Unformatted text preview: duced in root tips, transported via xylem. Action of Cytokinins
Action Promote cell division.
Delay senescence of leaves.
Can release lateral buds from apical dominance.
Promote shoot formation in tissue cultures. Cytokinin/ Auxin Interactions In Tissue
Cultures (p. 646-647; 609-610)
609-610 Auxin alone: rapid cell expansion, giant
Cytokinin alone: minimal effect
Equal cytokinin + auxin: rapid cell divisionformation of many small undifferentiated
Cytokinin + high auxin: root formation.
High cytokinin + auxin: bud, shoot
formation. Ethylene (p. 647; 611)
Ethylene Simple hydrocarbon: C2H4.
Leaking gas from 19th C gaslights caused defoliation of
Produced in many tissues, as response to stress or
during senescence/ ripening.
Moves via simple diffusion.
Commercial uses—ripen green-picked tomatoes, etc. Action of Ethylene
Action Fruit ripening.
Leaf & flower senescence.
Usually Inhibits cell expansion.
Triggers rapid stem elongation in aquatic species (rice,
water lilies) during flooding.
Causes air spaces to develop in submerged tissues of
flooded ABA (Abscisic Acid) p. 649; 612
612 Paul Wareing (1949) isolated a powerful growth
inhibitor from dormant buds.
Despite name, no role in abscission (abbreviation
ABA is preferred).
• Prevents seed germination.
• Keeps buds dormant.
• Root to shoot signaling during stress.
• Triggers stomata to close
Transported via phloem & xylem. Action of Abscisic Acid
Action Prevents seed germination:
• Mutant corn grains germinate
Induces stomatal closu...
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- Spring '14
- Botany, Cytokinins, Apical dominance