Std. 11 Morphology of flowering parts complete.pdf

Unit 2. Morphology of the Flowering Plants MORPHOLOGY OF ROOT Root is the non-green part of plant which grows in the soil. Characteristics of roots 1. The root develops from the radicle of the embryo present in the seed. 2. It grows downwards into the soil away from light...

Unit 2. Morphology of the Flowering Plants MORPHOLOGY OF ROOT Root is the non-green part of plant which grows in the soil. Characteristics of roots 1. The root develops from the radicle of the embryo present in the seed. 2. It grows downwards into the soil away from light (Negatively phototropic). 3. It is non-green and cannot synthesise organic food. 4. At the apex of the root is the root cap. 5. Numerous unicellular root hair are present near the tips 6. To increase surface for absorption of water and minerals. Functions of Roots a. Anchorage: The roots anchor or fix the plant to the substratum or soil. b. Absorption: Roots absorb water and minerals from soil with the help of root hair. c. Conduction: Roots transport absorbed water and minerals to the stem through xylem. 1 Roots Systems There are two kinds of root systems, the root system and the adventitious root system. Tap Root System ▪ It develops from the radicle of germinating seed. The radicle grows to from the primary or the tap root. It branches to from the as secondary roots or tertiary roots. ▪ The tap root with its branches constitutes the tap root system. E.g. dicot plants ▪ Tap roots are normally deep feeders. Adventitious Root System It develops from any part of the plant other than the radicle. Like base of stem, nodes of the stem as in Banyan tree and Mangroves or from foliar buds as in Bryophlyllum. e.g. In monocotyledons, the primary tap root is short-lived and is replaced by a number of fibrous roots, called the adventitious roots. A cluster of slender, adventitious roots along with the branches is called the fibrous root system. It is commonly found in monocot plants like maize, sugarcane, wheat, etc. Modifications of Roots Modification of Tap Roots 1. Storage Roots : In some plants, primary root becomes thick and fleshy to the storage of food. The fleshy tap roots are of the following types: a) Conical : e.g. Carrot b) Fusiform : e.g. Radish c) Napiform : e.g. Beetroot 2  2. Respiratory or Breathing Roots : Normally, roots get air for respiration from small spaces between the soil particles. But in marshy places, soil becomes saturated with water and aeration of the soil becomes impossible. In such cases, uprights roots arise from the ordinary roots lying buried in the saline swamps and marshes. These roots are called pneumatophores. In Sonneratia and Avicenna. Modifications of Adventitious Roots 1. Roots Modified for Storage of Food a. Tuberous Roots: The Stem of some plants is creeping with adventitious roots arising from the nodes. Some of these roots become swollen and develop into root tubers. E.g. Sweet potato 3  2. Roots Modified for Additional Support ▪ Prop Roots : These arise from the branches and grow vertically downwards into the soil. They bear lenticels for action, e.g. Banyan tree ▪ Stilt Roots or Brace Roots : These roots arise from first few nodes of the stem in whorls. These penetrate obliquely onto the soil and give support to the plant, e.g. Maize, Surgarcane, Bamboo. MOROOPHOLOGY OF STEM Stem is the prolongation of plumule of the embryo and forms main axis of the plant. Characteristics of Stem The stem forms the main axis of the plant Develops from the plumule. It is negative geotropic and positively phototropic It has well-marked odes and internodes. The young stem is green in colour and is thus photosynthetic. The growing apex of stem bears a terminal bud. 4 Functions of Stem 1. Primary Functions a. It supports leaves and branches and holds them to provide maximum light. b. It conducts water and minerals from roots to the leaves and synthesised food from leaves to the roots and storage organs. c. It beans flowers and fruits. Modifications of Stem 1. Underground Stems: These stems are nongreen, and perennial. They store reserve food, carry propagation vegetatively and are adapted for perennation during the unfavourable conditions. The underground stems resemble roots, but differ from roots in: 1. The presence of nodes and internodes. 2. The presence of scale leaves ad adventitious roots arising from the nodes. 