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UNIT 2, STRUCTURAL ORGANISATION, IN PLANTS AND ANIMALS, Chapter 5, Morphology of, Flowering Plants, Chapter 6, Anatomy of Flowering, Plants, Chapter 7, Structural Organisation in, Animals, , The description of the diverse forms of life on earth was made only by, observation – through naked eyes or later through magnifying lenses, and microscopes. This description is mainly of gross structural features,, both external and internal. In addition, observable and perceivable, living phenomena were also recorded as part of this description. Before, experimental biology or more specifically, physiology, was established, as a part of biology, naturalists described only biology. Hence, biology, remained as a natural history for a long time. The description, by itself,, was amazing in terms of detail. While the initial reaction of a student, could be boredom, one should keep in mind that the detailed description,, was utilised in the later day reductionist biology where living processes, drew more attention from scientists than the description of life forms, and their structure. Hence, this description became meaningful and, helpful in framing research questions in physiology or evolutionary, biology. In the following chapters of this unit, the structural organisation, of plants and animals, including the structural basis of physiologial or, behavioural phenomena, is described. For convenience, this description, of morphological and anatomical features is presented separately for, plants and animals., , 2021-22
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Katherine Esau, (1898 – 1997), , KATHERINE ESAU was born in Ukraine in 1898. She studied, agriculture in Russia and Germany and received her doctorate, in 1931 in United States. She reported in her early publications, that the curly top virus spreads through a plant via the foodconducting or phloem tissue. Dr Esau’s Plant Anatomy published, in 1954 took a dynamic, developmental approach designed to, enhance one’s understanding of plant structure and an, enormous impact worldwide, literally bringing about a revival, of the discipline. The Anatomy of Seed Plants by Katherine Esau, was published in 1960. It was referred to as Webster’s of plant, biology – it is encyclopediac. In 1957 she was elected to the, National Academy of Sciences, becoming the sixth woman to, receive that honour. In addition to this prestigious award, she, received the National Medal of Science from President George, Bush in 1989., When Katherine Esau died in the year 1997, Peter Raven,, director of Anatomy and Morphology, Missouri Botanical, Garden, remembered that she ‘absolutely dominated’ the field, of plant biology even at the age of 99., , 2021-22
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C HAPTER 5, MORPHOLOGY OF FLOWERING PLANTS, 5.1 The Root, 5.2 The Stem, 5.3 The Leaf, 5.4 The Inflorescence, 5.5 The Flower, 5.6 The Fruit, 5.7 The Seed, 5.8 Semi-technical, Description of a, Typical, Flowering Plant, 5.9 Description of, Some Important, , The wide range in the structure of higher plants will never fail to fascinate, us. Even though the angiosperms show such a large diversity in external, structure or morphology, they are all characterised by presence of roots,, stems, leaves, flowers and fruits., In chapters 2 and 3, we talked about classification of plants based, on morphological and other characteristics. For any successful attempt, at classification and at understanding any higher plant (or for that, matter any living organism) we need to know standard technical terms, and standard definitions. We also need to know about the possible, variations in different parts, found as adaptations of the plants to their, environment, e.g., adaptions to various habitats, for protection,, climbing, storage, etc., If you pull out any weed you will see that all of them have roots, stems, and leaves. They may be bearing flowers and fruits. The underground, part of the flowering plant is the root system while the portion above the, ground forms the shoot system (Figure 5.1)., , Families, , 5.1 THE ROOT, In majority of the dicotyledonous plants, the direct elongation of the radicle, leads to the formation of primary root which grows inside the soil., It bears lateral roots of several orders that are referred to as secondary,, tertiary, etc. roots. The primary roots and its branches constitute the, , 2021-22
