FEMALE REPRODUCTIVE SYSTEM

Ovaries

The ovaries are a pair of small glands about the size and shape of almonds, located on the left and right sides of the pelvic body cavity lateral to the superior portion of the uterus. Ovaries produce female sex hormones such as estrogen and progesterone as well as ova (commonly called "eggs"), the female gametes. Ova are produced from oocyte cells that slowly develop throughout a woman’s early life and reach maturity after puberty. Each month during ovulation, a mature ovum is released. The ovum travels from the ovary to the fallopian tube, where it may be fertilized before reaching the uterus.

Fallopian Tubes

The fallopian tubes are a pair of muscular tubes that extend from the left and right superior corners of the uterus to the edge of the ovaries. The fallopian tubes end in a funnel-shaped structure called the infundibulum, which is covered with small finger-like projections called fimbriae. The fimbriae swipe over the outside of the ovaries to pick up released ova and carry them into the infundibulum for transport to the uterus. The inside of each fallopian tube is covered in cilia that work with the smooth muscle of the tube to carry the ovum to the uterus.

Uterus

The uterus is a hollow, muscular, pear-shaped organ located posterior and superior to the urinary bladder. Connected to the two fallopian tubes on its superior end and to the vagina (via the cervix) on its inferior end, the uterus is also known as the womb, as it surrounds and supports the developing fetus during pregnancy. The inner lining of the uterus, known as the endometrium, provides support to the embryo during early development. The visceral muscles of the uterus contract during childbirth to push the fetus through the birth canal.

Vagina

The vagina is an elastic, muscular tube that connects the cervix of the uterus to the exterior of the body. It is located inferior to the uterus and posterior to the urinary bladder. The vagina functions as the receptacle for the penis during sexual intercourse and carries sperm to the uterus and fallopian tubes. It also serves as the birth canal by stretching to allow delivery of the fetus during childbirth. During menstruation, the menstrual flow exits the body via the vagina.

Vulva
The vulva is the collective name for the external female genitalia located in the pubic region of the body. The vulva surrounds the external ends of the urethral opening and the vagina and includes the mons pubis, labia majora, labia minora, and clitoris. The mons pubis, or pubic mound, is a raised layer of adipose tissue between the skin and thepubic bone that provides cushioning to the vulva. The inferior portion of the mons pubis splits into left and right halves called the labia majora. The mons pubis and labia majora are covered with pubic hairs. Inside of the labia majora are smaller, hairless folds of skin called the labia minora that surround the vaginal and urethral openings. On the superior end of the labia minora is a small mass of erectile tissue known as the clitoristhat contains many nerve endings for sensing sexual pleasure.

Breasts and Mammary Glands

The breasts are specialized organs of the female body that contain mammary glands, milk ducts, and adipose tissue. The two breasts are located on the left and right sides of the thoracic region of the body. In the center of each breast is a highly pigmented nipple that releases milk when stimulated. The areola, a thickened, highly pigmented band of skin that surrounds the nipple, protects the underlying tissues during breastfeeding. The mammary glands are a special type of sudoriferous glands that have been modified to produce milk to feed infants. Within each breast, 15 to 20 clusters of mammary glands become active during pregnancy and remain active until milk is no longer needed. The milk passes through milk ducts on its way to the nipple, where it exits the body.

           

The Reproductive Cycle

The female reproductive cycle is the process of producing an ovum and readying the uterus to receive a fertilized ovum to begin pregnancy. If an ovum is produced but not fertilized and implanted in the uterine wall, the reproductive cycle resets itself through menstruation. The entire reproductive cycle takes about 28 days on average, but may be as short as 24 days or as long as 36 days for some women.

Oogenesis and Ovulation

Under the influence of follicle stimulating hormone (FSH), and luteinizing hormone (LH), the ovaries produce a mature ovum in a process known as ovulation. By about 14 days into the reproductive cycle, an oocyte reaches maturity and is released as an ovum. Although the ovaries begin to mature many oocytes each month, usually only one ovum per cycle is released.