3. The presence of axillary and terminal buds. 1. Rhizome : The rhizomes are shout, horizontal and thick underground steams. Because of excessive storage of food material. e.g. Ginger, Turmeric 2. Tubers: Tubers are swollen ends of special underground branches of stem. Potato is the best known example. It bears buds in small pits known as eyes. 3. Bulb : in bulbs, stem is shortest and somewhat disc-like. It does not contain any food material. Stem is covered by numerous thickened, overlapping leaves or leaf bases usually called scales. The short and reduced stem bears numerous adventitious roots at its base: a. Tunicated Bulbs: In this case, fleshy scales completely surround the reduced stem forming concentric layers around one another. On the outside, they are covered by a few dry scales forming a membranous covering, called the tunic. The fleshy scales are bases of the foliage leaves, e.g... Onion, Narcissus. Tulipa, etc. b. Scaly Bulbs: These bulbs have small and scale-like leaves with overlapping margins. There is no outer tunic. The scaly bulbs are found in Lillies, Garlic, etc. In both the above types, axillary buds arise in the axil of fleshy scales. These develop into new bulbs or on separation 5  from the parent bulb develop into plants. They serve both for food storage and vegetative propagation 4. Corm: It is more or less a condensed form of rhizome. It is a short, stout, solid, rounded and fleshy underground stem growing in vertical direction. Some of these buds grow up into aerial flowering shoots and adventitious roots arise from their base. 2. Subaerial Steams: Such stems are found in plants with a thin, delicate and weak stem. A part of the stem lives underground whereas remaining part of the stem is aerial These plants bear adventitious roots and aerial branches at nodes. 1. Runner: A runner as long and thin internodes. Creep over the surface of soil. Runners grow in all directions from mother plant. Daughter plants propagate in the same manner. Ex. Doob grass 2. Stolon: It develops from under-ground stems. It grows horizontally outwards and bears nodes and internodes. Ex. Strawberry. 3. Sucker: It is a modified under-ground runner. It originates as a lateral branch from the underground axillary bud of an aerial shoot. It travels obliquely underground for some distance and then grows upwards. Ex. Mint 4. Offset : It is also known as condensed runners. Unlike a runner, an offset produces at the apex a tuft leaves above a cluster of roots below. 6  On breaking off from the parent plant, each branch forms an independent plant. Ex. Water hyacinth (Eichhornia). 3. Aerial or Epiterranean stems : In some plants, stem undergoes an extreme degree of modification to perform degree certain special functions 1. Stem Tendrils : There are highly specialised climbing organs of the plants. They are thin, wiry and spirally – coiled branches. On coming in contact with a neighbouring object, the tendrils coil around it and help the plant to climb. 2. Stem Thorns: there are stiff, sharp structures that develop in place of stem branches. Thorns check water loss by transpiration and also protect the plant from browsing animals, e.g. Bougainvillea 3. Phylloclades: there are green stems of unlimited growth that have taken over the function of photosynthesis. Help the plant to grow in dry habitats because of and reduced transpiration from the stem. E.g. Opuntia. 4. Cladodes (chlorophylls): These are green stems of limited growth. These true leaves are reduced to scales or spines. E.g. Asparagus. 7 MOROPHOLOGY OF LEAF The leaf is a thin flattened, green outgrowth of the steam or his branch, borne at a node and having a bus in its axil. Characteristics of a Leaf An axillary bud is always present in the axil of a leaf. Its growth is limited. Leaf lamina is traversed by prominent vascular strands called veins. 8 Functions of leaf 1. Primary Functions : 1. Photosynthesis: Leaves manufacture organic food by the process of photosynthesis. Due to the presence of green pigment, the chlorophyll. 2. Exchange of Gases: stomata present on the leaf surface help in the exchange of gases necessary for photosynthesis and respiration. 