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Vegetative Plant Development

Chapter 36

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Angiosperm Embryo Development

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Establishing Three Tissue Systems

• Protoderm will become dermal tissue– protects plant from desiccation

• Ground meristem will form ground tissue– function in food and water storage

• Procambium will form vascular tissue– perform water and nutrient transport

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Establishing Three Tissue Systems

• Root and shoot formation– established during globular stage of

development formation of each controlled

independently• Morphogenesis

– globular stage gives rise to heart-shaped embryo with cotyledons produced by embryonic cells

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Establishing Three Tissue Systems

• Food storage– starch, lipids, and proteins produced

throughout embryogenesis sporophyte transfers nutrients via

suspensor in angiosperms

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How Seeds Form

• Protective seed coat forms from outer layers of ovule cells

– embryo either surrounded by nutritive tissues, or amassed food in cotyledons

– seed resistant to drought and other unfavorable conditions

vehicle for dispersal

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How Seeds Form

• Adaptive importance of seeds– maintain dormancy until better conditions

arise– afford maximum protection to young plant

at most vulnerable developmental stage– contain adequate food supply until

photosynthetic food supply available– adapted for dispersal

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How Seeds Form

• Specific germination triggers– exposure to heat or fire– leaching inhibitory chemicals from seed

coats– passage through animal intestines

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How Fruits Form• Fruits are mature ovaries.

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How Fruits Form

• Dispersal of fruits– vertebrate digestive tracts

bright colors– animal coats

hooked spines– wind

wings– water

buoyant

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Mechanisms of Germination

• Germination begins when a seed absorbs water and resumes metabolism.

– may fail to germinate without additional environmental signals

stratified - held at low temperatures

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Mechanisms of Germination

• Utilization of reserves– Germination and early seedling growth

require the utilization of metabolic reserves stored in starch grains of amyloplasts.

cereal cotyledons modified into scutellum– mediated by gibberellic acid and abscisic

acid

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Summary

• Establishing the Root-Shoot Axis• Establishing Three Tissue Systems• How Seeds Form• How Fruits Form• Mechanisms of Germination

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