Chapter 5: Plant Responses Flashcards
Outline three chemical defences in plants
- Alkaloids
- Tannins
- Pheromones
What is abiotic stress? Give two examples
Stress from the abiotic factors in the environment - eg. Drought, day length
How do Pheromones protect the plant from herbivory?
Signalling chemicals that will produce a response in other organisms
How does Auxin work in the shoot of a plant?
- Avoids light
- Promotes cell elongation by activating proteins in the cell walls (expansins) to loosen bonds between cellulose microfibrils
- Shoot grows towards the light
True or False: Plants are negatively phototropic
False
How do plants prevent from freezing?
- Abscisic acid is released which stimulates the cold responses
- Sugars may act as anti-freeze protecting
- Cell sap and cytoplasm decrease their freezing point
Suggest one commercial use of the plant hormone Gibberellins
- To delay ripening
Why do deciduous plants lose their leaves in the winter?
The cold weakens the cell walls so abscission takes place to conserve ATP in the rest of the plant as the leaves require too much ATP
Outline two functions of Abscisic acid in plants
- Stimulates cold protective responses
- Inhibits seed germination
Suggest one commercial use for the plant hormone Cytokinins
- To prevent ripened fruit from aging
How do Alkaloids protect the plant from herbivory?
They can contain nicotine, caffeine and poison
Outline two functions of the plant hormone Ethene
- Fruit ripening
- Promotes production of cellulose which promotes leaf abscission
Suggest and explain one commercial use of the plant hormone Ethene
- Ripen fruit: Ethene promotes fruit ripening and abscission of fruit/leaves
How is the stomata controlled during water stress?
- Roots produce abscisic acid which bind to the guard cells
- Leads to the turgor decreasing and stomata closing
How will root growth be affected if the tip is removed?
Auxin is synthesised in the tip and it inhibits cell elongation in the roots - roots will keep growing
What are two limitations of the investigation were we investigate the effect of auxin on root growth?
- Despite being the same species, plants will have genetic differences eg. sensitivities to auxin
- Evenness of growth can be hard to determine - human error
Outline two functions of Gibberellins in plants
- Stimulates cell division - cell elongation
- Promotes seed germination
What is it known as when shoot grow in the opposite direction of gravity?
Negative geotropism
Outline two functions of the plant hormone Cytokinins
- Promote bud growth
- Side shoot formation
Outline three functions of the plant hormone Auxin
- Stimulates growth in shoots and inhibits growth in roots
- Promotes apical dominance
- Inhibits leaf abscission
Suggest and explain three commercial uses of the plant hormone Auxin
- Selective weed killers: High concentrations cause the plant to grow too quickly, damaging tissues, exposing the plant to pathogens
- Rooting powders: Low concentrations can be used to stimulate growth from cuttings to produce new roots
- Producing seedless fruits
Outline three physical defences in plants
- Thorns
- Spiny leaves
- Stings
How do Tannins protect the plant from herbivory?
Bitter taste
