Plant Reproduction Why reproduce? Sexual vs. asexual reproduction Sexual reproduction in plants Gametophytes and sporophytes Gymnosperms and angiosperms Asexual reproduction in plants Asexual reproduction using fragments Asexual reproduction using special structures

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Plants Must Reproduce Makes more plants Ensures the continuation of the species Plants can reproduce _________

Sexual Reproduction in Plants Usually needs pollinators (e.g. bees, birds, butterflies). Flowers attract insects, birds, and other animals. _________ Some self-pollinate, while others cannot.

Asexual Reproduction in Plants _________ Does not involve joining of cells. Creates new plants identical to parent plant.

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Sexual Reproduction in Plants Gametes are created by meiosis Meiosis: _________ Gametes produced in special structures called gametangia ……………… Male gametangia: antheridia

Sexual Reproduction in Plants Plants can be bisexual or unisexual Bisexual (monoecious): ___________ Unisexual (dioecious): ____________ Bisexual plants can’t always self-fertilize Sometimes incompatible Cross-fertilization preferred

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Sporophyte _________ Diploid individual Sporocytes (fertile cells) produce haploid spores via meiosis _________

Sexual Reproduction in Plants Liverworts and hornworts ………………. Sperm release and fertilization require moisture (heavy dew or rain) _____________ Spores may germinate immediately upon deposition or undergo a period of dormancy first Liverwort with sporophytes growing from archegonia

Sexual Reproduction in Plants Liverworts and Hornworts

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Sexual Reproduction in Plants Spore plants Includes seed plants and cryptogams (no flowers or seeds) Sporophyte stage dominant Seed plants _______________ Cryptogams Spores shed from plant after producing gametophyte

Sexual Reproduction in Plants There are two groups of seed plants Gymnosperms Angiosperms There are two types of spores Megaspores: large spores; _______________ Microspores: small spores; ______________ Male gametophytes called pollen grains

Gymnosperms and Angiosperms Produce seeds ______________ Passageway through layers on megasporangium Ovule matures as seed One megasporocyte ____________ …………….. ……………… Microspores develop inside microsporangia Pollen grains develop tube to pass sperm to egg ____________

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Gymnosperms Cycads ____________ Pollen grains shed from microsporangia ……………….. Ovule produces pollination droplet Wind-borne pollen grains attach to droplet Droplet pulled back into ovule

Gymnosperms Pines ____________ Sporophyte may become a large tree Pollen has air-filled wings between layers of pollen grain wall Scales on female gametophyte separate and pollen sticks to pollination droplet Droplet …………….. Fertilization occurs around 14 months after pollination

Angiosperms ____________ Seeds enclosed during development in structure called pistil or carpel Gametophytes don’t have archegonia Pollen transferred to surface of megaspore One joins egg and forms the zygote Other joins two nuclei of female gametophyte to form storage tissue that serves as food source for embryo After fertilization, ovule increases to mature seed size

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Angiosperms Some monoecious species Corn Hickory Walnut Pecan Oak

Angiosperms Microspores develop pollen grains (male gametophytes) Forms generative cell and tube cell _____________ Pollination: transfer of pollen grains from anther of stamen to stigma of pistil Some flowers can self-pollinate (e.g. peas and tomatoes) Others need pollinators (e.g. insects) to transfer pollen between flowers

Angiosperms One megasporocyte …………….. ___________ Only one enlarges, others degenerate Enlarged cell divides into seven (with eight nuclei) Three nuclei move to end opposite micropyle (opening where pollen tube enters) and become antipodal cells, which degenerate __________ Last two nuclei help guide pollen tube, then disintegrate

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Angiosperms Pollen passes down the pollen tube, through micropyle, and into gametophyte One sperm fertilizes egg nucleus Other unites with two nuclei in large central cell ___________ Endosperm nucleus Divides into endosperm tissue __________

Angiosperms Ovary, ovules, and zygote grow Embryo develops Seed: __________ Seeds become dormant and form hard seed coats ____________ Seeds …………….. Cotyledons can help digest and absorb endosperm, be food sources themselves, or become photosynthetic leaves above the soil surface

Angiosperms

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Asexual Reproduction in Plants Two basic types ____________

Asexual Reproduction Using Fragments The body of the plant fragments. Pieces fall off. __________ Fragmenting Plants Ferns Liverworts Mosses Succulents Willows and poplars

Asexual Reproduction Using Fragments Piece of stem or roots from some plants can be cut off and planted. ___________

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Asexual Reproduction Using Special Structures ___________ No union of sex cells In flowering plants, organs include: Rhizomes Tubers Stolons Corms Bulbs

Rhizomes Long, fleshy, …………….. Branch to grow new plants __________

Tubers Enlarged tips of underground rhizomes or stolons __________ Potatoes are tubers Eyes are buds and can grow into new individuals

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Corms Vertical, fleshy, underground stems __________ Secondary cormlets can grow into new baby plants Gladioli have corms

Bulbs Small bit of stem tissue ……………… Undergo period of dormancy Grow into new plants ____________ Onions form bulbs