3. Transpiration: Stomata assist in transpiration which helps in the ascent of sap and also in keeping the leaf surface cool. 4. Conduction of Water and Food: the vascular elements in the veins and petiole help in the conduction of water and minerals form the stem to the lamina and organic food from lamina to the stem. 2. Secondary Functions a. Storage of food and water: vegetative Function : In Bryophyllum and Begonia, leaves bear adventitious buds and help on vegetative propagation. Parts of Leaf A typical leaf has three main parts: 1. Petiole (Mosopodium) : Petiole connects lamina with the stem or branch. A left is said to be sessile if the petiole is absent as in wheat. 2. Leaf blade of lamina (Epipodium) This is the most important, green and flattened part of the leaf which is mainly concerned with manufacture of food. Lamina is traversed medially from base of the apex by the midrib From which arise numerous thin lateral veins, and still thinner veins or veinlets. Venation The arrangement of veins and veinlets in the leaf lamina is called venation. 9 Of two types : Reticulate and parallel 1. Reticulate Venation : it is found in dicot leaves. In this type of venation, main vein divides into branches to form a bet-like structure in the lamina. Parallel Venation: In this case, all veins run parallel to each other. Most of the monocot leaves have this type of venation. Stipules: Leaf base bears two lateral appendages called the stipules. Such leaves are called stipulate. The leaves without stipules are called exstipulate. Stipules provide protection. Phyllotaxy: Arrangement of leaves on the stem and branches is called phyllotaxy. 1. Alternate: When a single leaf arises at each node, it is called alternate or spiral phyllotaxy. Examples: Mango, China rose 2. Opposite: Two leaves are present at each node, standing opposite to each other. Examples: Ocimum, Jamun (Eugonia jambolana), Rangoon creeper (Quis quails). 3. Whorled: More than two leaves are present in a whorl at each node, e.g. Oleander (Nerium), Alstonia, etc. 10 Types of Leaves: 1. Simple Leaf : In a simple leaf, the lamina is not broken up into seprate lobes or leaflets. The leaves of Banyan, Mango, Ficus, etc. are simple leaves. 2. Compound Leaf: In the compound leaf, the lamina is divided up to midrib or petiole, into a number of leaf-like lobes called leaflets these leaflets are borne on a common axis called rachis (or rachis). The leaflets do not bear any axillary bud in their axil. a. Pinnate Compound or Simple Leaves: In such leaves, rachis is elongated and bears two rows of simple of divided leaflets. E.g. Tamarind, Rose and Neem. b. Palmate Compound Leaves: All the leaflets are attached at a common point at the tip of the petiole. These leaflets may be petiolate or sessile. E.g. Citrus, Lemon, Clover. 11 Modification of Leaf 1. Leaf Tendrils: they are slender, Mechanical supports structures. For Mechanical supports They are climbing organs and sensitive to contact with a foreign body. 2. Leaflet-hooks: For mechanical support Leaves become, stiff, curved and claw- like hooks. These cling to the support firmly and help the plant to climb. 3. Pitcher: ❖ In Nepenthes, (Pitcher Plant), whole leaf is modified into a pitcher, the upper surface of the leaf occupying the inner surface of the pitcher. ❖ The apex of the leaf forms the lid. The function of pitcher is to capture and digest insects. Such plants are known as insectivorous plants. ❖ In Dionea (Venus fly trap), bilobed leaves are hinged to perform the function of catching insects. 12 MORPHOLOGY OF FLOWER INFLORESCENCE ❖ Flowers are borne either singly or in clusters. ❖ A flower is said to be solitary when occurring singly. ❖ Solitary Flowers: The solitary flowers may be terminal or axillary. ❖ It present in clusters, they constitute an inflorescence. ❖ The arrangement and distribution of flowers on the floral axis is termed is termed as inflorescence. The floral axis or stalk bearing an inflorescence is called peduncle. A flat peduncle is known as receptacle. Types of inflorescence In florescence is of types - Racemose, Cymose 1. Racemose Inflorescence It is indeterminate or indefinite inflorescence in which peduncle or main axis continues to grow indefinitely and is not terminated into a flower. It gives off flowers on lateral sides to grow indefinitely and is not terminated into a flower. It gives off flowers on lateral sides in acropetal manner, i.e. the lower or outer flowers are older that the upper or inner flowers. E.g. Mulberry, Cherry. 