Patterns of Reproductionin Plants

Patterns of Reproductionin 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