Transcript PLANT DIVERSITY II

Plant Reproduction and Plant
Diversity II
Chapter 30/38
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• Seed plants - vascular plants that
produce seeds.
• 3 adaptations that seed plants
have:
• 1Gametophyte more reduced.
• 2Seed evolved.
• 3Pollen evolved.
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• Gametophytes of seed plants
almost invisible.
• Gametophytes still exist - plants
can destroy themselves at this
stage if there something wrong
with plant.
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http://www.palaeos.com/Plants/Images/PhyscomitrellaRhizoids.jpg
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• Seed - sporophyte embryo
packaged with food supply within
protective coat.
• Seed plants produce 2 different
types of sporangia - produce 2
different types of spores:
megaspores (female gametophyte)
and microspores.
• Gametophytes stay in sporophyte as
it develops.
http://botit.botany.wisc.edu/images/130/Early_development/Bean/bean_seed_2_MC.low.jpg
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• Ovule - integuments (part
protective covering), megaspore,
and megasporangium.
• Female gametophyte develops
inside megaspore; produces 1 + egg
cells.
• Fertilized egg develops into
sporophyte embryo.
• Whole ovule develops into seed.
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• Microspores (pollen) – light, carried
through air.
• Pollen will create pollen tube - allow
sperm to travel down into female
gametophyte.
• 2 groups of seed plants: gymnosperms
and angiosperms.
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Gymnosperms
• 4 phyla of gymnosperms still around.
• Phylum Ginkgophyta contains only Ginkgo
biloba.
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• Phylum Cycadophyta - cycads - look like
palm trees.
• Phylum Gnetophyta - 3 different types
of plants (ephedra)
• Phylum Coniferophyta - largest phyla conifers - from reproductive structure,
cone.
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Conifers
• Conifers are evergreen - keep leaves all
year long.
• Needles help in dry conditions.
• Conifers include pines, firs, spruces,
larches, yews, junipers, cedars,
cypresses, and redwoods.
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Life cycle of gymnosperms
• Conifers - heterosporous (develop male
and female gametophytes)
• Produce pollen cones and ovule cones.
• During pollination, pollen falls on ovule.
• Creates pollen tube that digests
through megaspore.
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• Megaspore, now fertilized, goes through
meiosis to produce 4 haploid cells.
• 1 cell turns into female gametophyte,
others (archegonia) will develop within
gametophyte.
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Angiosperms
• Angiosperms - flowering plants produce flowers, fruit.
• Phylum Anthophyta - all angiosperms.
• Divided into 2 groups: monocots and
dicots.
• Monocots - leaves with parallel veins,
dicots have netlike venation.
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• Angiosperms - long tracheids - help
transport water, support plant.
• Flower specialized for reproduction.
• Most angiosperms rely on pollination
through animals; grasses - random
chance.
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• Flower - specialized shoot - 4
circles of modified leaves: sepals,
petals, stamens, and carpals.
• Sepals - base of flower - modified
leaves that enclose flower before it
opens.
• Petals lie inside ring of sepals usually colorful in animal pollinated
plants.
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• Male organ - stamen - thin, stalk-like
filament with sac at top.
• Anther - produces haploid spores that
develop into pollen grains.
• Female organ - pistil - contains 3 parts:
stigma, style, ovary.
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• Stigma - sticky top part of flower
which extends beyond flower,
catches pollen.
• Style connects stigma to ovary at
base of pistil which allows sperm to
reach ovules.
• Ovary - enlarged area at base of
pistil - contains one or more ovules.
• Entire structure - carpal.
• Ovule contains egg nucleus.
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• Fruit - mature ovary.
• As seeds develop from ovules after
fertilization - wall of ovary thickens
to form fruit.
• Fruit helps protect seeds while
they disperse.
• Some fruits, dandelion, modified to
catch wind.
• Burrs that stick to animals - fruits.
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• Fruit develops after pollination
triggers hormonal changes - cause
ovarian growth.
• Wall of ovary becomes pericarp
(thickened wall of fruit)
• If flower not pollinated - fruit will
not develop.
• 3 different types of fruits.
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• Simple fruits come from single
ovary (cherries)
• Aggregate fruit (blackberry) single flower with several carpals.
• Multiple fruit (pineapple) develops
tightly clustered group of flowers.
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• Ovules - contain female
gametophyte, embryo sac.
• Angiosperm life cycle starts with
mature flower on sporophyte plant
and ends with germinating seed.
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http://www.lclark.edu/~seavey/bio210/flower_dwg_ovules_pjt.gif
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• Anthers of flower produce
microspores that form male
gametophytes (pollen).
• Ovules produce megaspores that
form female gametophytes (embryo
sacs).
• After its release from anther,
pollen carried to sticky stigma of
carpal.
• Plants can self-pollinate; crosspollination better.
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http://utc.usu.edu/factsheets/CarexFSF/CIG/rhexia_anthers4_lg.jpg
• Pollen grain begins growing from
stigma toward ovary.
• Discharges 2 sperm cells into
female gametophyte.
• 1 sperm fuses with egg nucleus to
form diploid zygote.
• Develops into embryo.
• Embryo has rudimentary root; one
(in monocots) or two seed leaves (in
dicots), cotyledons.
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http://biofinity.org/images/Pollen%20Grain%20Micrograph.jpg
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• Other sperm nucleus fuses with 2
polar bodies to form endosperm,
(triploid or 3n) in monocots.
• Dicots - nutrition goes directly to
cotyledons.
• As ovules develop into seeds, ovary
develops into fruit.
• Conditions favorable - germination
occurs (seed coat ruptures, embryo
emerges as seedling)
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http://www.rbgsyd.nsw.gov.au/__data/assets/image/0017/81026/Seed_germination_620.JPG
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• Seedling uses food stored in either
endosperm (monocot) or cotyledon
(dicot) to start growth.
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The fruit
• Ovary of flower develops into fruit,
protects enclosed seeds, aids in
dispersal by wind or animals.
• Wall of ovary becomes pericarp,
(thickened wall of fruit)
• Apples - fleshy from swollen
receptacles.
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• As seed develops - enters dormancy
- allows it to survive until conditions
favorable.
• 1st organ to emerge from
germinating seed - radicle,
embryonic root.
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Asexual reproduction
• Plants can clone - vegetative
reproduction.
• Fragmentation - parent plant
separates into parts - reform whole
plants.
• Scientists use this process to clone
plants used for novelty.
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Co-evolution
• Certain animals only eat certain
plants - forced evolution of one
another.
• Plants evolved special fragrances forces evolution of specific animals
to pollinate these plants.
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Plants and human welfare
• All fruit and vegetable crops angiosperms.
• Corn, rice, wheat, - grass fruits.
• Use plants for medicinal purposes;
more than 25% of our prescriptions
come from plants.
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