2. Cymose Inflorescence The primary axis or peduncle terminates in flower but the growth continues through the lateral buds. These buds give rise to lateral branches which bear flowers. The flowers are arranged in basipetal or centrifugal succession. E.g. Jasmine, Calotropic. 13  THE FLOWER Flower is a condensed. Specialised shoot of an Angiospermic plant Because of the presence of flowers, angiosperms are called flowering plants. Flower arises in the axil of a small leaf-like structure, the bract. The Flower us commonly borne on a short on long pedicel. The upper swollen region of pedicel is called receptacle or thalamus. Flowers having a pedicel are called pedicellate. Flowers without a pedicel are called sessile. Parts of a Flower A typical flower consists of four Horal whorls on the receptacle or thalamus. They are Calyx, Corolla Androecium and Gynoecium. 1. Calyx: It is the outermost whorl of the flower. It is composed of leaf-like green sepals. Sepals enclose the bud and protect the delicate parts within. 2. Corolla: It is the second whorl of the flower, and consists of a number of petals. In majority of flowers, petals are brightly coloured, scented and are of various shapes They attract insects for pollination. 3. Androecium: This is the third whorl of flower and is the male reproductive organ consisting of stamens. Each stamen is made of three parts: filament, anther and connective. 14  The filament is a part of stamen that supports anther at its tip. The anther is four- chambered and bears granular mass of pollen grains. The connective joins two anther lobes. Since each stamen is considered to be a highly modified leaf, it is termed as microsporophyll. 4. Gynoecium: This is the fourth whorl of flower and is female reproductive organ of the flower. It is known as pistil. It occupies central position on the receptacle and is composed of vary, style and stigma and these component parts are called carpels. Ovary encloses egg-like bodies, the ovules. The stigma is sticky and receives pollen. Ovules form the seeds after fertilisation and ovary becomes the fruit. Taxonomic Description of Flower The sepals and petals are not directly involved in the reproduction. They are called the accessory or non-essential whorls, whereas androecium and gynoecium called are necessary or essential or reproductive whorls because they take part in reproduction. Bisexual: When stamens and carpels are found in the same flower. Such flowers are also called hermaphrodite, i.e., China Rose. Pea, etc. Unisexual: When only one of the essential whorls is found in a flower, ie., either androecium or gynoecium, e.g.. Cucurbits, Mulberry, etc. Complete and Incomplete Flowers 15  Complete Flowers: Flowers having all the four floral whorls. E.g. China Rose, Cotton etc. Incomplete Flowers: In such flowers, out of the four whorls any one of whorl is absent, e.g., Cucurbits. Symmetry in Flowers The arrangement of floral appendages on the axis of a flower is called floral symmetry. The axis to which flower is attached is called mother axis. Actinomorphic or Regular: Such a flower can be divided by any vertical plane into two equal and similar halves. Examples: Mustard, Brinjal, Catharanthus. Rose, Shoe-flower. Zygomorphic or Irregular: Such a flower can be divided into two equal halves by only one vertical plane. Examples: Pea, Larkspur, Ocimum. 16 Isomerous and Heteromerous Flowers A flower is isomerous when there is the same basic number of parts in different floral organs. Isomerous flowers may be bimerous, trimerous, tetramerous or pentamerous according to the number of parts in each whorl, i.e., 2, 3, 4, 5 or any multiple of it. When number in all the whorls is neither the same nor any multiple, the flower is said to be heteromerous. Dicot flowers are usually di-, tetra or pentamerous whereas monocot flowers are trimerous. Hypogynous, Perigynous and Epigynous Flowers: Depending upon the form of thalamus and the position of floral whorls on the thalamus with respect to ovary, flowers are of following three types: Hypogynous: The thalamus is convex and ovary occupies the highest position on it. The outer three whorls viz. sepals, petals and stamens are inserted one above the other but below the ovary. Since the ovary lies above all the other parts, it is described as superior and the rest of the floral whorls as inferior. Examples: Brinjal, China Rose Perigynous: The receptacle or the thalamus forms a shallow or deep cup-shaped