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SEXUAL REPRODUCTION IN FLOWERING PLANTS, FOR KITE-VICTERS ONLINE CLASS (PLUS TWO BOTANY)-VII, , 7, , INTRODUCTION,  Reproduction ensures continuity of species generation after generations as the older, individuals undergo senescence and die.,  Flowering plants show sexual mode of reproduction and produce flowers as their reproductive, structure after the completion of vegetative phase .,  A flower is considered as a modified shoot., o The thalamus of a flower is the enlarged and condensed axis., o It has nodes and very short internodes., o It bears the floral whorls such as calyx,corolla,androecium and gynoecuim at the nodes., Pre-fertilisation: Structures and Events,  Several structural and hormonal changes lead to formation and development of the floral, primordium.,  Inflorescence is formed that bears floral, buds and then flower.,  A typical angiospermic flower consists of, four whorls of floral appendages, attached on the receptacle/thalamus.,  They are calyx, corolla, androecium and, gynoecium,  In flowers, male (androecium) and female, (gynoecium) reproductive structures later, produce male and female gametes., Stamen, Microsporangium and Pollen Grain,  Stamen consists of long and slender stalk called filament, and terminal bilobed structure called anther.,  A typical angiosperm anther is bilobed with each lobe, having two theca (chamber).,  In general the anther is four-sided structure consisting of, four microsporangia, two in each lobes.,  Microsporangia develop further and become pollen sacs, which contain pollen grains., , Structure of microsporangium,  Microsporangium is generally surrounded by four layered wall- the epidermis, endothecium,, middle layer and tapetum.,  Innermost layer, tapetum nourishes the developing pollen grains.,  The cells of the tapetum are multinucleated (due to endomitosis) and have dense cytoplasm., Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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 The outer three wall layers perform the function of protection and help in dehiscence of, anther to release the pollen, ,  Sporogenous tissues, o It is compactly arranged homogenous cells which are present at centre of each, microsporangium when the anther is young., Microsporogenesis, o The process of the formation of microspores (pollen grains) from microspore mother cells, (MMC) by reduction division is called microsporogenesis., o The cells of sporogenous tissues undergo meiotic division to form microspore tetrad., o As the anther mature and dehydrate, the microspore dissociate and develops into pollen, grains, #############, , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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SEXUAL REPRODUCTION IN FLOWERING PLANTS, FOR KITE-VICTERS ONLINE CLASS (PLUS TWO BOTANY)-VIII, , 8, , POLLEN GRAIN,  Pollen grains represent the male gametophytes.,  Pollen grains have 2 layered wall,outer exine and inner intine., EXINE, o Made up of sporopollenin- most resistant organic matter known., o It can withstand high temperatures and strong acids and alkali., o No enzyme can degrade sporopollenin, o Presence of sporopollenin helps the pollen to be preserved even in fossils., INTINE., o Thin and continuous layer made up of cellulose and pectin, o A plasma membrane surrounds cytoplasm of pollen grain., o Germ pores -Apertures or openings on exine where sporopollenin is absent., o After pollination pollen tube emerges through germ pore., MATURE POLLEN,  A mature pollen consist of 2 cells with nucleus (Vegetative cell and Generative cell), VEGETATIVE CELL, o Larger cell of the pollen grain with abundant food reserves, o Contains large irregular nucleus, o The function of the vegetative cell is to provide the medium for the movement of male, gametes inside the pollen tube, GENERATIVE CELL, o Smaller cell of the pollen grain and contain minimum amount of cytoplasm, o It divides mitotically to produce two functional male gametes., o In about 60% of angiosperms, pollen grains are liberated at 2-celled stage., o In about 40% flowering plants, the generative cell divides mitotically to give rise to the, two male gametes before pollen grains are shed at 3-celled stage.,  Economic importance of Pollen grains,  Pollen grains of many species (e.g Parthenium) cause severe allergies and bronchial diseases in, some people and leads to chronic respiratory disorders– asthma, bronchitis, etc.,  Pollen grains are rich in nutrients and are used as pollen tablets as food supplements.,  Pollen consumption increases the performance of athletes and race horses., , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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Pollen Viability,  Pollen viability denotes the ability of pollen to complete post-pollination events and to effect, fertilization.,  Pollens of