not differentiated into PISD and SP parena in grasses certain adaxial epidermal cells along the veins modify themselves into large empy colorless cells these are called bully form cells when the bully form cells in the leaves have absorbed water and are TG it the leav surface is exposed when they are flaccid due to water strad they make the leaves curls inward to minimize water loss the parallel vation in monocot leaves is reflected in the near similar sizes of vascular bundles except in main veins as seen in vertical sections of the leaves 6.4 secondary growth the growth of the roots and the stem in length with the help of epical maryem is called the primary growth apart from the primary growth most died cadness plants exhibit an increase in girth this increase is called the secondary growth the tissues involved in secondary growth are the two lateral Mery stems vascular cambium and C cambium 6.4.1 vascular cambium the meristematic lay that is responsible for cutting of vascular tissues xylm and flum is called vascular cambium in the young stem it is present and patches a single layer between the xylm and flum later it forms a complete ring 6.4.1 point1 formation of cambial ring in dcot stems the cells of cambium present between primary xylm and primary flum is the intrafascicular cambium the cells of our medular Rays at joining these intrafascicular cambium become meristematic and form the intravascular cambium and form the intervascular cambium thus a continuous ring of cambium is formed 6.4.1 point2 activity of the cambial Ring The cambial Rim becomes active and begins to cut off new cells both towards the inner and the outer sides the cells cut off towards pit mature into secondary xylm and the cells cut off towards periphery mature into secondary flum the cambium is generally more active on the inner side than on the outer as a result the amount of secondary xylm produced is more than secondary flum and soon forms a compact Mass the primary and secondary fls get gradually crushed due to continued formation and accumulation of secondary xylm the primary xylm however remains more or less intact in or around the center at some places the cambium forms a narrow band of parena which passes through the secondary xylm and the secondary plum in the radial directions these are the secondary medular Rays 6. 4.1.3 spring wood and Autumn Wood the activity of cambium is under the control of many physiological and environmental factors in temperate regions the climatic conditions are not uniform through the year in the spring season cambium is very active and produces a large number of XY elements having vessels with wider cavities the wood formed during this season is called a spring wood or early wood in Winter the cium is less active forms fewer xary elements that have narrow vessels and this wood is called Autumn Wood or late wood the spring wood is lighter in color and has a lower density whereas the Autumn Wood is darker and has a higher density the two kinds of woods that appear as alternate concentric Rings constitute an annual ring annual rings seen in a cut stem given an estimate of the age of the tree 6.4.1 point4 hardwood and sapwood in Old trees the greater part of of secondary xylem is dark brown due to deposition of organic compounds like tannins raisins oils gums aromatic substances and essential oils in the central or innermost layers of the stem these substances make it harder durable and resistant to the attacks of microorganism and insects this region comprises dead elements with highly lagifi balls and is called hardwood the hardwood does not conduct water but it gives mechanical support to the stem the per pereral region of the secondary xylm is lighter in color and is known as the sapwood it is involved in the conduction of water and minerals from root to Leaf 6.4.2 core cambium as the stem continues to increase and girth due to the activity of vascular cambium the outer cortical and epidermis layer get broken and need to be replaced to provide new protective cell layers hence sooner or later another meristematic tissue called cor cium or felen develops us usually in the cortex region Fen is a couple of layers thicks it is made of a narrow thin VA and nearly rectangular cells Fen cuts off cells on both sides the outer cells differentiate into cork or fum while the inner cells differentiate into secondary cortex or fodm the cork is imperious to water due to subaran deposition in the cell wall the cells of secondary cortex are parentis felen fum and fodm are collectively known as periderm due to to activity of the co cambium pressure builds up on the remaining layers peripheral to Fen and ultimately these layers dies and slow off bark is non-technical term that refers to all tissues exterior to the vascular cambium therefore including secondary flum bar refers to a number of tissues type perid and secondary flum bar that is formed early in the season is called early or soft bar towards the end of season late or hard bark is formed name the various kinds of cell layers which constitute the bath at certain regions the fen cuts off closely arranged parenchima cells on the outer side instead of Co cells these paryus cells soon rupture the epidermis forming a lens shaped opening called lenticles lenticles permit the exchange of gases between the outer atmosphere and the internal tissues of the system these occur in most Woody trees in the D 6.4.3 secondary growth in Roots in the dcot route the vascular cambium is completely secondary in origin it originates from the tissue located just below the flum bundles a portion of pericycle tissue above the protoy forming a complete and continuous wavy ring which later becomes circular further events are similar to those already described above for doriden stem secondary growth also occurs in stems and roots of gymnos sperms however secondary growth does not occur in monoar summary anatomically a plant is made of different kinds of tissues the plant tissues are broadly classified into meristematic that is epical lateral and Inter calorie and permanent that is simple and complex assimilation of food and its storage transportation of water minerals and photosynthe and mechanical support are the main functions of tissues there are three types of tissue system epidermal ground and Vascular the epidermal tissue system are made of epidermal cells the stomata and epidermal appendages the ground tissue system forms the main bulk of the plant it is divided into three zones cortex pericycle and pit the vascular tissue system is formed by the xylm and flum on the basis of the presence of cambium location of xylem and flam the vascular bundle are different types the vascular bundles form the conducting tissue and translocate water minerals and food material monoc Corti and doradus plants show marked variation in their internal structures they differ in type number and location of vascular bundles the secondary growth occurs in most of the doradus roots and stems and it increases the girth that is diameter of the organs by the activity of vascular cambium and the cambium the wood is actually a secondary xylm there are different types of woods on the basis of their composition and time production chapter completed thank you