Fertilization

Once the mature ovum is released from the ovary, the fimbriae catch the egg and direct it down the fallopian tube to the uterus. It takes about a week for the ovum to travel to the uterus. If sperm are able to reach and penetrate the ovum, the ovum becomes a fertilized zygote containing a full complement of DNA. After a two-week period of rapid cell division known as the germinal period of development, the zygote forms an embryo. The embryo will then implant itself into the uterine wall and develop there during pregnancy.

Menstruation

While the ovum matures and travels through the fallopian tube, the endometrium grows and develops in preparation for the embryo. If the ovum is not fertilized in time or if it fails to implant into the endometrium, the arteries of the uterus constrict to cut off blood flow to the endometrium. The lack of blood flow causes cell death in the endometrium and the eventual shedding of tissue in a process known as menstruation. In a normal menstrual cycle, this shedding begins around day 28 and continues into the first few days of the new reproductive cycle.

Pregnancy

If the ovum is fertilized by a sperm cell, the fertilized embryo will implant itself into the endometrium and begin to form an amniotic cavity, umbilical cord, and placenta. For the first 8 weeks, the embryo will develop almost all of the tissues and organs present in the adult before entering the fetal period of development during weeks 9 through 38. During the fetal period, the fetus grows larger and more complex until it is ready to be born.

Lactation

Lactation is the production and release of milk to feed an infant. The production of milk begins prior to birth under the control of the hormone prolactin. Prolactin is produced in response to the suckling of an infant on the nipple, so milk is produced as long as active breastfeeding occurs. As soon as an infant is weaned, prolactin and milk production end soon after. The release of milk by the nipples is known as the “milk-letdown reflex” and is controlled by the hormone oxytocin. Oxytocin is also produced in response to infant suckling so that milk is only released when an infant is actively feeding. 




HOW DID LIFE STARTED ON THE EARTH ?

Scientists do not know how life began on Earth. They do know that the early Earth’s atmosphere was very different from the atmosphere now.

In 1952, Stanley Miller was working with Harold C. Urey designed an experiment to see how complex organic molecules might have formed under the conditions of early Earth. They believed the early Earth atmosphere would have been composed of methane, ammonia, hydrogen and water vapor. They sealed these gases in an airtight container, and then exposed the gases to sparks of electricity to simulate lightning. They continued the lightning for a week, and by the end, a reddish-brown substance had coated the walls of the container. This substance contained 11 of the 20 amino acids used by life on earth. Since Miller and Urey performed this experiment, its results have been confirmed many times by other scientists. Many scientists now believe that the early Earth’s atmosphere was composed of carbon dioxide, nitrogen and water vapor.

Modern experiments with this mixture of gases produce similar results suggesting that early conditions on Earth produced complex organic molecules that probably became the basis for the development of more complex organisms. However, scientists have not been able to replicate the formation of even simple organisms, or anything that can really replicate itself. There are several theories as to how the amino acids might have made the leap into the complex, self-replicating life we see today.

Metabolism - First

Some scientists believe that metabolism, in other words - the ability to break down carbon dioxide in the presence of a catalyst into small organic molecules - was how the first life developed. These reactions might have evolved to become more complex, and then genetic molecules somehow formed and joined in later. There are many different theories as to exactly what types of molecules and catalysts would have been involved.

Genes - First

Other scientists believe that the first living organisms were genes. These genes were single molecules that had developed in such a way as to be able to catalyze their own replication. This theory seems more likely, since even simple systems such as crystals, have been demonstrated to evolve with modifications that breed true. Some scientists have suggested that certain compositions of clay create the right environment for these reactions to propagate.

RNA

RNA is a complex molecule found in all living things that seems to be able to catalyze its own reproduction. Many scientists believe that simple RNA molecules developed and eventually became more complex and developed into the organisms we see today.

