1041SCG Lecture Notes - Lecture 12: Seta, Plant Reproductive Morphology, Hypersensitive Response
19 Jun 2018
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1041SCG Biology Systems Notes
Weeks 12
12.1 Plant Growth and Development
Plant differentiation from animals
Meristems: permeant collection of stem cells that allow growth throughout their lifetimes
Post-embryonic organ formation: plants can initiate development of new organs throughout
their lifetime
Differential growth: resources can be allocated for beneficial growth patterns e.g.. more
leaves to harvest sunlight or more roots to obtain water/nutrients
Development in response to environment:
Environmental cues (daylength)
Receptors to sense environmental cues (photoreceptors)
Hormones (chemical signals)
Genes (contained in plants genome)
Dormancy: development of embryo has stopped
Dormancy maintained by:
Exclusion of water or oxygen by impermeable seed coat
Mechanical restraint of embryo by tough seed coat
Chemical inhibition of germination
Thermodormancy: some seeds require a period of high or low temperature to germinate!
Advantages of dormancy:
Ensures survival during unfavourable conditions
Results on germination when conditions are favourable
Helps seeds survive long-distance dispersal, allowing plants to colonise new territory
Seed dormancy broken by:
Passage through an animal’s digestive system may damage seed coat
Burial in soil
Germination inhibitors may be washed away with rain
Germination: seeds begin to grow or sprout
Compete when radicle (embryonic root) emerges
Inhibition: seeds take up water if seed coat is permeable
Early shoot development:
Monocots: growing shoot is protected by sheath of cells
Eudicots: growing shoot protected by cotyledons
Influences on plant growth:
Hormones: chemical signals that cat at a very low concentration at sites often far away
from where they are produced
Photorecepter: proteins with associated pigments that absorb light
First plant hormones identified were gibberellins and auxin
Gibberellins: stem elongation, fruit growth, seed germination
Auxin: in context of phototropism, stems bend toward light
Made in the shoot apex and diffuses down shoot in one direction
Auxin can also be transported laterally in a stem, also have role in gravitropism
Root initiation: shoot cuttings of many species will develop roots if cut surface is dipped into
an auxin solution
Help maintain apical dominance
find more resources at oneclass.com
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Document Summary
Meristems: permeant collection of stem cells that allow growth throughout their lifetimes. Post-embryonic organ formation: plants can initiate development of new organs throughout their lifetime. Differential growth: resources can be allocated for bene cial growth patterns e. g more leaves to harvest sunlight or more roots to obtain water/nutrients. Exclusion of water or oxygen by impermeable seed coat. Mechanical restraint of embryo by tough seed coat. Thermodormancy: some seeds require a period of high or low temperature to germinate. Helps seeds survive long-distance dispersal, allowing plants to colonise new territory. Passage through an animal"s digestive system may damage seed coat. Germination inhibitors may be washed away with rain. Inhibition: seeds take up water if seed coat is permeable. Monocots: growing shoot is protected by sheath of cells. Hormones: chemical signals that cat at a very low concentration at sites often far away from where they are produced. Photorecepter: proteins with associated pigments that absorb light.