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66, , BIOLOGY, , Flower, , Fruit, Stem, Leaf, , Shoot, system, , Node, Internode, , {, , Bud, , Primary, root, Root, Secondary system, root, , tap root system, as seen in the mustard, plant (Figure 5.2a). In monocotyledonous, plants, the primary root is short lived and, is replaced by a large number of roots., These roots originate from the base of the, stem and constitute the fibrous root, system, as seen in the wheat plant (Figure, 5.2b). In some plants, like grass,, Monstera and the banyan tree, roots arise, from parts of the plant other than the, radicle and are called adventitious roots, (Figure 5.2c). The main functions of the, root system are absorption of water and, minerals from the soil, providing a proper, anchorage to the plant parts, storing, reserve food material and synthesis of, plant growth regulators., , Figure 5.1 Parts of a flowering plant, , Main root, , Laterals, , Fibrous roots, , (a), , (b), , Adventitious roots, , (c), , Figure 5.2 Different types of roots : (a) Tap (b) Fibrous (c) Adventitious, , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 5.1.1, , 67, , Regions of the Root, , The root is covered at the apex by a thimble-like, structure called the root cap (Figure 5.3). It, protects the tender apex of the root as it makes, its way through the soil. A few millimetres above, the root cap is the region of meristematic, activity. The cells of this region are very small,, thin-walled and with dense protoplasm. They, divide repeatedly. The cells proximal to this, region undergo rapid elongation and, enlargement and are responsible for the growth, of the root in length. This region is called the, region of elongation. The cells of the elongation, zone gradually differentiate and mature. Hence,, this zone, proximal to region of elongation, is, called the region of maturation. From this, region some of the epidermal cells form very fine, and delicate, thread-like structures called root, hairs. These root hairs absorb water and, minerals from the soil., , 5.1.2, , Figure 5.3 The regions of the root-tip, , Modifications of Root, , Roots in some plants change their shape and, structure and become modified to perform, functions other than absorption and, conduction of water and minerals. They are, modified for support, storage of food and, respiration (Figure 5.4 and 5.5). Tap roots of, carrot, turnip and adventitious roots of sweet, potato, get swollen and store food. Can you give, some more such examples? Have you ever, wondered what those hanging structures that, support a banyan tree are? These are called, prop roots. Similarly, the stems of maize and, sugarcane have supporting roots coming out, of the lower nodes of the stem. These are called, stilt roots. In some plants such as Rhizophora, growing in swampy areas, many roots come out, of the ground and grow vertically upwards., Such roots, called pneumatophores, help to, get oxygen for respiration (Figure 5.5b)., , Figure 5.4, , 2021-22, , Modification of root for support:, Banyan tree
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68, , BIOLOGY, , Turnip, Asparagus, , Figure 5.5, , Carrot, , Sweet, potato, , (b), , (a), , Modification of root for : (a) storage (b) respiration: pneumatophore in, Rhizophora, , 5.2 THE STEM, What are the features that distinguish a stem from a root? The stem is the, ascending part of the axis bearing branches, leaves, flowers and fruits. It, develops from the plumule of the embryo of a germinating seed. The stem, bears nodes and internodes. The region of the stem where leaves are, born are called nodes while internodes are the portions between two nodes., The stem bears buds, which may be terminal or axillary. Stem is generally, green when young and later often become woody and dark brown., The main function of the stem is spreading out branches bearing, leaves, flowers and fruits. It conducts water, minerals and photosynthates., Some stems perform the function of storage of food, support, protection, and of vegetative propagation., , 5.2.1, , Modifications of Stem, , The stem may not always be typically like what they are expected to be., They are modified to perform different functions (Figure 5.6). Underground, stems of potato, ginger, turmeric, zaminkand, Colocasia are modified