a growth of a plant shoot towards the light
b growth of a plant shoot away from gravity
c plant hormone responsible for stomatal closure d
region responsible for leaf-folding in Mimosa pudica that acts like a joint
e chemicals produced by a plant which acts rather like a pheromone between themselves and other organisms
Volatile organic compounds (VOCs)
3 a Plant responses to environmental changes are co-ordinated by plant growth substances (plant hormones). Explain why plants need to be able to respond to their environment.
To cope with changing conditions/AW Avoid abiotic stress To maximise photosynthesis OR To obtain more, light/water/minerals ORA Avoid, herbivory/grazing To ensure, germination in suitable conditions/pollination/seed set/seed dispersal
c State two commercial uses of plant growth substances.
Seedless, fruits/grapes Weedkillers Rooting powder/to grow cuttings/used in tissue culture Control fruit ripening Controls fruit drop Restrict hedge growth Preserve, cut flowers/green vegetables Specific example of improved fruit quality Producing malt/in brewing
4 With reference to the action of plant hormones, outline how:
a cress seedling growth is affected by overcrowding
Two from: Auxin/IAA (Positive) phototropism Plants/shoots, bend towards light Etiolation/plants grow taller
4 With reference to the action of plant hormones, outline how: b growth of a low hawthorn hedge is affected by grazing by goats
Less auxin/auxin production stopped Apical dominance, stopped/removed Side shoots grow/lateral buds develop/ORA Hedge becomes more bushy
4 With reference to the action of plant hormones, outline how c asparagus growth is affected by covering the young shoots with an upturned box to exclude light.
Auxin/IAA Not destroyed by light/more present in dark Moves down from shoot tip Cell elongation/asparagus grows taller Chloroplasts don’t develop/asparagus is paler
5 A student is provided with two bottles labelled P and Q. One contains a solution of 1% auxin and one contains a solution of 1% gibberellin. Describe how the student could determine experimentally which bottle contains auxin and which contains gibberellin.
§ apply solutions separately · to cut stem tips · to agar block placed on one half of cut stem tip · to stem tip in presence of unidirectional light § run control experiments under same conditions but with no chemical applied
§ treat large number of seedlings or coleoptiles (minimum 10 per treatment) § independent variables are P and Q (and no treatment
) § dependent variable is measurement of, plant height/number of side-shoots/curvature of stem
§ control variables in plant material listed for example, same age/height/mass/genotype
§ control variables in environment listed for example, same soil type /fertiliser/watering regime/light intensity/light direction/light wavelength
§ auxin causes curving of, stem/coleoptiles, towards light in unidirectional light
§ auxin causes curving of, stem/coleoptile, when applied to one side of stem only
§ auxin causes fewer lateral buds to develop (than control)
§ gibberellin causes straight growth of, stem/coleoptile
§ gibberellin causes greater growth in, height/length, of, stem/coleoptiles (than control or auxin)
§ gibberellin causes lateral buds to develop as in control