UT Arlington BIOL BIOL 3427 - ch23 Angiosperms (15 pages)

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ch23 Angiosperms



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ch23 Angiosperms

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Pages:
15
School:
University of Texas at Arlington
Course:
Biol Biol 3427 - Plant Science
Plant Science Documents

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Chapter 23 SEED PLANTS ANGIOSPERMS All flowering plants are classified in a single Division Magnoliophyta Angiosperms are commonly known as flowering plants This division contains the greatest number of living species about 257 000 They are characterized by producing flowers a synapomorphy that unifies them First appeared in the Cretaceous about 130 million years ago The angiosperms have developed numerous methods of interaction with animals that are beneficial to both They have developed many antiherbivore compounds that defend them against plant eating animals and parasites CHARACTERISTICS OF ANGIOSPERMS Woody or herbaceous Presence of vessels Axial parenchyma parenchyma cells mixed with vessels and tracheids Produce flowers Pollinated by wind or animals Double fertilization egg sperm embryo and 2 polar nuclei sperm endosperm Seeds enclosed in a fruit EVOLUTION OF THE FLOWER Angiosperm stamens and carpels developed from the gymnosperm sporophylls Gymnosperm sporophylls are flat and spirally arranged and microsporophylls never occur with megasporophylls Flowering plants with flat spirally arranged flower parts are thought to be most ancient Basal angiosperms have flat stamens without distinct filament and anther portions arranged in spirals and their sporogenous tissues microspore mother cells form relatively large prominent internal masses Amborella Nymphaeales Austrobaileyales and Magnoliales In most angiosperm carpels the edges of sporophyll grow shut against one another sometimes leaving a suture sometimes not These are called closed carpels Closed carpels develop into fruits that enclose the embryos as they develop into seeds Carpels in the basal angiosperms are leaf like resembling young leaves whose blades have not yet opened Basal angiosperms lack stigma and style instead the ovary edges have rows of secretory hairs that secrete a thick liquid that both seals the seam and functions as a stigmatic surface The stigmatic surface acts as a selector of pollen



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