LUCA

Astrobiologists and biochemists want to understand something they call LUCA (the Last Universal Common Ancestor). The idea is that all life on Earth has a common ancestor, kind of like a great-great-great-great grandmother. They search for traits that are common across all life forms and assume that any traits that are common to all life forms today must have been inherited from LUCA, who had them all as well. Biochemists know quite a bit about LUCA and her biochemistry. She stored her genetic information in DNA, she had several hundred proteins performing a variety of functions, and she used the same 20 amino acids we use in our proteins. She used RNA and had some kind of double-layer lipid membrane. She was probably the ancestor of the three kingdoms of life: Archaea, Eukaryotes and Bacteria. LUCA lived at least 2 billion years ago, before there was much oxygen in the atmosphere. She used enzymes containing iron in her metabolic pathways the way much life on early Earth did. Studying how life arose on Earth is useful to astrobiologists, but they keep in mind that the way life formed on Earth is not the only way life could have formed. It is simply one way that it did.

ANNELIDA-COELOM AND COELOMODUCTS

Annelids are the first EUCOELOMETE animals in the evolutionary order. The coelom is SCHIZOCOELOM and it is divided into compartments by intersegmental septa.

Some structures in annelids are arranged segmentally and are described as SEGMENTAL STRUCTURES. Among them there are COELOMODUCTS and NEPHRIDIA . These structures will be useful for the passage of reproductive and excretory products from coelom to the exterior. The segmental structures mainly divided into     

                             I.            COELOMODUCTS

                           II.            NEPHRIDIA

COELOMODUCTS: These are generally wide tubes of MESODERMIC origin and develop as ENVAGINATIONS of coelomic epithelium. Each coelomoduct opens into coelom by a ciliated funnel called COELOMOSTOME which opens out by a genital aperture. Coelomoducts primarily function as GONODUCTS. So these will be limited to the with reproductive structures. In some forms they function as excretory ducts.

NEPHRIDIA: These are generally coiled tubes which are formed by the INVAGINATIONS OF ECTODERM. Each nephridium coummunicates with the outside through a NEPHRIDIOPORE. If the nephridium opens out into the coelom through nephrostome,it is described as OPEN. If it is absent,it is CLOSED. Nephridia without nephridiostome is called PROTONEPHRIDIUM, and if present it is METANEPHRIDIUM. Nephrostome may communicate with prostome of the same segment or anterior to it. Nephridia are primarily excretory(osmoregulation)in function and secondarily serves as REPRODUCTIVE DUCTS(gonoducts).

Nephridia without a nephrostome are considered as PRIMITIVE. In some cases,the closed end of the tube may have SOLENOCYTES which occur singly or in group.

Nephridia with a nephrostome are considered as ADVANCED. In a majority of polychaetes,it opens into coelom through CILIATED NEPHROSTOME.

Based on size, nephridia are classified into MICRONEPHRIDIA and MEGANEPHRIDIA. Generally micronephridia will be more in segments and meganephridia will be anepair per segment.

If nephridium communicates outside through nephridiophore directly, it is termed as EXONEPHRIC,  whose primary function is EXCRETORY and if the terminal ducts ultimately open into alimentary canal it is called as ENDONEPHRIC  nephridia, which are basically OSMOREGULATORY in function.

MIXONEPHRIDIA OR NEPHROMIXIUM:

            Incase of oligocheates and hirudineans the nephridia and coelomoducts are separate structurally and functionally. Where as the nephridia of polycheates and aschiannelids, they function as excretory and reproductive ducts and so they are described as NEPHROMIXIA or MIXONEPHRIDIA

RUTACEAE

RUTACEAE

Systematic Position :

Class :Dicotyledonae

Sub class :Polypetalae

Series : Disciflorae

Order :Geraniales

Family :Rutaceae

Distribution :

Rutaceae comprises 150 genera and 1500 - 1600 species. The plants are widely distributed in both tropical and temperate regions. The members are abundant in South Africa and Australia. In India, the family is represented by 23 genera and over 80 species, predominantly in the tropical and sub tropical Himalayas and the western Peninsular India.