to, store food in them. They also act as organs of perennation to tide over, conditions unfavourable for growth. Stem tendrils which develop from, axillary buds, are slender and spirally coiled and help plants to climb, such as in gourds (cucumber, pumpkins, watermelon) and grapevines., Axillary buds of stems may also get modified into woody, straight and, pointed thorns. Thorns are found in many plants such as Citrus,, Bougainvillea. They protect plants from browsing animals. Some plants, of arid regions modify their stems into flattened (Opuntia), or fleshy, cylindrical (Euphorbia) structures. They contain chlorophyll and carry, , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 69, , Axillary bud, modified, into tendril, , Ginger, Potato, , Zaminkand, , (b), , (a), , Stem modified, into spine, Bougainvillea sp., , Oxalis sp., , (c), , Figure 5.6, , (d), , Roots arising, from nodes, , Modifications of stem for : (a) storage (b) support (c) protection, (d) spread and vegetative propagation, , out photosynthesis. Underground stems of some plants such as grass, and strawberry, etc., spread to new niches and when older parts die new, plants are formed. In plants like mint and jasmine a slender lateral branch, arises from the base of the main axis and after growing aerially for some, time arch downwards to touch the ground. A lateral branch with short, internodes and each node bearing a rosette of leaves and a tuft of roots is, found in aquatic plants like Pistia and Eichhornia. In banana, pineapple, and Chrysanthemum, the lateral branches originate from the basal and, underground portion of the main stem, grow horizontally beneath the, soil and then come out obliquely upward giving rise to leafy shoots., , 5.3 THE LEAF, The leaf is a lateral, generally flattened structure borne on the stem. It, develops at the node and bears a bud in its axil. The axillary bud later, develops into a branch. Leaves originate from shoot apical meristems and, are arranged in an acropetal order. They are the most important vegetative, organs for photosynthesis., A typical leaf consists of three main parts: leaf base, petiole and lamina, (Figure 5.7 a). The leaf is attached to the stem by the leaf base and may, , 2021-22
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70, , BIOLOGY, , Lamina, Stipule, , Petiole, , (a), , Leaf, base, , Axillary, bud, , bear two lateral small leaf like structures called, stipules. In monocotyledons, the leaf base expands, into a sheath covering the stem partially or wholly., In some leguminous plants the leafbase may, become swollen, which is called the pulvinus. The, petiole help hold the blade to light. Long thin flexible, petioles allow leaf blades to flutter in wind, thereby, cooling the leaf and bringing fresh air to leaf surface., The lamina or the leaf blade is the green expanded, part of the leaf with veins and veinlets. There is,, usually, a middle prominent vein, which is known, as the midrib. Veins provide rigidity to the leaf blade, and act as channels of transport for water, minerals, and food materials. The shape, margin, apex, surface, and extent of incision of lamina varies in different, leaves., , 5.3.1, , (b), Figure 5.7, , (c), Structure of a leaf :, (a) Parts of a leaf, (b) Reticulate venation, (c) Parallel venation, , Rachis, , (b) Silk Cotton, (a) Neem, Figure 5.8, , Compound leaves :, (a) pinnately compound leaf, (b) palmately compound leaf, , Venation, , The arrangement of veins and the veinlets in the, lamina of leaf is termed as venation. When the, veinlets form a network, the venation is termed as, reticulate (Figure 5.7 b). When the veins run, parallel to each other within a lamina, the venation, is termed as parallel (Figure 5.7 c). Leaves of, dicotyledonous plants generally possess reticulate, venation, while parallel venation is the characteristic, of most monocotyledons., , 5.3.2, , Types of Leaves, , A leaf is said to be simple, when its lamina is entire, or when incised, the incisions do not touch the, midrib. When the incisions of the lamina reach up, to the midrib breaking it into a number of leaflets,, the leaf is called compound. A bud is present, in the axil of petiole in both simple and compound, leaves, but not in the axil of leaflets of the compound, leaf., The compound leaves may be of two types, (Figure 5.8). In a pinnately compound leaf a, number of leaflets