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Morphology Of Flowering Plants The angiosperms are all characterised by presence of roots, stems, leaves, flowers and fruits. 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. The Root In majority of the dicotyledonous plants (The dicotyledons, also known as dicots (or more rarely dicotyls), were one of the two groups into which all the flowering plants or angiosperms were formerly divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons), 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 roots. The primary roots and its branches constitute the tap root system, as seen in the mustard plant . In monocotyledonous plants (monocots), 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 .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 . 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. Regions of the Root The root is covered at the apex (the growing point of a shoot) by a thimble (cap)-like structure called the root cap . 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 (A meristem is the tissue in most plants containing undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place. Meristematic cells give rise to various organs of the plant and keep the plant growing)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. 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 .Tap roots of carrot, turnips and adventitious roots of sweet potato, get swollen and store food. Banyan tree roots 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, roots come out of the ground and grow vertically upwards. Such roots, called pneumatophores, help to get oxygen for respiration. Rhizophora THE STEM 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 (terminal, when located at the tip of a stem (apical is equivalent but rather reserved for the one at the top of the plant);axillary, when located in the axil of a leaf (lateral is the equivalent but some adventitious buds may be lateral too); ). 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. Plumule After an ovule undergoes fertilization, a seed develops, growing a protective layer known as the testa around the developing embryo. This embryo contains the three parts listed above. Within a short time after fertilization, the plumule becomes visible with at least two leaves that have a growing point held between them. While the formation of a solid root system is important, the development of the plumule is also instrumental in the plant's eventual thriving or failure. If the plumule develops in a normal way, the shoot emerges from the seed and works its way up through the soil and into the atmosphere. A healthy plumule develops cotyledons, a special type of leaf that holds seeds; this is one of the most important ways that these plants germinate. Because these seeds are crucial to the spread of that particular species, a plumule that fails to thrive not only threatens the health of that particular plant but the very existence of dozens, if not hundreds, more down the line. Modifications of Stem The stem may not always be typically like what they are expected to be. They are modified to perform different functions . Underground stems of potato, ginger, turmeric, zaminkand, Colocasia are modified to store food in them. They also act as organs of perenation 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 out photosynthesis. Underground stems of some plants such as grass and strawberry, etc., spread to new niches (a shallow recess, especially one in a wall to display a statue or other ornament) 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 (occurring in the air)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 (forming or belonging to a bottom layer or base)and underground portion of the main stem, grow horizontally beneath the soil and then come out obliquely (not in direct way) upward giving rise to leafy shoots. Modifications of stem for : (a) storage (b) support (c) protection (d) spread and vegetative propagation 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 . The leaf is attached to the stem by the leaf base and may 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 (cut) of lamina varies in different leaves. 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 .When the veins run parallel to each other within a lamina, the venation is termed as parallel .Leaves of dicotyledonous plants generally possess reticulate venation, while parallel venation is the characteristic of most monocotyledons. 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 : 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. In palmately compound leaves, the leaflets are attached at a common point, i.e., at the tip of petiole, as in silk cotton. Phyllotaxy Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. This is usually of three types – alternate, opposite and whorled . 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. China Rose Calotropis Alstonia Modifications of Leaves 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 . The fleshy leaves of onion and garlic store food .