Familiar Plants :

1. Aegle marmelos Bilva or maredu

2. Atlantia monophylla Karunimma.

3. Citrus aurantium (Bitter Orange) Narinja.

4. C. aurantifolia (Sweet lime) Nimma.

5. C. limon (Lemon) Dabba.

6. C. medica (Citron, Nimbu) Madiphalamu

7. C. sinensis (Sweet Orange) Battai.

8. C. reticulata (Loose skinned orange, Santra) Kamala Phalam.

9. C decumara (= C. grandis) Shaddock, Pomelo, Pampara Panasa

10  Feronia elephantum (= Limonia acidissima, Wood apple) Velaga.

11. Murraya koenigii (Curry leaf) Karivepaku.

12. M. paniculata (=M. exotica, Orange jasmine). Pooveiaga

13. Naringi crenulata(= Limonia crenulata) Torra velaga.

14. Ruta graveolens (common rue) Sadapaku

15. Toddalia asiatica (Wild Orange Tree).

16. Chloroxylon swietania (Satin wood) Billukarra.

Habit :

The members are mostly shrubs or small trees, cultivated for their fruits. Herbs are rare (Ruta).

Aegle marmelos and Feronia elephantum are large sized trees.

Murraya exotica is an ornamental shrub with scented flowers. The leaves and bark of the trees are often fragrant due to the presence of oil glands.

Vegetative Characters:

1. Root System : Tap root system, often infected mycorrhizae.

2. Stem : Usually erect, woody, branched, armed with spires or unarmed (Murraya, Evodia). Young shoots are gland dotted.

3. Leaf : Alternate, less frequently opposite (Toddalia), simple, more often pinnately compound as in Murrava. In Citrus sp. leaves are unifoliate with a joint at the junction of leaf blade and winged petiole. In Aegle the leaves are trifoliate. Leaves are typically gland dotted. In many genera, the first leaf of axillary bud modifies into spine.

Floral Characters:

1. Inflorescence : Flowers are clustered into axillary (Citrus Murraya) or in terminal cymes (Clausena, Skimmia) or panicles( Murraya exotica). In some species of Citrus and Triphasia, flowers are axillary and solitary.

2. Flower : Bracteate, bracteolate, pedicellate or sub sessile, complete, bisexual, actinomorphic, hypogynous and pentamerous. A distinct nectar secreting disc is present at the base of the ovary. Flowers are rarely unisexual as in Toddalia, Evodia etc. or may be polygamous as in Feronia. In Ruta, the lateral flowers are tetramerous, while the terminal one is pentamerous.

3. Calyx : Sepals usually five and polysepalous, green in colour and gland dotted. Sometimes 4 or 3 sepals are also found. In zygomorphic flowers, the calyx becomes either tubular or cup shaped. The aestivation is either imbricate or valvate.

4. Corolla : Petals normally five in number, but may be four or three in some members. Petals polypetalous, but gamopetalous condition is seen in Correya (Australia) and Galipea. (America) Aestivation is valvate or imbricate, petals gland dotted and sweet smelling, variously coloured.

5. Androecium : There is great variation in the number of stamens. They may be as many as the number of petals, or twice the number of petals. Stamens 8 - 10, arranged in two whorls. The outer whorl lie opposite to petals and the inner whorl alternates with the outer whorl. This arrangement is known as Obdiplostemonous.

Stamens are some times numberous. In Aegle marmelos upto 60 stamens are present. In Murraya 10 stamens are Present in 5+5 arrangement; stamens are 5 arranged one whorl in the male flowers of Toddalia and Evodia. The anthers are dithecous, basifixed and introse. The connective is usually glandular at the apex.

6. Gynoecium : Ovary superior, manocarpellary (Empleurum), bicarpellary (Murraya) , tricarpellary (Triphasia) , pentacarpellary (Citrus spp.) and syncarpous. Ovary bilocular to Multilocular, or unilocular as in Feronia. Placentation is usually axile, rarely parietal (Feronia), Ovules anatropous. Styles as many as carpels, free or variously united. Stigma terminal, entire or lobed.

7. Fruit : Usually a fleshy berry and is called Hesperidium in Citrus spp. In Aegle marmelos and Feronia the berry is large with a hard epicarp. In Acronychia the fruit is a capsule.

8. Seed : Seeds are generally endospermic, with a straight or curved embryo. Polyembryony is a very common feature of Rutaceae.

