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STARTER – Topic 9 MCQS

STARTER – Topic 9 MCQS. 1. C 2. C 3. B 4. A 5. C 6. B 7. B. 8. C 9. B 10. C 11. D 12. C 13. C. Learning Objectives. Outline the metabolic processes during germination of a starchy seed.

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STARTER – Topic 9 MCQS

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  1. STARTER– Topic 9 MCQS • 1. C • 2. C • 3. B • 4. A • 5. C • 6. B • 7. B • 8. C • 9. B • 10. C • 11. D • 12. C • 13. C

  2. LearningObjectives • Outlinethe metabolic processes during germination of a starchy seed. • Explainhow flowering is controlled in long-day and short-day plants, including the role of phytochrome.

  3. Definitions Phytochrome • protein pigment held in plant leaves • has two distinct but interchangeable forms: • PR (or P660) and PFR (P735) Photoperiod • the number of daylight hours in a 24hr cycle • varies with the seasons

  4. Phytochrome and the photoperiod Rapid conversion in daylight PR PFR Slow dark reconversion

  5. Phytochrome and the photoperiod So the ratio of PR to PFR at dawn gives a measure of the changing seasons… Rapid conversion in daylight PR PFR Slow dark reconversion

  6. Phytochrome and the photoperiod If PR:PFR at dawn is falling, the days are getting… …longer meaning that… …summer is coming Rapid conversion in daylight PR PFR Slow dark reconversion

  7. Phytochrome and the photoperiod If PR:PFR at dawn is rising, the days are getting… …shorter meaning that… …winter is coming Rapid conversion in daylight PR PFR Slow dark reconversion

  8. Phytochrome and the photoperiod This means that plants can react to coming seasons and prepare physiologically for them Rapid conversion in daylight PR PFR Slow dark reconversion

  9. Phytochrome and flowering • One clear example of physiological response to the seasons is flowering • Plants need to have flowers mature when insects become abundant to increase chances of pollination • Development of flowers is a slow process and needs to begin long before insects appear

  10. Spinach: a long day species Poinsettia: a short day species Long and short day species • In all plants flowering is brought about by the hormone Florigen • Long day species are those which flower in response to long days (short nights) PFR is the trigger for florigen secretion • Short day species are those which flower in response to short days (long nights) PR is the trigger for florigen secretion • In day neutral species some other trigger (e.g. temperature causes flowering)

  11. Simulating long nights • A brief exposure of plants to pure far red light causes a rapid conversions of PFR to PR Flash of far red light PR PFR This replaces the need for long periods of darkness to stimulate flowering in SDS and has commercial applications

  12. Demo time!

  13. ? • + = flowering, _= no flowering

  14. + = flowering, _= no flowering ?

  15. + = flowering, _= no flowering ?

  16. + = flowering, _= no flowering ?

  17. + = flowering, _= no flowering

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