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. THE INFLORESCENCE A flower is a modified shoot where in 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. Depending on whether the apex gets converted 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 (developing or opening in succession from base to apex). In cymose type of inflorescence the main axis terminates in a flower, hence is limited in growth.The flowers are borne in a basipetal (produced in order from the apex downwards so that the youngest are at the base)order . In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts. They do not have a lamina or blade, but they can photosynthesize. THE FLOWER 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 (the female reproductive organ of a flower, consisting of an ovary, a stigma, and usually a style. It may occur singly or as one of a group) 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 (cinnamon). 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. 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 . In the hypogynous flower the gynoecium (the female part of a flower, consisting of one or more carpels)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. Thalamus: Insertion of Floral Leaves on Thalamus In the below mentioned article, we will discuss about the insertion of floral leaves on thalamus. Thalamus (also called torus) is the axis of the floral shoot which is the direct pro-longation of the pedicel and bears four sets of floral members. Usually, it is a slightly swollen knob-like structure but sometimes it may be somewhat elongated and conical bearing floral leaves spirally as in Artabotrys , Michelia , etc., or like an inverted cone with a spongy flat top as in lotus , or it may be slightly convex as in brinjal, etc. In perigynous and epigynous flowers the thalamus becomes flat or cup-shaped as explained under leaf insertion. The thalamus of most flowers has three internodes which are very much condensed. But, in certain flowers these internodes are elongated. The first inter-node (between calyx and corolla) is called the anthophore (anthos=flower), the second internode (between corolla and androecium) is the androphore (also called gynandrophore) and the third internode (between androecium and gynoecium) is called the gynophore. Cleome gynandra shows both androphore and gynophore (gynandrophore). Capparis sepiaria and Pterospermum acerifolium show gynophores only. Passionflower (Passiflora suberosa of Passifloraceae) shows an androphore . The thalamus is terminated by the pistil except in cases of monstrous development. But, in the family Umbelliferae the thalamus normally projects into the ovary and the carpels remain attached to it separating at maturity. This prolongation of the thalamus is called the carpophore. This is seen in the fruits of anise, Foeniculum, Coriandrum, etc. Any portion of the thalamus may be modified in certain flowers into characteristic structures called discs. The discs often bear nectar glands. Thus, the family Rutaceae (orange, lemon, etc.) has fleshy annular discs surrounding the bases of the pistils . In grape vine (Vitis sp. of Vitaceae) the disc is formed of some scaly structures . The disc may be hypogynous, perigynous or epigynous according as it is below, around or on the top of the ovary. Insertion of Floral Leaves on the Thalamus: In a typical flower the thalamus is a slightly swollen (conical, convex, etc.) struc-ture with the calyx, corolla, androecium and gynoecium developed successively on it. It is terminated by the pistil so that the gynoecium is on the top . Such a flower is hypogynous (i.e., other members below gynoecium). The ovary here is superior and other members inferior. This condition may be seen in many common flowers like magnolia, mustard, brinjal, etc. If the thalamus be flattened out to form a flat or a cup-shaped concave top, the gynoecium will be placed not on the top of the flower but at the centre. The other three whorls are usually inserted on the rim of the flat or the concave halamus. Such an ovary may also be partially sunken in the thalamus. This is called the perigynous condition as the other members surround the gynoecium. Examples of the first (i.e., thalamus more or less flat) type may be found in the peas, strawberry, etc., while the second type (thalamus forming a concave receptacle) is found in rose, etc. Here also the gynoecium is usually described as superior although it is not actually on the top of the flower. Sometimes, the term half-inferior is used instead of superior. In a third type the cup-shaped thalamus as seen may fuse with the wall of the ovary giving the appearance as in . It now appears that the gynoecium is the lowest or the inferior whorl of the flower while all other members are superior, i.e., the condition is epigynous. Epigyny may be seen in the unisexual female flowers of cucurbits and in plants like banana, guava, sunflower, etc. It should be noted that in an epigynous flower the wall of the ovary has also got the thalamus fused with it. Thus, any fruit developed out of this ovary has this thalamus tissue on the outside. This statement is further strengthened by the fact that in some gooseberry one or two foliage leaves are sometimes seen to develop on the fruit wall. This is possible because of the stem nature of the thalamus. Flower Anotomy Lily Datura: Jimson weed or Devil's snare Plum Peach is used for extracting cinnamon Cassia or Cinnamon , bark Parts of a Flower 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). Corolla Corolla is composed of petals. Petals are usually brightly coloured to attract insects for pollination. Like calyx, corolla may be also free (gamopetalous) or united (polypetalous). The shape and colour of corolla vary greatly in plants. Corolla may be tubular, bell-shaped, 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. 