Patterns of Reproduction in Plants

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Alternate Generations of Plants Plant life cycle –Two multicellular generations that alternate –One phase includes sexual reproduction

Plant Life Cycles Diploid –Usual complement of chromosome pairs –Includes zygote & sporophyte Haploid –One set of chromosomes only –Includes spores, gametophyte, egg, & sperm

Gametophytes Haploid Haploid spores form gametophyte Form gametes by mitosis

Gamete Formation Eggs formed in archegonia Sperm produced in antheridium Fuse to form zygote

Sporophyte Zygote undergoes mitosis Multicellular sporophyte undergoes meiosis Spores often in cases called sporangia

One Generation Dominates Gametophyte in nonvascular plants –Mosses –Liverworts & hornwort Sporophyte in vascular plants –Ferns –Conifers –Flowering plants

Nonvascular Plants Three phyla –Bryophyta – mosses –Hepatophyta – liverworts –Anthocerophyta – hornwort Gametophyte nutritionally independent Sporophyte grows out of gametophyte

Vascular Plants Seedless vascular plants –Whisk ferns –Club mosses –Horsetails –Ferns Plants with naked seeds –Conifers –Cycads –Ginkos Protected seeds –Angiosperms

Seedless Vascular Plants Seeds contain sporophyte embryos & food Seedless plants compensate for no seed by being tied to favorable habitat Sporophyte is dominant stage

Moss Life cycle

Gymnosperms Exposed (naked) seeds Sporophyte generation dominates Includes conifers, cycads & ginkos

Pine Life Cycle

Angiosperms Protected seeds Flowering plants Largest number of plants

Flowers Organ for sexual reproduction Sepals = outer modified leaves Petals attract pollinators Male stamen Female pistil

Angiosperm Life Cycle

Pollination Method to combine egg & sperm Wind pollination –Gymnosperms –Some angiosperms like grasses

Pollination Insect & animal pollination –Pollen carried from one flower to another –Common in many angiosperms Some are self pollinated

Seed Development Zygote is plant embryo Endosperm –From other sperm nuclei –Feeds embryo Embryo develops cotyledons (seed leaves) –Monocot = single cotyledon –Dicot = double cotyledon

Fruit Mature ovary –Seeds, tissues, and coverings Fruits may allow for animal dispersal

Seed Dispersal Methods Animals, wind, & water

Germination Begins when seed takes up water Initially uses stored food of seed Begins to sprout

Monocots Vs. Dicots Differ in recognizable features Dicots – food stored in cotyledons Monocots – food stored in endosperm

Seedling Development Radicle –First portion to emerge –Anchors seedling Epicotyl –Portion of shoot above cotyledon

Seedling Development Coleoptile –Sheath protecting new leaves Hypocotyl –Shoot below cotyledens

Vegetative Propogation Asexual reproduction New plant develops from portion of parent –Rhizomes = underground stems –Stolons = above ground stems

Vegetative Propogation Leaves can produce new plants

Cell Culture of Plants Plant production from a single cell Produces genetic clones