pattern of reproduction in plant
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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