wheat and rice remain viable for 30 minutes. Pollens of same other plants may, remain viable for several months.,  Pollen grains of large number of species are stored in liquid nitrogen at temperature – 1960 ,, and can be used as pollen bank., ,, #############, , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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SEXUAL REPRODUCTION IN FLOWERING PLANTS, FOR KITE-VICTERS ONLINE CLASS (PLUS TWO BOTANY)-IX, , 9, , The Pistil, Megasporangium (Ovule) and Embryo sac,  Gynoecium represents female reproductive part of the flower.,  Gynoecium may consists of single carpel (monocarpellary) or more than one carpel, (polycarpellary),  Carpels may be fused (syncarpous Eg.Papaver) or free (apocarpous Eg.Michelia).,  Each pistil has three parts the stigma(terminal landing surface for pollen grain), style, (elongated slender part)and ovary (swollen basal portion of the carpel).,  Inside the ovary is ovarian cavity (locule). The placenta is located inside the ovarian cavity.,  Megasporangium (ovule) arises from placenta., MEGASPORANGIUM (OVULE),  Ovule is a small structure attached to placenta.,  Funicle – stalk by which ovule is attached to placenta  The point of attachment of funicle, with the body of ovule is called hilum.,  The main body of the ovule is covered with one or two envelopes called integuments.,  Integuments leave an opening at the top of the ovule called micropyle.,  The body of the ovule shows two ends: the basal end, often called the chalazal end and the, upper end is called micropylar end.,  Parenchymatous tissue enclosed inside the integument is called nucellus, MEGASPOROGENESIS,  The process of formation of megaspore from megaspore mother cell by meiotic division is, known as megasporogenesis. This process takes place in ovule,  Ovule differentiates a single megaspore mother cell (MMC) in the micropylar region of, nucellus.,  MMC undergoes meiotic division that results into the production of four megaspores.,  In most of the flowering plants three megaspores degenerate and remaining single megaspore, develops into female gametophyte (embryo sac).,  The nucleus of functional megaspore divides mitotically to form two nuclei which move to, opposite poles to form 2-nucleate embryo sac.,  Two more sequential mitotic division results into 8-nucleate embryo sac.,  One nucleus from each pole then moves towards the middle of the large central cell and forms, a pair of polar nuclei.,  The three nuclei of the micropylar end form the egg appaatus (one central egg and two lateral, synergids) and the rest three at the chalazal end are called antipodal cells.,  At maturity ,embryosac is 8-nucleate and 7 celled., , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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10, , SEXUAL REPRODUCTION IN ANGIOSPERMS, FOR KITE-VICTERS ONLINE CLASS-X, , Pollination, , 00, ,  Transfer of pollen grains from anther to stigma., , Autogamy–, o, o, o, o, o, o, o, , Transfer of pollen grains from anther to stigma of same flower., It requires synchronous maturation of anther and stigma., Cleistogamous Flower –, flower which do not open., cleistogamous flowers are autogamous as there is no chance of transfer of foreign, pollen to the stigma., Cleistogamous flowers ensure the development of seeds even in the absence of, pollinators. e.g Viola (common pansy), Oxalis, and Commelina., Chasmogamous Open flowers with exposed anther and stigma., , Geitonogamy, o, o, o, o, o, , Transfer of pollen grains from anther of a flower to stigma of another flower of, same plant., Geitonogamy is functionally a type of cross-pollination involving a pollinating agent., Genetically it is similar to autogamy since the pollen grains coming from the same, plant, Xenogamy–, Transfer of pollen grain from anther to the stigma of a different plant of the same, species., , Agents of pollination,  Pollinating agents includes abiotic (water, wind) and biotic (insects, butterfly, honey bee, etc.),  Large number of pollen grains are produced by plants using abiotic mode of pollination to, compensate the loss of pollen grains during transfer., , Adaptations in flowers for Pollination, WIND POLLINATION, , , , , , , , Pollen grains light weighted and non- sticky., Have well-exposed stamens (so that the pollens are easily dispersed into wind currents), Large and feathery stigma helps to receive pollen grains moving in the air., In wind pollinating plants numerous flowers are packed into an inflorescence., Eg. : Corn cob,Rice,Maize,Papaya ,Date palm, , WATER POLLINATION, , , , , , , , Pollen grains protected by mucilaginous covering., Large and ribbon shaped pollen grains in some species., They do not produce nectar/honey, Eg : Fresh water plants- Vallisneria, Hydrilla, Marine Plants, All aquatic plants are not pollinated by water., , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode, , - Zostera

