Plant cloning

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  • Plant Cloning
    • Asexual reproduction:
      • Advantages:
        • Only requires 1 plant so FAST process as no need to find a mate. All offspring have the same genetic information so will be WELL ADAPTED to their environment.
      • Disadvantages:
        • LACK of genetic VARIATION, so cannot evolve or adapt to change. 1 disease may wipe entire population out.
    • Natural vegetative propagation:
      • Tubers e.g. potato, root suckers/basal sprouts e.g. Elm trees, runners e.g. strawberries, bulbs e.g. daffodils.
    • Asexual reproduction in Elm trees:
      • Happens following damage/stress to parent tree. New growth in form of ROOT SUCKERS/ basal sprouts from meristem tissue in trunk close to ground within 2 months. Suckers all round trunk - Clonal patch which in turn put out suckers. Clonal patches - initially still roots connected to a tree.
      • Problems: DUTCH ELM DISEASE. This devastated populations of Elm trees in Europe. Caused by a FUNGAL PATHOGEN spread by the Elm bark beetle. Fungus accidentally introduced from Asia.
    • Ways disease can spread:
      • Roots spread, insects, Tree surgeon contamination.
    • Artificial vegetative propagation:
      • 1. Taking CUTTINGS, 2. GRAFTING - SCION not genetically identical to root. 3. TISSUE CULTURE.
    • Taking cuttings:
      • 1. Take section of stem cut between leaf joints (nodes).
      • 2. Cut end is dipped into rooting powder which contains plant hormones (AUXIN) to encourage growth.
      • 3. Planted where it should start to develop roots and leaves.
    • Tissue culture:
      • 1. The leaf cells explant are taken from meristems in  the shoot tips with sterile forceps.
      • 2. Plant sterilised by dipping intto bleach so no plants will be infected.
      • 3. Section of cells transferred to nutrient agar containing nutrients e.g. potassium, magensium, glucose which assist in plant's growth.
      • 4. Cells are subdivided from callus culture and placed in agar which will stimulate shoot growth through use of hormone e.g. auxin.
      • 5. Plantlets transferred into agar containing root stimulating hormones e.g. cytokinin and auxin where plantlets will differentiate.
        • 6. Plantlets planted into compost/soil/greenhouse in aseptic conditions and grow into larger plants with same genetic information.
    • Micropropagation:
      • Advantages:
        • Quick, produce a large amount, not reliant on environment so done anywhere, genetically identical, disease free,.
          • At same point of growth, useful for rare/endangered species, uniformity makes marketing easier, shipped in large numbers.
      • Disadvantages
        • Time consuming, expensive e.g. to maintain temperature, need lots of space, no genetic variation, requires sterile facilities + trained staff, susceptible to disease.

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