Flowers

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Flowers
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Basic structure of the angiosperm flower
The fertilization process
Pollen and stigma self-incompatibility
The efficiency of animal pollination
Some basic types of flower
Reproduction and diversity of angiosperms
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Basic structure of the angiosperm flower
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Collective nouns that can cause confusion!
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Evolution of the pistil
Ways in which Angiosperms are different from
Gymnosperms
Angio-Gymno 4 Ovules protected within an enclosed
structure
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about meiosis, mitosis and cytokinesis?
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Life cycle of angiosperms
Fig. 17.12
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The fertilization process in Angiosperms
(Equivalent to Fig 31.10)
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Development of gametophytes
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Ways in which Angiosperms are different from
Gymnosperms
Angio-Gymno 5. Double fertilization to produce
diploid zygote and triploid endosperm nucleus
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What goes on in the endosperm?
The triploid nucleus divides and the endosperm
cell becomes a supercell with many nuclei and a
milky consistency. Cyotkinesis forms membranes
and walls between the nuclei and makes the
endosperm more solid. The developing embryo
uses the nutrients stored in the endosperm, as
does the moncot seedling after germination. In
most dicots, food reserves are moved to the
cotyledons and the endosperm is not present in a
mature seed.
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Somatic cell division involves two successive
steps mitosis and cytokinesis. In mitosis, the
nuclear DNA duplicates and chromosomes segregates
equally between the two daughter nuclei
cytokinesis divides these two nuclei and
cytoplasm, including related cytoplasmic
organelles, into two individual cells.
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Ways in which Angiosperms are different from
Gymnosperms
Angio-Gymno 5. Generally angiosperms have
hermaphrodite flowers and cross pollinate (70)

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how many alleles there are at a locus?
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Pollen and stigma incompatibility
There can be dozens of alleles of the S-gene. If
a pollen grain has an allele that matches an
allele of the stigma upon which it lands, then
the pollen tube fails to grow. What happens when
pollen from plants with three different allele
pairs is crossed with an S1S2 plant? This system
prevents self-fertilization AND fertilization
from close relatives.
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Rye grass incompatibility
Pollen Grain Size and Surface Morphology in a
Perennial Rye Grass Hybrid
Attempts to hybridize between particular
varieties resulted in production of a web-like
substance and incompatibility
Pollen grain on stigma
Stacey Lacoste
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The efficiency of animal pollination
Pollen is up to 30 protein
Nucleus of tube cell
Animal pollination is targeted and so is more
efficient than wind pollination.
Generative cell
Animal pollinated flowers generally produce much
less pollen than wind pollinated flowers.
Pollen is important for animals and many animal
pollinated plants do produce excess pollen.
Lilium pollen
http//www.uri.edu/artsci/bio/plant_anatomy/images
/153.gif
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Some basic types of flower
Separate petals
Magnolia grandiflora
http//www.csdl.tamu.edu/FLORA/gallery4.htm
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Flowers with a tubular corolla
Gentiana algida Rocky Mountain National Park CO
http//www.csdl.tamu.edu/FLORA/gallery4.htm
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A head with many florets
http//www.csdl.tamu.edu/FLORA/gallery4.htm
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Monocotyledons
Flower parts in threes
Narcissus spp.
http//www.csdl.tamu.edu/FLORA/gallery4.htm
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Monoecious, wind pollinated
Oaks, have separate male and female flowers.
The female flower (upper left) consists only of
carpels and a calyx (collection of sepals). The
male flowers are in elongated clusters, called
catkins, and consist only of anthers and a calyx.
Both sexes are found on the same tree, and thus
oaks are monoecious (meaning same house). Some
trees, e.g., poplars and willows are dioecious
(meaning two houses), and there are male and
female trees. Other monoecious genera include
birch, walnut, ash, hickory, and most maples.
http//forest.wisc.edu/forestry415/INDEXFRAMES.HTM
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Reproduction and diversity of angiosperms
Animal pollination is efficient and associated
with the development of the hermaphrodite
reproductive axis
The diversity of flowers represent mechanisms
promoting efficient pollination
Prevention of self-fertilization maintains
genetic variation by promoting cross pollination
Sophistication of the reproductive process
enables a large number of ways reproductive
isolation can occur and so maintains genetic
diversity
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Sections you need to have read
17.10 through 17.14 and 31.9 and 31.10
Courses that deal with this topic
Botany 113 Plant identification and
classification