9. Pollination : Usually entomophilous. The coloured petals, strong scent, nectar are the sources of attraction for the insects. Cross pollination is favoured by marked protandrous condition of flowers.

Floral formula :

Economic Importance :

The family is of great economic value.

1. Edible fruits : The most important genus of the family, citrus provides various edible fruits like oranges, limes and lemons. They have medicinal value.

(i) Citrus aurantifolia - lime

(ii) C. aurantium - Sour Orange

iii) C. sinensis - Sweet Orange or mausambi

iv) C. limon - lemon.

(v) Aegle marmelos - Wood apple.

vi) Feronia elephantum - Elephant apple.

2. Volatile Oils :

(i) Ruta graveolens : 'oil of rue'- is distilled from leaves and young shoots and is used in perfumery and flavourings.

(ii) Boronia megastigma : 'oil of Boronia' is, distilled from shoots, used in perfumery.

(iii) Amyris balsamifera: Source of a scented oil called West Indian Sandalwood oil.

(iv) Amyris plumieri : ‘Mexican elemi’, an oleoresin is obtained from the bark, Which is used in lacquers.

3. Ornamental Plants :

1. Murraya exotica (Marua)

2. Ruta graveolens (Garden rue)

3. Calodendrum

4. Dictamnus albus

5. Xanthophylum.

6. Toddalia.

7. Atlantia.

4. Other Uses :

1. The leaves of Murraya koenigii are aromatic and are used in flavouring curries.

2. The wood of Chloroxylon swietenia is known as Indian Satin wood and used in making furniture.

3. Timber from Flindersia brayleana is an important hard wood from Australia.

4. Cusparia febrifuga gives 'cusparia bark' which is used as a substitute for quinone.

5. The twigs of Glycosmis pentaphylla and Zanthoxylum alatum are used as chewsticks or tooth brushes in Indochina and Malayasia.

6. The roots of Toddalia asiaticar a spiny shrub, are the source of a yellow dye.

         The family Rutaceae is closely related to Meliaceae Sapindaceae and Anacardiaceae in their external and anatomical features. (heath – like habit, leaf structure, disc formation an obdiplostamonous stamens). Some botanists relate Rutaceae to Euphorbiaceae on account of the ventral raphe in ovule (in some  genera).

BRASSICACEAE

BRASSICACEAE

CRUCIFERAE (OR) MUSTARD FAMILY

Systematic Position

                                                                               Class : Dicotyledonae,

                                                                                 Sub class : Polypetalae,

                                                                                Series : Thalamiflorae,

                                                                        Order : Parietales

                                                                                Family : Brassicaceae.

DISTRIBUTION

Brassicaceae is represented by about 375 genera and 3,200 species. They are Cosmopolitan in distribution, but widely occurs in the Mediterranean region. About 200 species distributed in 25 genera are reported from India.

EXAMPLES

Brassica nigra (mustard)

Brassica rapa (turnip)

Brassica napus (rape seed)

Brassica oleracea Var. capitate (Cabbage)

Brassica oleracea Var. botrytis (Cauliflower)

Brassica oleracea Var. gongylodes (Knol—khol)

Capsella bursa pastoris (Shepherd's purse)

Cheiranthes

Iberis amara (Candy tuft)

Raphanus  sativus (radish)

Subularia aquatica (hydrophyte)

HABITAT

The plants are mostly mesophytes. Subularia aquatica is a hydrophyte.

HABIT

The plants are mostly herbs. They may be annuals (Brassica), biennials (Raphanus) or perennials (Cheiranthus, Cardamine) Many plants are cultivated as they produce vegetables.

VEGETATIVE CHARACTERS

ROOT SYSTEM

The plants possess tap root system. In some biennials the tap root stores food materials and becomes tuberous. It is fusiform in radish and napiform in turnip.

STEM

Stem is aerial, erect and herbaceous. It is extremely condensed in radish and turnip. In Knol—khol, the stem is tuberous due to storage of food materials. In cabbage the terminal bud is the largest vegetative bud.