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 In vallisneria, the female flower reach the surface of water by the long stalk and the, male flower or pollen grains are released into the surface of water.,  Eichornia and water lilly are insect pollinating hydrophytes., INSECT POLLINATION, , , , , , , , The flowers pollinated by insects are bright-coloured and produce nectar., The fragrance of the flowers attracts the insects., The pollen grains are sticky, large, and rough so that stick to the body of the insects., The stigmas are also sticky so that the pollens depositing are not dispersed., Eg.Cucumber,Sunflower,Aster, , Certain rewards to pollinators:,  Pollen and nectar are the primary rewards offered by flowers to visiting animals.,  Some flowers provide safe place for laying eggs., Eg. Amorphophallus, Yucca,  Many insects may consume pollen or the nectar without bringing about pollination., Such floral visitors are referred to as pollen/nectar robbers., , ***********, , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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SEXUAL REPRODUCTION IN ANGIOSPERMS, FOR KITE-VICTERS ONLINE CLASS-XI, , Outbreeding Devices, , 11, 00, ,  Many plants have developed various mechanisms to discourage self-pollination and, encourage cross pollination - these are called as outbreeding devices,  Pollen release and stigma receptivity not synchronized (maturation of pollen and stigma at, different times – Dichogamy).,  Anther and stigma are placed at different position –(Herkogamy).,  Pollen grains of a flower do not germinate on the stigma of the same flower.(Self, sterility/self incompatibility),  Production of unisexual flowers.(Dicliny), , Pollen pistil interaction, ,  The pollen-pistil interaction begins with pollination, followed by pollen adhesion to the, stigma,  All pollinations do not lead to successful fertilization because ,the pistil of a flower has to, recognize the pollen of the same species.,  The pistil has ability to recognize the compatible pollen to initiate post pollination events, that leads to fertilisation., , Events of pollen-pistil interaction proceed as follows:, o The landing of true pollen on the compatible pistil., o Compatible pollens absorb water and nutrients from the surface of stigma,, germinate and produce pollen tube., o Germination of pollen and formation of pollen tube where pollen grains release its, contents., o Pollen tube grows through the style of the pistil towards the ovary., o After reaching the ovary, the pollen tube enters the ovule through micropylar end., o It then enters one of the synergids through the filiform apparatus present at, micropylar end., , ***********, Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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SEXUAL REPRODUCTION IN FLOWERING PLANTS, FOR KITE-VICTERS ONLINE CLASS (PLUS TWO BOTANY)-XII, , 12, , ARTIFICIAL HYBRIDIZATION,  It is one of the innovative methods of the crop improvement program.,  In artificial hybridization,only desired pollen grains are are used for pollination and, fertilization.,  Emasculation :, o Removal of anther from a bisexual flower before it releases pollen grain., o In the case of unisexual flowers, this step is not necessary.,  Bagging :, o Bagging is the protection of emasculated flower from contamination by undesirable pollen, grains, o Here the flower is covered by a bag, until the flower attains receptivity., o In unisexual flowers, bagging is done before the flowers are open., o Once the flower attains stigma receptivity, the desired pollens are dusted on the stigma., DOUBLE FERTILISATION,  After entering into one of the synergids,the pollen tube releases two male gametes in the, cytoplasm of the synergid.,  One male gamete (n) fuses with egg (n) and form a zygote .It is called Syngamy.,  Other male gamete fuses with two polar nuclei to produce a triploid primary endosperm, nucleus (PEN). This fusion is called tripple fusion.,  Since two types of fusion takes place in an embryo sac the phenomenon is called double, fertilisation.,  The PEN develops into the endosperm and zygote develops into embryo., iii.POST FERTILISATION EVENTS.,  This phase includes endosperm and embryo development, maturation of ovules into seeds and, ovary into fruits., ENDOSPERM,  The primary endosperm cell divides many time to forms a triploid endosperm tissue having, reserve food materials.,  An endosperm forms the surrounding tissue of the growing embryo and their main function, is to provide nutrients to the growing embryo.,  Two types of endosperm development are, (i) Free nuclear type (common method), o In this type, the cell divisions are free-nuclear divisions where each cell division is not, followed by cell wall formation., o They may or may not form a cell wall towards later stages. Eg.Coconut, (ii) Cellular