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. Calotropis Pea Flower 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 (the outer part of a flower, consisting of the calyx (sepals) and corolla (petals))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. 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. 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 . 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 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 placentation, the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two- chambered due to the formation of the false septum (a partition separating two chambers, such as that between the nostrils or the chambers of the heart), e.g., mustard and Argemone. When the ovules are borne on central axis and septa are absent, as in Dianthus and Primrose the placentation is 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. Brinjal Flower Lily Flower Citrus Salvia Lemon Placentation Tomato Placentation Marigold Placentation 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. In mango and coconut, the fruit is known as a drupe. They develop from monocarpellary (consisting of a single carpe) 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. 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 (The embryo, or immature plant, is divided into regions by an embryonic axis region that eventually becomes the stem) and one (as in wheat, maize) or two cotyledons (as in gram or chana and pea). 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 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. In some seeds such as castor the endosperm formed as a result of double fertilisation, is a food storing tissue. In plants such as bean, gram and pea, the endosperm is not present in mature seeds and such seeds are called nonendospermous. 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. Orchid Maize or Corn Wheat Gram or Chana Castor use for extracting oil MORE ABOUT MONOCOTS AND DICOTS Monocots and Dicots Chart showing Differences Monocot Dicot SEED Monocots have only one seed leaf inside the seed coat. It is often only a thin leaf, because the endosperm to feed the new plant is not inside the seed leaf. Dicots have two seed leaves inside the seed coat. They are usually rounded and fat, because they contain the endosperm to feed the embryo plant. GERMINATION Homeria Lilium Gloriosa When a monocot seed germinates, it produces a single leaf. It is usually long and narrow, like the adult leaf. Even when it is quite a round shape, there is only one seed leaf in a monocot. Eryngium Sanguisorba Cladanthus When a dicot germinates, it produces two seedleaves. They contain the food for the new plant, so they are usually fatter than the true leaves. The first true leaves are often a different shape. LEAVES Washingtonia Clivia Canna The leaves of monocots are often long and narrow, with their veins in straight lines up and down the leaf. Sometimes, the veins run from the centre of the leaf to the edge, parallel to one another. Malva Rosa Campanula Leaves of dicots come in many different shapes and sizes. The veins go from the central midrib to the edge of the leaf, crossing and joining to form a netted pattern all over the leaf. STEM & ROOTS Stem Sheath Root The stems of monocots are usually unbranched and fleshy. They do not grow thicker from year to year. New leaves often grow wrapped in a protective sheath formed by the older leaf. The roots of dicots are usually short and stringy. Dicots often have bulbs. Stem Stipule Root The stems of dicots are usually tough. They can grow wider each year and are often branched. They sometimes have stipules at the base of the leaf. The root is often a single long tap root with smaller roots growing from it. FLOWER Cyrtanthus Pleione Agapanthus The parts of the flower of monocots are in threes. The sepals are often the same colour as the petals, making it look as if the flower has six petals. There are usually the same number of stamens as petals. Oenothera Epilobium Geranium The flowers of dicots usually have flower parts in fours or fives. The calyx is a separate ring of sepals under the corolla, and is usually green. SEEDPOD Iris Anthericum Hedychium The seed pods or fruits of monocots usually have three parts. The seeds are often large and fleshy. The largest seed in the world, the Coco-de-Mer, and the smallest seeds in the world, Orchid seeds, are both monocot seeds. Lychnis Erigeron Clitoria The seedpods or fruits and the seeds of dicots are very variable in shape, size and texture. The seedpod can have any number of chambers, from none to many. There are often more seeds in a seedpod than in a monocot seedpod. SEMI-TECHNICAL DESCRIPTION OF A TYPICAL FLOWERING PLANT 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 . 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 in between whorls. The floral diagram and floral formula in represents the mustard plant (Family: Brassicaceae) Floral formula is a means to represent the structure of a flower using numbers, letters and various symbols, presenting substantial information about the flower in a compact form. It can represent particular species, or can be generalized to characterize higher taxa, usually giving ranges of organ numbers. Floral formulae are one of the two ways of describing flower structure developed during the 19th century, the other being floral diagrams.