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Flowers 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 Basic structure of the angiosperm flower

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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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Collective nouns that can cause confusion!

Calyx

The outer whorl of a flower made up of sepals that are usually green, and protect the flower in bud.

Carpel

Bears the stigma, and frequently an elongated style, and encloses the ovules (sometimes gynaecium). The megasporophyll of the flower

Corolla

The collective term for the petals of a flower

Ovary

The total of the carpels in a flower is the ovary

Perianth

The floral envelope, it includes the calyx and corolla.

Pistil

Each separate carpel when there are lots of them in the ovary

Stamen

The anther and its supporting filament. The microsporophyll of the flower


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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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The fertilization process in Angiosperms

(Equivalent to Fig 31.10)



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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 and cytokinesis.

Angio-Gymno 5. Generally angiosperms have hermaphrodite flowers and cross pollinate (70%)



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Pollen and stigma incompatibility and cytokinesis.

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 and cytokinesis.

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 and cytokinesis.

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 and cytokinesis.

Separate petals

Magnolia grandiflora

http://www.csdl.tamu.edu/FLORA/gallery4.htm


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Flowers with a tubular corolla and cytokinesis.

Gentiana algida

Rocky Mountain National Park CO

http://www.csdl.tamu.edu/FLORA/gallery4.htm


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A head with many florets and cytokinesis.

http://www.csdl.tamu.edu/FLORA/gallery4.htm


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Monocotyledons and cytokinesis.

Flower parts in threes

Narcissus spp.

http://www.csdl.tamu.edu/FLORA/gallery4.htm


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Monoecious, wind pollinated and cytokinesis.

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 and cytokinesis.

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 and cytokinesis.

17.10 through 17.14 and 31.9 and 31.10

Courses that deal with this topic

Botany 113 Plant identification and classification


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