are present on a common axis,, the rachis, which represents the midrib of the leaf, as in neem., , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 71, , In palmately compound leaves, the, leaflets are attached at a common point, i.e.,, at the tip of petiole, as in silk cotton., , 5.3.3, , Phyllotaxy, , Phyllotaxy is the pattern of arrangement of, leaves on the stem or branch. This is usually, of three types – alternate, opposite and, whorled (Figure 5.9). In alternate type of, phyllotaxy, a single leaf arises at each node, in alternate manner, as in china rose,, mustard and sun flower plants. In opposite, type, a pair of leaves arise at each node and, lie opposite to each other as in Calotropis, and guava plants. If more than two leaves, arise at a node and form a whorl, it is called, whorled, as in Alstonia., , 5.3.4 Modifications of Leaves, , (b) Guava, (a) China rose, , (c) Alstonia, Figure 5.9 Different types of phyllotaxy :, (a) Alternate (b) Opposite, (c) Whorled, , Leaves are often modified to perform, functions other than photosynthesis. They, are converted into tendrils for climbing as, in peas or into spines for defence as in cacti, (Figure 5.10 a, b). The fleshy leaves of onion, and garlic store food (Figure 5.10c). In some, plants such as Australian acacia, the leaves, are small and short-lived. The petioles in, these plants expand, become green and, synthesise food. Leaves of certain, insectivorous plants such as pitcher plant,, venus-fly trap are also modified leaves., , Leaves, modified, into spines, , Leaf, tendril, , (b) Cactus, (a) Pea, , 5.4 THE INFLORESCENCE, A flower is a modified shoot wherein the shoot, apical meristem changes to floral meristem., Internodes do not elongate and the axis gets, condensed. The apex produces different, kinds of floral appendages laterally at, successive nodes instead of leaves. When a, shoot tip transforms into a flower, it is always, solitary. The arrangement of flowers on the, , Fleshy, leaves, , (c) Onion, , Figure 5.10 Modifications of leaf for :, (a) support: tendril (b) protection:, spines (c) storage: fleshy leaves, , 2021-22
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72, , BIOLOGY, , floral axis is termed as inflorescence. Depending, on whether the apex gets developed into a flower or, continues to grow, two major types of inflorescences, are defined – racemose and cymose. In racemose, type of inflorescences the main axis continues to, grow, the flowers are borne laterally in an acropetal, succession (Figure 5.11)., In cymose type of inflorescence the main axis, terminates in a flower, hence is limited in growth.The, flowers are borne in a basipetal order (Figure 5.12)., , 5.5 THE FLOWER, , Figure 5.11, , Racemose inflorescence, , Figure 5.12 Cymose inflorescence, , The flower is the reproductive unit in the, angiosperms. It is meant for sexual reproduction., A typical flower has four different kinds of whorls, arranged successively on the swollen end of the, stalk or pedicel, called thalamus or receptacle., These are calyx, corolla, androecium and, gynoecium. Calyx and corolla are accessory organs,, while androecium and gynoecium are reproductive, organs. In some flowers like lily, the calyx and, corolla are not distinct and are termed as perianth., When a flower has both androecium and, gynoecium, it is bisexual. A flower having either, only stamens or only carpels is unisexual., In symmetry, the flower may be, actinomorphic (radial symmetry) or, zygomorphic (bilateral symmetry). When a flower, can be divided into two equal radial halves in any, radial plane passing through the centre, it is said, to be actinomorphic, e.g., mustard, datura, chilli., When it can be divided into two similar halves only, in one particular vertical plane, it is zygomorphic,, e.g., pea, gulmohur, bean, Cassia. A flower is, asymmetric (irregular) if it cannot be divided into, two similar halves by any vertical plane passing, through the centre, as in canna., A flower may be trimerous, tetramerous or, pentamerous when the floral appendages are in, multiple of 3, 4 or 5, respectively. Flowers, with bracts -reduced leaf found at the base of the, pedicel - are called bracteate and those without, bracts, ebracteate., , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , (a), , 73, , (b), , (c), , (d), , Figure 5.13 Position of floral parts on thalamus : (a) Hypogynous (b), Perigynous (d) Epigynous, , Based on the position of calyx, corolla and androecium in respect of, the ovary on thalamus, the flowers are described as hypogynous,, perigynous and epigynous (Figure 5.13). In the hypogynous flower the, gynoecium occupies the highest position while the other parts are situated, below it. The ovary in such flowers is said to be superior, e.g., mustard,, china rose and brinjal. If gynoecium is situated in the centre and other, parts of the flower are located on the rim of the thalamus almost at the, same level, it is called perigynous. The ovary here is said to be half, inferior, e.g., plum, rose, peach. In epigynous flowers, the margin of, thalamus grows upward enclosing the ovary completely and getting fused, with it, the other parts of flower arise above the ovary. Hence, the ovary is, said to be inferior as in flowers of guava and cucumber, and the ray, florets of sunflower., , 5.5.1, , Parts of a Flower, , Each flower normally has four floral whorls, viz., calyx, corolla,, androecium and gynoecium (Figure 5.14)., 5.5.1.1, , Calyx, , The calyx is the outermost whorl of the flower and the members are called, sepals. Generally, sepals are green, leaf like and protect the flower in the, bud stage. The calyx may be gamosepalous (sepals united) or, polysepalous (sepals free)., 5.5.1.2, , Corolla, , Corolla is composed of petals. Petals are usually brightly coloured to, attract insects for pollination. Like calyx, corolla may also be, , 2021-22, , and (c)
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74, , BIOLOGY, , Androecium, Gynoecium, Corolla, Calyx, Pedicel, , Figure 5.14 Parts of a flower, , gamopetalous (petals united) or polypetalous (petals free). The shape, and colour of corolla vary greatly in plants. Corolla may be tubular, bellshaped, funnel-shaped or wheel-shaped., Aestivation: The mode of arrangement of sepals or petals in floral bud, with respect to the other members of the same whorl is known as, aestivation. The main types of aestivation are valvate, twisted, imbricate, and vexillary (Figure 5.15). When sepals or petals in a whorl just touch, one another at the margin, without overlapping, as in Calotropis, it is, said to be valvate. If one margin of the appendage overlaps that of the, next one and so on as in china rose, lady’s finger and cotton, it is called, twisted. If the margins of sepals or petals overlap one another but not in, any particular direction as in Cassia and gulmohur, the aestivation is, called imbricate. In pea and bean flowers, there are five petals, the largest, (standard) overlaps the two lateral petals (wings) which in turn overlap, the two smallest anterior petals (keel); this type of aestivation is known, as vexillary or papilionaceous., , (a), , (b), , (c), , (d), , Figure 5.15 Types of aestivation in corolla : (a) Valvate (b) Twisted (c) Imbricate (d) Vexillary, , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 75, (, , )a, , 5.5.1.3, , Androecium, , Androecium is composed of stamens. Each stamen which, represents the male reproductive organ consists of a stalk or a, filament and an anther. Each anther is usually bilobed and each, lobe has two chambers, the pollen-sacs. The pollen grains are, produced in pollen-sacs. A sterile stamen is called staminode., Stamens of flower may be united with other members such as, petals or among themselves. When stamens are attached to the, petals, they are epipetalous as in brinjal, or epiphyllous when, attached to the perianth as in the flowers of lily. The stamens in a, flower may either remain free (polyandrous) or may be united in, varying degrees. The stamens may be united into one bunch or, one bundle (monoadelphous) as in china rose, or two bundles, (diadelphous) as in pea, or into more than two bundles, (polyadelphous) as in citrus. There may be a variation in the length, of filaments within a flower, as in Salvia and mustard., 5.5.1.4, , (a), , (b), , Gynoecium, , Gynoecium is the female reproductive part of the flower and is made, up of one or more carpels. A carpel consists of three parts namely, stigma, style and ovary. Ovary is the enlarged basal part, on which, lies the elongated tube, the style. The style connects the ovary to the, stigma. The stigma is usually at the tip of the style and is the, receptive surface for pollen grains. Each ovary bears one or more, ovules attached