[2] The format of floral formulae differs between authors, yet they tend to convey the same information. Meaning of Floral Formula: It is a symbolic and numerical representation of various floral parts. It also furnishes information regarding symmetry, sexuality and interrelationship of various floral parts viz., calyx, corolla, androecium and gynoecium. Numerology of Symbols: A number put just after the symbol represents the number of parts in that particular whorl. If the parts of a whorl are united then the number is bracketed e.g. If five free sepals are present the whorl is represented by K5 and if united it is represented by K(5). If there are more than one whorl of an organ, they are represented by the some of their representative parts. If a flower has three whorls of five stamens each, then the androecium is represented by A5+5+5. If one organ is united with other organ then an arrow is made. It starts from the top of one symbol and ends on the top of the symbol for the other organ with which united e.g., if each of the five petals bears the stamens the union of two organs is represented as below; The epigenous condition of a flower is represented by a line placed above the number of carpels. While its hypogenous condition is represented by under-lining the number of its carpels e.g. The epigenous flower with five carpels is written G5 and the same type of hypogenous flower with five carpels is written as G5. The missing organ is represented by putting a zero or 0 after its symbol. If the number of organs in a whorl is more than ten its symbol is followed by the mark of infinity or ∞. Symbols Used in Construction of Floral Formula: Symbols used in construction of floral formulae are as below: How to Write Floral Formula? The writing of floral formula one should start from bract and bracteole then symmetry and sex of flower, calyx, corolla, androecium and gynoecium. The number of parts of each organ is indicated in figures (1, …… 4, 5) after the relevant symbol (K, C, A, G). If the parts are free, the figure numeral is placed as such but if they are united, the numeral figure is placed inside bracket (see numerology of symbols). In bilabiate structure, the number of parts broken into two figures depending upon the number of parts in the upper and lower lip. Adnation of members of different whorls is shown by joining the top of their symbols by a curved line A break in the alternation of parts of any two successive floral cycles is indicated by inserting a vertical line between the symbols of the two floral cycles. The position of ovary whether, it is superior, half inferior or inferior is shown by placing a horizontal line below in front and above the symbol of gynoecium respectively. How to Read Floral Formula? The following examples illustrate the methods of reading and constructing the floral formulae: The formulae read as follows: Lathyrus: Flower zygomorphic, hermaphrodite, gamosepalous, calyx with five sepals; polypetalous, corolla with five petals; androecium with ten stamens, diadelphous; gynoecium superior of one carpel. Ipomoea: Flower actinomorphic, hermaphrodite; calyx polysepalous with five sepals; corolla gamopetalous with five petals; androecium with five free epipetalous stamens; gynoecium syncarpous with two superior carpels. The floral diagram is always drawn circular in outline. The different floral whorls are represented in concentric circles, the sepals on the outermost circle, then the petals, the stamens and carpels towards the inner side (Fig. 11.2 & 11.3). The first step to draw a floral diagram is to examine mature floral buds which are due to open shortly but have not yet opened. Pluck the floral bud from the mother axis only after you have noted down the anterior and posterior sides. Floral parts are drawn in a floral diagram as they would be seen in their transverse sections below the mother axis. Make the floral diagram in the following sequential stages: 1. A very small circle is drawn above the floral diagram. This circle represents the mother axis. In actinomorphic flowers, the mother axis circle may be denoted as but in zygomorphic flowers it is drawn as. If the flowers are terminal, the mother axis is not drawn. 2. In bracteate flowers, a section of bract is drawn below the floral diagram. In flowers without any bract, such a section is not drawn. 3. In bracteolate flowers, bracteoles are drawn in section on the left and right sides of the diagram. 4. Note the number of sepals, their arrangement in relation to the mother axis and their aestivation. Draw transverse sections of sepals between the mother axis and the bract, keeping all these points in view. In case of odd number of sepals, the odd sepal would be drawn either posterior or anterior to the flower, i.e., opposite the mother axis or opposite the bract, respectively. 5. The same procedure is repeated for petals as for sepals. However petals should be drawn alternate with the sepals. 6. If the flower is zygomorphic, petals are drawn of unequal sizes. Same may be the case with the sepals also in zygomorphic flowers. 7. If any sepal or petal is spurred, it is shown by drawing a loop at the back of that particular part in the floral diagram. 8. If parts of sepals or of petals are fused, draw lines to connect their edges together in the floral diagram. 