Module 5.5 part 7
- Created by: RebeccaSmithySmith
- Created on: 17-12-18 19:51
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- Module 5.5 controlling plant growth & commercial use of plant hormones
- Effects of Plant hormones
- Cytokinins
- promotes cell division & cell expansion/delay leaf senescence/overcome apical dominance
- Abscisic acid
- inhibit seed germination & growth/stomatal closure during water stress
- Auxins
- promote cell elongation/inhibit growth of lateral shoots (apical dominance)/inhibit leaf abscission
- Gibberellins
- promote seed germination & elongation of stems
- Ethene
- promotes fruit ripening
- Cytokinins
- Role of auxin's in apical dominance
- 1. breaking off the shoots tip (apex) results in growth of lateral branches
- 2. applying auxin paste to the cut end restores apical dominance
- 3. applying a ring of auxin transport inhibitor below the apex removes apical dominance
- ... auxin level in lateral buds increases when the apex is removed
- lateral evidence
- abscisic acid (ABA) inhibits bud growth, lateral buds start to grow when ABA levels drop
- Auxin and ABA are synergistic (promote each others effects)
- cytokinins can override apical dominance if applied directly
- shot apex is normallly the sink for cytokinins from the root, if it is removed they are diverted to the lateral buds
- Do gibberellins cause stem elongation?
- tall peas
- dominant homozygous alleles
- dwarf peas
- recessive homozygous alleles
- tall peas
- how does gibberellin work?
- stimulating cell elongation
- loosening cell walls
- stimulating cell division
- stimulating a cell cycle protein
- causes growth in the internodes
- stimulating cell elongation
- Commercial
- Auxins
- weed killer
- high concentration causes rapid growth
- tissues become sistorted and the damage allows pathogens to entre
- Synthetic auxin's (higher conc. than natural)
- useful in fields of cereals/lawns
- grasses are less sensitive
- weed killers selectivly destroy broad-leaved weeds
- useful in fields of cereals/lawns
- stimulates root growth in cuttings
- commercially available as rooting powders
- inhibits fruit abscission
- e.g. in orchards fruit drops and rots
- Gibberellins
- treats unpollinated flowers
- causes fruit to develop e.g. seedless grapes
- fruits formed without fertilisation are called parthenocarpic fruits
- treats unpollinated flowers
- Ethene
- timulates fruit ripening
- useful in fruits that are liable to damage during transport
- e.g.tomatoes
- useful in fruits that are liable to damage during transport
- fruits picked when unripe and hard
- transported
- artificially ripened in transit or at the destination using ethene
- timulates fruit ripening
- Auxins
- Effects of Plant hormones
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