to a flattened, cushion-like placenta. When more, than one carpel is present, they may be free (as in lotus and rose), and are called apocarpous. They are termed syncarpous when, carpels are fused, as in mustard and tomato. After fertilisation, the, ovules develop into seeds and the ovary matures into a fruit., , (c), , (d), , Placentation: The arrangement of ovules within the ovary is known, as placentation. The placentation are of different types namely,, marginal, axile, parietal, basal, central and free central (Figure 5.16)., In marginal placentation the placenta forms a ridge along the, ventral suture of the ovary and the ovules are borne on this ridge, forming two rows, as in pea. When the placenta is axial and the, (e), ovules are attached to it in a multilocular ovary, the placentaion is, said to be axile, as in china rose, tomato and lemon. In parietal, Figure 5.16 Types of, placentation, the ovules develop on the inner wall of the ovary or, placentation :, (a) Marginal, on peripheral part. Ovary is one-chambered but it becomes two(b) Axile, chambered due to the formation of the false septum, e.g., mustard, (c) Parietal, and Argemone. When the ovules are borne on central axis and, (d) Free central, (e) Basal, septa are absent, as in Dianthus and Primrose the placentation is, , 2021-22
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76, , BIOLOGY, , called free central. In basal placentation, the placenta develops at the, base of ovary and a single ovule is attached to it, as in sunflower, marigold., , 5.6 THE FRUIT, The fruit is a characteristic feature of the flowering plants. It is a mature, or ripened ovary, developed after fertilisation. If a fruit is formed without, fertilisation of the ovary, it is called a parthenocarpic fruit., Generally, the fruit consists of a wall or pericarp and seeds. The, pericarp may be dry or fleshy. When pericarp is thick and fleshy, it is, differentiated into the outer epicarp, the middle mesocarp and the inner, endocarp., , (a), , (b), , Figure 5.17 Parts of a fruit : (a) Mango (b) Coconut, , In mango and coconut, the fruit is known as a drupe (Figure 5.17)., They develop from monocarpellary superior ovaries and are one seeded., In mango the pericarp is well differentiated into an outer thin epicarp, a, middle fleshy edible mesocarp and an inner stony hard endocarp. In, coconut which is also a drupe, the mesocarp is fibrous., , 5.7 THE SEED, The ovules after fertilisation, develop into seeds. A seed is made up of a, seed coat and an embryo. The embryo is made up of a radicle, an embryonal, axis and one (as in wheat, maize) or two cotyledons (as in gram and pea)., , 5.7.1, , Structure of a Dicotyledonous Seed, , The outermost covering of a seed is the seed coat. The seed coat has two, layers, the outer testa and the inner tegmen. The hilum is a scar on the, seed coat through which the developing seeds were attached to the fruit., Above the hilum is a small pore called the micropyle. Within the seed, , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , coat is the embryo, consisting of an, embryonal axis and two cotyledons. The, cotyledons are often fleshy and full of reserve, food materials. At the two ends of the, embryonal axis are present the radicle and, the plumule (Figure 5.18). In some seeds, such as castor the endosperm formed as a, result of double fertilisation, is a food storing, tissue and called endospermic seeds. In, plants such as bean, gram and pea, the, endosperm is not present in mature seeds, and such seeds are called nonendospermous., , 5.7.2, , 77, Seed coat, , Cotyledon, Plumule, , Hilum, Radicle, Micropyle, Figure 5.18 Structure of dicotyledonous seed, , Structure of Monocotyledonous Seed, , Generally, monocotyledonous seeds are endospermic but some as in, orchids are non-endospermic. In the seeds of cereals such as maize the, seed coat is membranous and generally fused with the fruit wall. The, endosperm is bulky and stores food. The outer covering of endosperm, separates the embryo by a proteinous layer called aleurone layer. The, embryo is small and situated in a groove at one end of the endosperm. It, consists of one large and shield shaped cotyledon known as scutellum, and a short axis with a plumule and a radicle. The plumule and radicle, are enclosed in sheaths which are called coleoptile and coleorhiza, respectively (Figure 5.19)., , Seed coat & fruit-wall, , Endosperm, , Aleurone layer, Scutellum, Coleoptile, Endosperm, , Plumule, , Embryo, , Radicle, Coleorhiza, , Figure 5.19 Structure of a monocotyledonous seed, , 2021-22