structure around the ovary. The ovary is superior. Cup-shaped- Thalamus. Gynoecium grows from the bottom of the cup while other floral whorls are borne at the rim of thalamus. The ovary is superior. Epigynous: Thalamus not only surrounds the ovary completely but also encloses it and fuses with the ovary wall. The sepals, petals and stamens arise from the top of the ovary. Such flowers are said to be epigynous. The ovary in these flowers is inferior and the other whorls are superior. Examples: Apple, Sunflower, etc. 17 Corolla or Petals It is the second whorl of flower present inner to calyx and made up of petals. Corolla protects the essential whorls, stamens and carpels. Petals are variously coloured. If the petals are free from one another, the corolla is polypetalous, and if there is any degree of fusion between the petals, it is gamopetalous. Like calyx, corolla may be caducous, mostly deciduous and rarely persistent. Aestivation of Sepals and Petals The mode of arrangement of petals and sepals in relation to one another in a flower bud is known as aestivation. Valvate: When the petals lie close to each other or simply touch each other, i.e., neither overlap the margin of the adjacent petal nor overlapped by the margin of the adjacent petal, e.g.. Calotropis. Twisted or Contorted: In this case, one margin of a petal covers the margin of the adjacent petal and the other margin is covered over by the margin of adjacent petal. e.g., Lady's finger, hibiscus) Imbricate: In this case, there is irregular overlapping of petals. Eg. Descending Imbricate or Vexillary: Posterior petal overlapping the two lateral petals, the lätter overlapping the two anterior petals. It is also called papilionaceous, e.g., Pea. 18 Perianth: When there is no distinction in sepals and petals, the two whorls are collectively called perianth. The individual parts of perianth are called tepals. When green, they are called sepaloid and when coloured petaloid, When tepals are free they are called polyphyllous and if united gamophyllous. Androecium or Stamens Stamens are male reproductive organs of a flower. A stamen consists of a slender stalk- like filament and a knob-like anther. Each anther has two lobes. Each anther lobe has two pollen sacs (= microsporangia). They contain pollen grains (= microprocess). Cohesion of Stamens 1. Monadelphous: Filaments of all stamens are fused to form a tube-like structure, e.g., Hibiscus. 2. Diadelphous: Filaments of all the stamens are fused in two groups, e.g., Pea 3. Polyadelphous: When filaments are united in more than two groups, e.g., Citrus. 4. Syngenesious: When anthers of all the stamens are fused and filaments are free,e.g., Ageratum Sunflower, Sonchus 5. Synandrous: When all the anthers as well as filaments are united to form a compound structure., e.g., Cucurbita. 19 Adhesion of Stamens 1. Epipetalous: Stamens are fused with petals, e.g., Petunia. 2. Epiphyllous or Epitepalous: Stamens are fused with petal-like perianth-lobes, e.g.Asphodelus. Gynoecium Or Pistil Gynoecium or pistil is the female reproductive whorl of flower. A pistil may comprise one to several carpels. Each carpel represents one megasporophyll. Locules of the Ovary: Ovary is the basal swollen part containing ovules. Depending on the number of locules, ovary may be: 20  1. Unilocular with one locule, e.g. Pea. 2. Bilocular with two locules, e.g Mustard. 3. Multilocular with many locules, e.g., Althaea. In the locules or chambers are present oval outgrowths called ovules attached to a flattened cushion-like tissue called placenta. Ovules on fertilisation form seeds and the wall of the ovary forms pericarp. Cohesion of Carpels: The carpels may be two, or more and may be free or fused. The free condition of carpels is called apocarpous. The fused condition of carpels is known as syncarpous. When the carpels are fused by their stigmas (Calotropis) or stigma and style (Oleander) the carpels are said to be apocarpous. Functions of Flower 1. Flower is a modified shoot specialised to perform sexual reproduction in angiosperms. 2. It possesses coloured petals for attracting pollinating agents. 3. It often possesses edible pollens or nectaries for feeding the visiting pollinators. 4. It possesses green sepals or calyx to protect and support the internal delicate floral in the bud stage. 21 5. It takes part in the formation of fruit after fertilisation. 22