9. In the epipetalous condition (i.e. when stamens are joined with petals), link the stamens and petals with small radial lines. 10. In case of bilabiate calyx or corolla, the two lips are joined by bulging lines. 11. Count the number of stamens, the number of whorls in which they are arranged, their cohesion and agnation to other floral parts, their position in relation to petals, their introse or extrose position, and draw them inside the petals in the floral diagram. Stamens are represented through transverse sections of the anthers. In the obdiplostemonous condition, the stamens of the outer whorl are drawn opposite to the petals. Introse stamens face towards the centre whereas the extrose towards the petals. Staminodes are represented either by an asterisk (*) or by a cross (x). 12. The gynoecium is represented by a transverse section of the ovary. Also draw the number of locules and the number of ovules in each loculus in the ovary. Type of placentation is also drawn. Actinomorphic: characterized by radial symmetry, such as a starfish or the flower of a daisy. Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirally arranged. Actinomorphic[edit] Further information: Merosity Wurmbea stricta, its tepals in actinomorphic arrangement Most flowers are actinomorphic ("star shaped", "radial"), meaning they can be divided into 3 or more identical sectors which are related to each other by rotation about the centre of the flower. Typically, each sector might contain one tepal or one petal and one sepal and so on. It may or may not be possible to divide the flower into symmetrical halves by the same number of longitudinal planes passing through the axis: Oleander is an example of a flower without such mirror planes. Actinomorphic flowers are also called radially symmetrical or regular flowers. Other examples of actinomorphic flowers are the lily (Lilium, Liliaceae) and the buttercup (Ranunculus, Ranunculaceae). Zygomorphic[edit] Satyrium carneum. Ground orchid with typical zygomorphic floral anatomy Zygomorphic ("yoke shaped", "bilateral" - from the Greek ζυγόν, zygon, yoke, and μορφή, morphe, shape) flowers can be divided by only a single plane into two mirror-image halves, much like a yoke or a person's face. Examples are orchids and the flowers of most members of the Lamiales (e.g., Scrophulariaceae and Gesneriaceae). Some authors prefer the term monosymmetry or bilateral symmetry.[1] Asymmetric[edit] A few plant species have flowers lacking any symmetry, and therefore having a "handedness". Examples are Valeriana officinalis and Canna indica.[2] Differences[edit] Actinomorphic flowers are a basal angiosperm character; zygomorphic flowers are a derived character that has evolved many times.[3] Some familiar and seemingly actinomorphic so-called flowers, such as those of daisies and dandelions (Asteraceae), and most species of Protea, are actually clusters of tiny (not necessarily actinomorphic) flowers arranged into a roughly radially symmetric inflorescence of the form known as a head, capitulum, or pseudanthium. Peloria[edit] Digitalis purpurea (common foxglove) displaying an aberrant peloric terminal flower and normal zygomorphic flowers Peloria or a peloric flower refers to an aberration in which a plant that normally produces zygomorphic flowers produces actinomorphic flowers instead. This aberration can be developmental, or it can have a genetic basis: the CYCLOIDEA gene controls floral symmetry. Peloric Antirrhinum plants have been produced by knocking out this gene.[3] Many modern cultivars of Sinningia speciosa ("gloxinia") have been bred to have peloric flowers as they are larger and showier than the normally zygomorphic flowers of this species. Charles Darwin explored peloria in Antirrhinum (snapdragon) while researching the inheritance of floral characteristics for his The Variation of Animals and Plants under Domestication.[4] Later research, using Digitalis purpurea, showed that his results[5] were largely in line with Mendelian theory.[6] Floral symmetry groups[edit] If we consider only those flowers which consist in a single flower, rather than a flower head or inflorescence, we can group the flowers into a relatively small number of 2D symmetry groups. Monocots are identifiable by their trimerous petals, thus monocots often have rotational symmetry of order 3. If the flower also has 3 lines of mirror symmetry the group it belongs to is the dihedral group D3. If not, then it belongs to the cyclic group C3. Eudicots with tetramerous or pentamerous petals may have rotational symmetry of order 4 or 5. Again, whether they also have mirror planes decides whether they belong to dihedral (D4 and D5) or cyclic groups (C4 or C5). The sepals of some monocot flowers develop to replicate the petals, thus, superficially, certain monocots can appear to have rotational symmetry of order 6 and belong to either symmetry group D6 or C6. It must be remembered however, that flower symmetry is rarely perfect in the way that geometric symmetry is. The general layout of a flower belongs to the above symmetry groups, but an individual flower will not show exact symmetry. The Brassicaceae are a medium-sized and economically important family of flowering plants (angiosperms), informally known as the mustards, the mustard flowers, the crucifers, or the cabbage family. The name Brassicaceae is derived from the included genus Brassica. An older name, Cruciferae (English /kruːˈsɪfəri/), meaning "cross-bearing", describes the four petals of mustard flowers, which resemble a cross; it is one of eight plant family names without the suffix -aceae that are authorized alternative names (according to ICBN Art. 18.5 and 18.6 Vienna Code); thus both Cruciferae and Brassicaceae are used. The family contains 372 genera and 4060 accepted species.