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78, , BIOLOGY, , 5.8 SEMI-TECHNICAL DESCRIPTION, FLOWERING PLANT, , ⊕, , K2+2 C4 A2+4 G(2), , Figure 5.20 Floral diagram with, floral formula, , OF A, , TYPICAL, , Various morphological features are used to describe a, flowering plant. The description has to be brief, in a simple, and scientific language and presented in a proper, sequence. The plant is described beginning with its habit,, vegetative characters – roots, stem and leaves and then, floral characters inflorescence and flower parts. After, describing various parts of plant, a floral diagram and a, floral formula are presented. The floral formula is, represented by some symbols. In the floral formula, Br, stands for bracteate K stands for calyx , C for corolla, P for, perianth, A for androecium and G for Gynoecium, G for, superior ovary and G for inferior ovary,, for male, for, female,, for bisexual plants, ⊕ for actinomorphic and, for zygomorphic nature of flower. Fusion is indicated by, enclosing the figure within bracket and adhesion by a line, drawn above the symbols of the floral parts. A floral, diagram provides information about the number of parts, of a flower, their arrangement and the relation they have, with one another (Figure 5.20). The position of the mother, axis with respect to the flower is represented by a dot on, the top of the floral diagram. Calyx, corolla, androecium, and gynoecium are drawn in successive whorls, calyx being, the outermost and the gynoecium being in the centre., Floral formula also shows cohesion and adhesion within, parts of whorls and between whorls. The floral diagram, and floral formula in Figure 5.20 represents the mustard, plant (Family: Brassicaceae)., , 5.9, , DESCRIPTION, , 5.9.1, , OF, , SOME IMPORTANT FAMILIES, , Fabaceae, , This family was earlier called Papilionoideae, a subfamily, of family Leguminosae. It is distributed all over the world, (Figure 5.21)., Vegetative Characters, Trees, shrubs, herbs; root with root nodules, Stem: erect or climber, Leaves: alternate, pinnately compound or simple; leaf base,, pulvinate; stipulate; venation reticulate., , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 79, , (b), (c), , (e), (d), , (a), , (f), , Figure 5.21 Pisum sativum (pea) plant : (a) Flowering twig (b) Flower (c) Petals, (d) Reproductive parts (e) L.S.carpel (f) Floral diagram, , Floral characters, Inflorescence: racemose, Flower: bisexual, zygomorphic, Calyx: sepals five, gamosepalous; valvate/imbricate aestivation, Corolla: petals five, polypetalous, papilionaceous, consisting of a posterior, standard, two lateral wings, two anterior ones forming a keel (enclosing, stamens and pistil), vexillary aestivation, Androecium: ten, diadelphous, anther dithecous, Gynoecium: ovary superior, mono carpellary, unilocular with many, ovules, style single, Fruit: legume; seed: one to many, non-endospermic, Floral Formula: %, , K(5) C1+2+(2) A(9)+1 G1, , Economic importance, Many plants belonging to the family are sources of pulses (gram, arhar,, sem, moong, soyabean; edible oil (soyabean, groundnut); dye (Indigofera);, fibres (sunhemp); fodder (Sesbania, Trifolium), ornamentals (lupin, sweet, pea); medicine (muliathi)., , 5.9.2, , Solanaceae, , It is a large family, commonly called as the ‘potato family’. It is widely, distributed in tropics, subtropics and even temperate zones (Figure 5.22)., Vegetative Characters, Plants mostly herbs, shrubs and rarely small trees, Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid, , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 81, , 5.9.3 Liliaceae, Commonly called the ‘Lily family’ is a characteristic representative of, monocotyledonous plants. It is distributed world wide (Figure 5.23)., Vegetative characters: Perennial herbs with underground bulbs/corms/, rhizomes, Leaves mostly basal, alternate, linear, exstipulate with parallel venation, Floral characters, Inflorescence: solitary / cymose; often umbellate clusters, Flower: bisexual; actinomorphic, Perianth tepal six (3+3), often united into tube; valvate aestivation, Androecium: stamen six, 3+3, epitepalous, Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with, many ovules; axile placentation, Fruit: capsule, rarely berry, Seed: endospermous, Floral Formula: Br ⊕ P(3+3) A3+3 G(3), Economic Importance, Many plants belonging to this family are good ornamentals (tulip,, Gloriosa), source of medicine (Aloe), vegetables (Asparagus), and, colchicine (Colchicum autumnale)., , (b), , (c), (d), , (a), Figure 5.23 Allium cepa (onion) plant : (a) Plant (b) Inflorescence (c) Flower, (d) Floral diagram, , 2021-22
