Plant reproduction

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Plant reproduction:

Plant reproduction 1

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Angiosperms Meiosis Fertilization Key Haploid Diploid Sporophyte Gametophytes Meiosis Alternation of Generations Microsporangium Megasporangium Meiosis occurs in sporangia of sporophytes Microspore Megaspore 2

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Angiosperms Meiosis Fertilization Key Haploid Diploid Sporophyte Gametophytes Meiosis Alternation of Generations Microspore Megaspore Pollen Embryo sac Microsporangium Megasporangium Spores divide by mitosis and develop into mature gametophytes 3

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Angiosperms Meiosis Fertilization Key Haploid Diploid Sporophyte Gametophytes Meiosis Alternation of Generations Microspore Megaspore Pollen Embryo sac Microsporangium Megasporangium Specialized gametophyte cells divide by mitosis to form gametes Egg 2 sperm 4

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Angiosperms Meiosis Fertilization Key Haploid Diploid Sporophyte Gametophytes Meiosis Microspore Megaspore Pollen Embryo sac Microsporangium Megasporangium Zygote Embryo Seedling Egg 2 sperm Endosperm Alternation of Generations Gametes fuse during fertilization to produce a zygote 5

Flowers:

sepal Flowers Sepals and petals are modified leaves. Sepals are outermost layer that protects developing flower 6

Flowers:

Petals can help to attract animal pollinators petal Flowers

Flowers:

A stamen is the male structure of the flower. anther produces pollen grains filament supports the anther stamen filament anther Flowers

Flowers:

carpel style stigma ovary The innermost layer of a flower is the female carpel. stigma is sticky tip style is tube leading from stigma to ovary ovary produces female gametophyte Flowers

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A sporophytes’ male reproductive structures: Stamen Anther Filament Flowers 10

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A sporophytes’ male reproductive structures: Each anther contains multiple pollen sacs (microsporangia) Flowers 11

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A sporophytes’ male reproductive structures: Each pollen sac contains multiple diploid microsporocytes (microspore mother cells) Flowers 12

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A sporophytes’ male reproductive structures: Each microsporocyte divides by meiosis to produce 4 haploid microspores Flowers 13

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A sporophytes’ male reproductive structures: Each microspore divides once by mitosis to form an immature male gametophyte (pollen grain) A single tube cell encloses a single generative cell Flowers 14

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A sporophytes’ male reproductive structures: The pollen grain matures into an adult male gametophyte when its generative cell divides by mitosis to produce two sperm The adult male gametophyte is a fully mature, independent plant with only 3 cells Flowers pollen grain 15

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The formation of microspores inside the microsporangia (or pollen sacs) of seed plants. A diploid cell in the microsporangium, called a microsporocyte or a pollen mother cell, undergoes meiosis and gives rise to four haploid microspores. Each microspore then develops into a pollen grain (the micro gametophyte). Microsporogenesis and male gametophyte

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Formation of generative and vegetative cells Development of male gametophyte

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A sporophytes’ female reproductive structures: Carpel Stigma Style Ovary Ovule Receptacle Flowers 18

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A sporophytes’ female reproductive structures: Each ovule contains a megasporangium Each megasporangium contains a megasporocyte (megaspore mother cell) In the ovules of angiosperms, megasporogenesis takes place within a structure called a nucellus Flowers 19

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A sporophytes’ female reproductive structures: A megasporocyte divides by meiosis to form 4 cells Only 1 of the 4 cells survives: the megaspore It is the megaspore farthest from the micropyle of the ovary that survives . Flowers 20

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Female gametophyte

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A sporophytes’ female reproductive structures: The megaspore’s nucleus divides 3 times: giving 1 248 nuclei Membranes then partition the 8-nucleate immature gametophyte cell into 7 smaller cells (one with 2 nuclei) Flowers 22

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A sporophytes’ female reproductive structures: The 7 cells: 1 egg 1 cell with 2 polar nuclei 5 other cells The 7 cells comprise the mature, completely dependent female gametophyte (embryo sac) Flowers 23

Pollination:

Pollination Flowering plants pollinated when pollen grains land on stigma. Wind pollinated flowers have small flowers and large amounts of pollen. Animal pollinated flowers have larger flowers and less pollen. 24

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Genetic self-incompatibility, gauged by S-genes Self incompatibility 25

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Genetic self-incompatibility, gauged by S-genes Self incompatibility 26

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Genetic self-incompatibility, gauged by S-genes Self incompatibility 27

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Depending upon its place of entry, three types of fertilization are : Porogamy :- Here the entry of the pollen tube into the ovule takes place through the micropyle . Chalazogamy : -In plants like Casuarina , the entry of pollen tube takes place through the chalaza . Mesogamy :- In Cucurbita , pollen tube enters the ovule through the integuments . Entry of pollen tube in the ovule; A. Porogamy, B. Chalazogamy, C. Mesogamy Path of pollen tube into ovule

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A pollen grain disperses to a stigma (pollination) The tube cell grows into a pollen tube Fertilization takes place within the flower. 29

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Double fertilization of angiosperms The 2 sperm cells travel down the pollen tube to the embryo sac 30

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Double fertilization of angiosperms The 2 sperm cells travel down the pollen tube to the embryo sac 31

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Double fertilization of angiosperms The 2 sperm cells travel down the pollen tube to the embryo sac 32

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Double fertilization of angiosperms 1 sperm fuses with the egg (fertilization) 1 sperm fuses with the polar nuclei to form the first cell of the endosperm (triploid) 33

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The surrounding ovary grows into a fruit. Each ovule becomes a seed. Development of fruit 34

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Development of ovule into seed with developing embryo and nutrient supply Endosperm development Triploid nucleus divides, forming multinucleate “supercell”, the endosperm, which becomes multicellular as cell membranes & walls are laid down Nutrient-rich endosperm provides nourishment for developing embryo Embryo development Asymmetric transverse mitotic division produces terminal cell & basal cell Terminal cell divides, gives rise to proembryo Cotyledons form as bumps on proembryo, grow to envelope the embryo Embryo elongates; embryonic apical root and shoot meristems differentiate (root meristem develops partly from basal cell in some species); embryonic primary meristems differentiate Transverse divisions of basal cell gives rise to suspensor that will anchor embryo to ovule integuments, transfer nutrients from parent plant and, in some plants, from endosperm

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Development of the seed and fruit The ovule integuments become the seed coat. Tissues of the ovary (and sometimes the receptacle) become the fruit 36

Post fertilization changes:

Post fertilization changes Flower part Post fertilization change 37

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Development of the seed and fruit Simple fruit - single carpel of one flower Aggregate fruit - many separate carpels of one flower Multiple fruit - many carpels of many flowers Pineapple Raspberry Pea Stamen Carpel (fruitlet) Stigma Each segment develops from the carpel of one flower Stamen Carpels Flower Stigma Ovule Seed There are many kinds of fruits 38

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