type, o Cell wall formation follows each cell division., o Thus, the endosperm divides into many segments., #############, , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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SEXUAL REPRODUCTION IN ANGIOSPERMS, , 13, , FOR KITE-VICTERS ONLINE CLASS-XIII, , 3, , Embryo,  Embryo develops at the micropylar end of the embryo sac where the zygote is located.,  Development of zygote to embryo starts only after endosperm formation has started.,  This is because endosperm provides nutrition needed for the embryo to develop., Embryogeny,  Stages of embryo development are same in both monocot & dicot plants,  The zygote gives rise to the proembryo and subsequently to the globular, heart-shaped, and mature embryo., , 3, , , , , , , , , Dicotyledonous embryo has the following important parts:, 1. Embryonal axis - Main axis of the embryo which divides into different regions, 2.Cotyledons/embryonic leaves provide nourishment to the developing radicle & plumule, 3.Plumule(upper end of the embryonal axis)and radicle(lower end of the embryonal axis), 4. Epicotyle - Part of embryonal axis above the cotyledons which terminates at plumule, 5 Hypocotyle - Part of embryonal axis below the cotyledons which terminates at radicle, Dicot Embryo, Monocot Embryo, ,  Monocotyledonous embryo has the following parts,  1. Embryonal axis - Main axis of the embryo which divides into different regions,  2.Single cotyledon called scutellum located at one side of the axis.,  3.Plumule(upper end of the embryonal axis)and radicle(lower end of the embryonal axis),  4.Coleorrhiza: undifferentiated sheath covering radical & root cap,  5.Coleoptile: sheath covering plumule, Seed, Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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 Seed is a fertilized ovule.,  Integuments of ovule harden to form Seed coat, however micropyle is still present on, the seed coat as minute opening for entry of water and oxygen..,  In dicot plants the seed coat has 2 layers, thick outer layer(testa) thin inner, layer(tegmen),  Hilum is the scar on seed coat through which the seed was attached to the fruit.,  Perisperm : Remnants of nucellus that is persistent in the seed., Eg. Black pepper,Sugar beet.,  In some seeds general metabolic activity of embryo slows down and seeds enter into a, state of inactivity called Dormancy., ,  Seeds are extremely useful in agriculture. Some of the important applications of seeds, are:,  Help plant species to be colonized in different areas,  Provide nourishment to young seedlings,  Ensure protection to the young embryo,  Results in variations with new genetic combinations,  Can be easily stored for future usage, Fruits,  Fertilized and mature ovaries are called fruits,  The wall of ovary develops into wall of fruit called pericarp.,  In some fruits the pericarp is further differentiated into three layers, namely:,  Epicarp: Outermost layer, forms the peel.,  Mesocarp: Middle layer, fleshy, edible portion of the fruits,  Endocarp: Innermost layer, inner rough portion where the seed is accommodated., ,  In true fruits only ovary contributes in fruit formation but in false fruit thalamus also, contributes in fruit formation(Eg. Apple,Strawberry,Cashew,  Fruits formed without pollination and fertilization are called Parthenocarpic, fruits.Eg.Banana,  Parthenocarpic fruits are generally seedless in nature, ***********, Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode

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SEXUAL REPRODUCTION IN ANGIOSPERMS, FOR KITE-VICTERS ONLINE CLASS-XIV, , 14, , Apomixis,  Apomixis is a mechanism to produce seeds without fertilization.,  This mechanism produces clones, hence can be considered as a form of asexual, reproduction,  Apomixis can occur in a number of ways, some of which are mentioned below:,  Nucellar cells which are diploid & located outside the embryo sac continuously, divide and enter inside embryo sac and later develop into embryos.,  Sometimes, the egg cell is not formed as a result of reduction division, hence, diploid. This diploid egg cell later directly develops into an embryo.,  Apomixis is extremely useful these days because of the following reasons:,  Clonal reproduction through seeds,  New hybrids produced in lesser time.,  During apomixis, chromosomal segregation and recombination does not, occur. So,characters are stable for several generations, , Polyembryony,  Occurrence of more than one embryo in a seed,  Often associated with apomixis. Ex: Citrus, groundnut,  In many citrus and mango varieties, some of the nucellar cells surrounding, the embryo sac start dividing,protrude into the embryo sac and develop, into embryos.,  Polyembryony plays a main role in plant breeding and horticultur e, , ***********, , Prepared by Ismail Parambath,KKM Govt.HSS,Orkatteri,Kozhikkode