LEAVES

Leaves are simple, alternate, exstipulate and lyrate. They are cauline (Brassica) or radical (Raphanus). Leaves show reticulate venation. In cabbage, young leaves store food materials.

ANATOMICAL FEATURES

The vegetative parts of the plants contain secretory cells which secrete myrosin. The stomata are surrounded by three unequal subsidiary cells (cruciferous).

FLORAL CHARACTERS

INFLORESCENCE

Inflorescence is mostly terminal and racemose type. It may be simple raceme or corymbose raceme. In Cauliflower the inflorescence is a compound corymb It is fleshy and edible.

FLOWER

Flowers are ebracteate, ebracteolate pedicellate, complete, bisexual, actinomorphic, hypogynous and tetramerous or dimerous. In Cheiranthes the flowers are zygomorphic.

CALYX

It consists of 4 sepals. They are free and arranged in two whorls of two each. The sepals in outer whorl are anteroposterior and that of inner whorl are lateral. Aestivation is valvate or imbricate.

COROLLA

It consists of 4 petals. They are free and present in one whorl. The petals are clawed and arranged diagonally in the form of a cross. (Cruciform corolla). In Lepidium and Capsella bursa the petals are narrow or even absent. Aestivation is valvate

ANDROECIUM

It consists of 6 free stamens arranged in two whorls. The outer whorl consists of two short stamens and the inner whorl is with four long stamens. Thus the stamens are described as tetradynamous. Anthers are dithecous, introrse, basifixed and the dehiscence is longitudinal. Nectaries are present at the base of the stamens.

GYNOECIUM

It consists of 2 carpels. They are fused (syncarpous) and placed transversely in the flower. Ovary is superior and unilocular. It becomes bilocular due to the development of a false septum (replum) from the placenta. Style is terminal and short. Stigma is commissural.

POLLINATION

Pollination is carried out by insects (entomophily). Self pollination is present in Subularia and Cardamine as they posses cleistogamous flowers.

FRUIT

Siliqua (Brassica), silicula (Capsella) or Lomentum (Raphanus).

SEED

Seed is non endospermic with a large embryo having two cotyledons. The cotyledons are oily and completely fills the seed. Testa is mucilagenous.

ECONOMIC IMPORTANCE

1. Seeds of Brassica juncea, B. nigra, B. napus yield mustard oil which is used in cooking.

2. Tuberous storage roots of radish and turnip, vegetative bud of cabbage, inflorescence of cauliflower and tuberous stem of knol khol are used as vegetables.

3. Iberis amara (candy tuft), Cheiranthus are ornamental plants.

4. Mustard seeds are used as condiment.

5, Plants like Nasturtium and Lepidium are medicinally important.

STRUCTURE OF MATURE ANTHER

In a flower, stamen is considered as the male reproductive organ. Each stamen consists of filament, connective and anther. Anther may be monothecous or dithecous. A monothecous anther consists of two locules or two sporangia. So it is said to be bilocular or bisporangiate. A dithecous anther consists of four locules or four sporangia. So it is said to be tetralocular or tetrasporangiate.

Development of microsporangium is eusporangiate. A very young anther in transverse section shows epidermis and archesporium. The archesporial cells divide periclinally giving rise to primary parietal cells. On the outer side and sporogenous cells towards innerside. The cells of the parietal layer divide periclinally and anticlinally forms endothecium, middle layers and tapetum. The cells of the primary sporogenous tissue differentiated into pollen mother cells or microspore mother cells.

                                                 

The anther wall consists of following walls layers.

1.Epidermis: Epidermis is the outermost single layer. It  is compactly arranged and usually protective in function. Epidermal stomata was reported in Alangium.

2.Endothecium: The cells of the endothecium are radially elongated and shows fibrous bands. The fibrous bands are made up of callose an arise from the inner tangential walls. Usually fibrous bands are “U” shaped. Fibrous bands are absent in Hydrocharitaceae, Saprophytes and Cleistogamous flowers. Endothecial thickenings are also absent in Musa, Sesamum, Annona, Ipomea etc but in these members the anther epidermis has deposition of cutin and lignin. The fibrous bands are hygroscopic in nature. Endothecial cells help in the dehiscence of anther at maturity. Because of the presence of fibrous bands, this layer is otherwise called fibrous layer. It is single layered but in Coccinia double layered.

