Horticultural practices — A/L Biology

How do I practise Horticultural practices?

1 question with a worked solution

1. In plant tissue micropropagation, what phytohormone concentration ratio in the sterile nutrient culture medium is applied to stimulate the induction and development of adventitious roots from an undifferentiated callus?
   1. A) High gibberellin to low abscisic acid ratio
   2. B) High cytokinin to low auxin ratio
   3. C) High auxin to low cytokinin ratio
   4. D) High ethylene to low brassinosteroid ratio
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   Correct answer: C) High auxin to low cytokinin ratio

   Skoog and Miller demonstrated that organogenesis in plant tissue culture is governed by the auxin-to-cytokinin ratio. A high auxin to cytokinin ratio (e.g., elevated NAA or IBA relative to BAP/kinetin) induces root differentiation, while a high cytokinin to auxin ratio induces shoot proliferation.

   Show worked solution

   Step 1: Review Skoog and Miller's hormonal balance theory: - Balanced Auxin = Cytokinin -> undifferentiated callus proliferation. - High Cytokinin : Low Auxin -> shoot bud differentiation. - High Auxin : Low Cytokinin -> root induction (rhizogenesis). Answer: High auxin to low cytokinin ratio.
   Modelled on: the A/L Biology examination pattern

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Where does Horticultural practices fit in the syllabus?

Year 2 · Term 3