[2] The largest genera are Draba (440 species), Erysimum (261 species), Lepidium (234 species), Cardamine (233 species), and Alyssum (207 species). The family contains the cruciferous vegetables, including species such as Brassica oleracea (e.g., broccoli, cabbage, cauliflower, kale, collards), Brassica rapa (turnip, Chinese cabbage, etc.), Brassica napus (rapeseed, etc.), Raphanus sativus (common radish), Armoracia rusticana (horseradish), Matthiola (stock) and the model organism Arabidopsis thaliana (thale cress). Pieris rapae and other butterflies of the family Pieridae are some of the best-known pests of Brassicaceae species planted as commercial crops. The Fabaceae, Leguminosae or Papilionaceae,[6] commonly known as the legume, pea, or bean family, are a large and economically important family of flowering plants. It includes trees, shrubs, and perennial or annual herbaceous plants, which are easily recognized by their fruit (legume) and their compound, stipulated leaves. The family is widely distributed, and is the third-largest land plant family in terms of number of species, behind only the Orchidaceae and Asteraceae, with about 751 genera and some 19,000 known species[7][8][9] . The five largest of the genera are Astragalus (over 3,000 species), Acacia (over 1000 species), Indigofera (around 700 species), Crotalaria (around 700 species) and Mimosa (around 500 species), which constitute about a quarter of all legume species. The ca. 19,000 known legume species amount to about 7% of flowering plant species.[8][10] Fabaceae is the most common family found in tropical rainforests and in dry forests in the Americas and Africa.[11] Recent molecular and morphological evidence supports the fact that the Fabaceae is a single monophyletic family.[12] This point of view has been supported not only by the degree of interrelation shown by different groups within the family compared with that found among the Leguminosae and their closest relations, but also by all the recent phylogenetic studies based on DNA sequences.[13][14][15] These studies confirm that the Fabaceae are a monophyletic group that is closely related to the Polygalaceae, Surianaceae and Quillajaceae families and that they belong to the order Fabales.[16] Along with the cereals, some fruits and tropical roots a number of Leguminosae have been a staple human food for millennia and their use is closely related to human evolution.[17] A number are important agricultural and food plants, including Glycine max (soybean), Phaseolus (beans), Pisum sativum (pea), Cicer arietinum (chickpeas), Medicago sativa (alfalfa), Arachis hypogaea (peanut), Lathyrus odoratus (sweet pea), Ceratonia siliqua (carob), and Glycyrrhiza glabra (liquorice). A number of species are also weedy pests in different parts of the world, including: Cytisus scoparius (broom), Robinia pseudoacacia (black locust), Ulex europaeus (gorse), Pueraria lobata (kudzu), and a number of Lupinus species. In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often (but not always) different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture. Typically, they also look different from the parts of the flower, such as the petals and/or sepals. The state of having bracts is referred to as bracteate or bracteolate, and conversely the state of lacking them is referred to as ebracteate and ebracteolate, without bracts. DESCRIPTION OF SOME IMPORTANT FAMILIES Fabaceae This family was earlier called Papilonoideae, a subfamily of family Leguminosae. It is distributed all over the world. 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. Floral characters Inflorescence: racemose Flower: bisexual, zygomorphic Calyx: sepals five, gamosepalous; 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). 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 small trees Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid or hollow, hairy or glabrous, underground stem in potato (Solanum tuberosum) Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate Floral Characters Inflorescence : Solitary, axillary or cymose as in Solanum Flower: bisexual, actinomorphic Calyx: sepals five, united, persistent, valvate aestivation Corolla: petals five, united; valvate aestivation Androecium: stamens five, epipetalous Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen with many ovules Fruits: berry or capsule Seeds: many, endospermous Floral Formula: (refer to the book) Economic Importance Many plants belonging to this family are source of food (tomato, brinjal, potato), spice (chilli); medicine (belladonna, ashwagandha); fumigatory (tobacco); ornamentals (petunia). Lilaceae 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 Androcium: stamen six, (3+3) Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with many ovules; axile placentation Fruit: capsule, rarely berry Seed: endospermous Floral Formula: ⊕ P3+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). Pisum sativum (pea) plant : (a) Flowering twig (b) Flower (c) Petals (d) Reproductive parts (e) L.S.carpel (f) Floral diagram Allium cepa (onion) plant : (a) Plant (b) Inflorescence (c) Flower (d) Floral diagram