Chemical control in plantsEdexcel A-Level Biology B: Flashcards
What these 14 flashcards ask
- Name three plant growth substances.
- How does auxin cause cell elongation?
- What are expansins?
- What is apical dominance?
- Why are auxin and cytokinin described as antagonistic?
- Why does removing the apical bud make a plant bushier?
- Which part of a cereal grain releases gibberellin?
- What does gibberellin do in a germinating cereal grain?
- Why is amylase needed for the embryo to grow?
- In Core Practical 14, what does a clear zone on starch agar show?
- What are the two forms of phytochrome?
- Which form of phytochrome is active?
- How does a short-day plant detect that it is time to flower?
- What is photomorphogenesis?
Exam questions on Chemical control in plants
- A maltster prepares barley for brewing by soaking the grains and letting them germinate. During germination the embryo releases gibberellin, which diffuses to the aleurone layer around the starch-rich endosperm. The aleurone cells then make and release amylase. The maltster stops germination by heating the grains once enough starch has been broken down.Explain how the production of amylase allows the barley embryo to grow.2 marks
- A gardener has three identical single-stemmed saplings of a shrub. On plant X she removes the apical bud. Plant Y is left intact. On plant Z she removes the apical bud and immediately applies a paste containing auxin to the cut surface. After two weeks plant X has produced many lateral shoots, whereas plants Y and Z have produced almost none.Explain why plant X produced many lateral shoots.2 marks
- A student investigates the effect of gibberellic acid on amylase production. She cuts barley grains in half and keeps only the halves without an embryo. She places five halves, cut face down, on each of four starch agar plates containing gibberellic acid at 0, 1, 10 and 100 mg dm⁻³. After 48 hours she removes the grain halves and floods each plate with iodine solution. The mean diameter of the clear zone around the grain halves is 0 mm, 6 mm, 12 mm and 14 mm respectively.Explain the appearance of the plates after they were flooded with iodine solution, including the plate that contained no gibberellic acid.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).