3.Middle layers: Below the endothecium 2-3 layers of cells are present which constitute middle layers. These layers are ephemeral and become crushed by early meiosis in pollen mother cells. These cells act as storage centres for starch.

4.Tapetum: Tapetum is the innermost layer of antherwalls, and it  completely surrounds the sporogenous tissue. The cells contain dense cytoplasm with prominent nuclei. Usually tapetum consists of single layer of cells. As the tapetum completely surrounds the sporogenous tissue major part of it is derived from parietal cells and a small part developed from the sporogenous tissue. Tapetum transports the nutrients to the developing sporocytes. Tapetal cells are pigmented and it is red brown in apple or violet in Anemone

  Base on the behaviour,  two kinds of tapetum were recognised.

a)    Amoeboid tapetum:

 The inner and radial walls of the tapetum break down due to the action of hydrolytic enzymes and their protoplast penetrates between the pollen mother cells and developing pollen grains. After intrusion, they fuse with each other and forms a mass of tapetal periplasmodium. This tapetal plasmodium remains associated with the pollengrains till their maturity. When the anther gets drying up the tapetal periplasmodium gets dehydrated and coated over the surface of pollengrains, thereby helping in the formation of exine. Amoeboid tapetum is considered as the primitive type. It is also called periplasmodial tapetum. Eg:- Alisma, Tradescantia, Typha, Saggitaria, Potamogeton.

b)   Glandular tapetum:

The cells of glandular tapetum remains intact throughout microspore development. They secrete their substances from their innerfaces. Secretary tapetal cells are thin and possess almost all cell organells like mitochondria, plastids, dictyosomes etc. some spherical structures called proubisch bodies are also present. Just before the pollen mother cells undergo meiosis, the walls of the tapetal cells become thick and there is considerable increase in the no. of ribosomes and pro-ubisch bodies with the completion of pollen development proubish bodies pass into the anther locule from the tapetal cells and they are now called ubisch bodies and they coated over the pollengrains Eg:- Higher monocots and many dicots.

Functions of tapetum:

1.   The nutrients are transported through tapetum to the sporogenous tissue.

2.   Tapetum is involved in the synthesis of callose which release microspores in a tetrad by degrading callose wall.

3.   Tapetum plays an important role in the formation of exine.

4.   Pollen kit (Lipids and carotenoids) is formed by tapetal layer. It is a insect attractant & protect pollen from ultra violet.

Technical description of Calotropis gigantea

1.    HABITAT: Mesophyte with xerophytic adaptation.

2.    HABIT    : Shrub.

3.    ROOT    : Not provided.

4.    STEM    : Herbaceous, aerial, erect, cylindrical, solid, glabrous with milky latex.

5.    LEAF     : Cauline (or) ramel, opposite decussate, subsessile, simple,exstipulate, ovate to eliptical, entire, acute, glaucus, reticulate unicostate, coriaceous.

6.    INFLORESCENCE         : Extra axillary, umbelate (or) dichasial cyme.

7. FLOWER IN GENERAL : Pedicellate, bracteate, ebracteolate (or) bracteolate, complete, bisexual, actinomorphic, cyclic, hypogynous, pentamerous, dichlamydeous and heterochlamydeous.

8.    FLOWER IN DETAIL  : 5 Sepals, polysepalous, asendingly imbricate, 5petals, polypetalous, valvate, 5 , epipetalous or gynandrous, exerted stamens, introrse,dithecous anther.

Basifixed in asclepiadoideae behind the stamens the extentions of coralla are present called coronary coralla.

The two anther lobes of adjacent stamens fuses to form a lambda shaped structure called translator mechanism.

Androecium fuses with gynoecium to from gynostegium.

Gynoecium : 2 carpels, bicarpellary, sub-apocarpous, bilocular, superior, marginal placentation, terminal, fuses with pentagonal disc.