Module 5.5 Part 6
- Created by: RebeccaSmithySmith
- Created on: 17-12-18 18:18
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- Module 5.5 Plant Hormones
- Plant Hormones
- Differ from animal ormones
- produced from a specific
- produced by unspecialised cells
- vary depending on circumstances
- e.g. flowering or germination
- Differ from animal ormones
- Phototropic mechanism
- Coordinate by the hormone IAA
- type of auxin
- synthesised in meristem and passed down the stem
- switches genes on/off
- stimulates extension growth
- stimulates proteins in cell wall aka expansins
- (expansins make cell walls more flexible)
- stimulates proteins in cell wall aka expansins
- Coordinate by the hormone IAA
- Geotropism in shoots
- negative tropism in plant stems
- auxins accumulate on the lower side
- e.g. roots grow down
- Apical Dominance
- inhibition of lateral buds by chemicals produced by the optical bud
- auxin's growing at the apex of plants stems causes the stem to grow upwards but also inhibits growth of lateral buds (side buds)
- once the apex is remove lateral buds grow
- cytokines promote lateral bud growth only if tip is removed
- inhibition of lateral buds by chemicals produced by the optical bud
- Gibberellins
- plant hormones involved in growth
- produced in young leaves/seeds/root tips
- stimulates germination, stem growth and flowering
- stimulates cell elongation and promotes cell division
- works synergistically with auxin's
- synergism
- the interaction or cooperation of two or more organisations to produce a combined effect greater than the sum of their separate effects
- plant hormones involved in growth
- hormones and leaf loss
- Deciduous
- plants lose leaves when very hot or very dry
- reduced water loss
- even in winter when water might be frozen
- no photosynthesis
- plants lose leaves when very hot or very dry
- leaf loss is controlled by hormones
- abscission layer (bottom of leaves/stalks develop)
- layer of parenchyma cells within walls
- ethene breaks down cell walls in abscission layers
- leaver fall
- abscission
- the shedding of an old or mature organ froma plant
- abscission layer (bottom of leaves/stalks develop)
- as leafs get older, conc. of auxins decreases
- allows for leaf loss in response to ethene
- Deciduous
- Hormones and stomatal closure
- Abscisic Acid (ABA)
- plant hormone that controls stomatal closure
- produced in roots in response to a decrease in soil water potential
- translocated to leaves
- Guard cells lose water and become less turgid through the following steps
- 1.
- ABA binds to receptors on the cell surface of guard ells (causes a cascade of reaction)
- 2.
- Ca2+ channels open, influx of Ca2+ info guard cells (ph of cytoplasm is raised)
- 3.
- causes k+, NO-3 and CL- ions to leave the cell
- 4.
- water potential of the cell increases
- 5.
- water removed from guard cells by osmosis
- 5.
- water potential of the cell increases
- 4.
- causes k+, NO-3 and CL- ions to leave the cell
- 3.
- Ca2+ channels open, influx of Ca2+ info guard cells (ph of cytoplasm is raised)
- 2.
- ABA binds to receptors on the cell surface of guard ells (causes a cascade of reaction)
- 1.
- Abscisic Acid (ABA)
- Plant Hormones
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