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82, , BIOLOGY, , SUMMARY, Flowering plants exhibit enormous variation in shape, size, structure, mode of, nutrition, life span, habit and habitat. They have well developed root and shoot, systems. Root system is either tap root or fibrous. Generally, dicotyledonous plants, have tap roots while monocotyledonous plants have fibrous roots. The roots in, some plants get modified for storage of food, mechanical support and respiration., The shoot system is differentiated into stem, leaves, flowers and fruits. The, morphological features of stems like the presence of nodes and internodes,, multicellular hair and positively phototropic nature help to differentiate the stems, from roots. Stems also get modified to perform diverse functions such as storage, of food, vegetative propagation and protection under different conditions. Leaf is a, lateral outgrowth of stem developed exogeneously at the node. These are green in, colour to perform the function of photosynthesis. Leaves exhibit marked variations, in their shape, size, margin, apex and extent of incisions of leaf blade (lamina)., Like other parts of plants, the leaves also get modified into other structures such, as tendrils, spines for climbing and protection respectively., The flower is a modified shoot, meant for sexual reproduction. The flowers are, arranged in different types of inflorescences. They exhibit enormous variation in, structure, symmetry, position of ovary in relation to other parts, arrangement of, petals, sepals, ovules etc. After fertilisation, the ovary is modified into fruits and, ovules into seeds. Seeds either may be monocotyledonous or dicotyledonous. They, vary in shape, size and period of viability. The floral characteristics form the basis, of classification and identification of flowering plants. This can be illustrated, through semi-technical descriptions of families. Hence, a flowering plant is, described in a definite sequence by using scientific terms. The floral features are, represented in the summarised form as floral diagrams and floral formula., , EXERCISES, 1. What is meant by modification of root? What type of modification of root is found, in the:, (a) Banyan tree (b) Turnip (c) Mangrove trees, 2. Justify the following statements on the basis of external features:, (i) Underground parts of a plant are not always roots., (ii) Flower is a modified shoot., 3. How is a pinnately compound leaf different from a palmately compound leaf?, 4. Explain with suitable examples the different types of phyllotaxy., , 2021-22
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MORPHOLOGY OF FLOWERING PLANTS, , 83, , 5. Define the following terms:, (a) aestivation, (d) zygomorphic, (g) epipetalous stamen, , (b) placentation, (e) superior ovary, , (c) actinomorphic, (f) perigynous flower, , 6. Differentiate between, (a) Racemose and cymose inflorescence, (b) Fibrous root and adventitious root, (c) Apocarpous and syncarpous ovary, 7. Draw the labelled diagram of the following:, (i) gram seed (ii) V.S. of maize seed, 8. Describe modifications of stem with suitable examples., 9. Take one flower each of the families Fabaceae and Solanaceae and write its, semi-technical description. Also draw their floral diagram after studying them., 10. Describe the various types of placentations found in flowering plants., 11. What is a flower? Describe the parts of a typical angiosperm flower., 12. How do the various leaf modifications help plants?, 13. Define the term inflorescence. Explain the basis for the different types, inflorescence in flowering plants., 14. Write the floral formula of a actinomorphic, bisexual, hypogynous flower with, five united sepals, five free petals, five free stamens and two united carples, with superior ovary and axile placentation., 15. Describe the arrangement of floral members in relation to their insertion on, thalamus., , 2021-22
