6.4 Flashcards
Define a clone.
Genetically identical organisms or cells.
Define vegetative propagation.
Reproduction from vegetative parts of plant - usually an overwintering organ.
Advantages of natural cloning?
- If environment has conditions of growth good for parent they will also be good for the offspring.
- Relatively quick allowing organism to take advantage of conditions
- Only requires one parent
Disadvantages of natural cloning?
- Offspring may become overcrowded
- No genetic diversity (unless mutation occurs)
- No selection can occur as result of no variation
- Environment changes affects all organisms
What are horizontal stems which grow on the surface of the ground called?
Stolen or runners.
What are horizontal stems which grow underground called?
Rhizomes - these can be overwintering organs where new stems can grow from in spring.
What are stems that grow from the roots of a plant called?
Suckers - they form ether at the base of an older root or could be some distance away. In all cases horizontal branch dies leaving stem as separate individual.
Describe Bulbs.
Bulbs are an overwintering mechanism which consists of an underground stem that grow fleshy leaf bases. It also has an apical bud. Often it has more then one and each grow into a new plant.
Describe Corms.
Solid with an underground stems that grows scaly leaves and buds. Remain underground throughout winter and in spring buds grow to produce more new plants.
How do leaves allow natural cloning to occur?
In Kalanchoe plants leaves grow on the margins which drops off and develops its own root.
What are tubers?
Underground stem (potatoes)
What is micropropagation?
Growing a large number of new plants from meristem tissue from a sample plant.
What is tissue culture?
Growing certain tissues, organs or plants from tissue taken from sample plant.
How to create a natural clone of a plant?
1) Make a cutting between two leaf joints (nodes)
2) Place cut end of stem into moist soil
3) New roots will grow from tissue in soil usually from the node.
4) Cutting can be dipped in rooting hormone to stimulate root growth
How is tissue culture carried out?
- Take sample of tissue
- Place onto growth medium in sterile conditions
- Apply certain growth substances at certain times to encourage differentiation of growing cells.
Explain the step of propagation?
1) Plant material selected and cut into pieces, called an explant. Meristem is good choice as free from viral infection.
2) Explants are sterilised using dilute bleach or alcohol to kill bacteria and fungi as conditions supplied later will allow them to grow.
3) Explants are placed onto sterile growth medium containing nutrients (amino acids, glucose & phosphate). Growth medium has high concentration of auxin and cytokinin which stimulates cell division (mitosis) into callus, which is a mass of undifferentiated totipotent cells.
4) Once callus formed its divided to form smaller clumps of undifferentiated cells
5) Small clumps of cells stimulated to grow, divide and differentiate into plant tissue by being placed into different growth mediums.
100: 1 = Roots
4: 1 = Shoots
6) Once plantlet’s formed they are taken to greenhouse to be grown in compost or soil.
What are advantages of artificial cloning?
- Faster then growing from seed
- Meristem tissue use ensures free from viral infection
- Phenotype in offspring uniform making easier to grow and harvest
- Possible with plants that can not sexually reproduce
- Genetically identical therefore desirable characteristics maintained.
What are disadvantages of artificial cloning?
- Labour intensive
- No genetic variation
- Can fail due to microbial contamination
- All genetically identical therefore all susceptible to same disease/pests.
What is embryo twinning?
Splitting of an embryo to create genetically identical embryos
What is enucleation?
Removal of cell nucleus
What is Somatic cell nuclear transfer?
A technique that involves transferring nucleus from somatic cell to egg cell
Explain steps of embryo splitting?
1) Zygote created by IVF
2) Zygote allowed to divide by mitosis into small ball of cells
3) They are then divided and then allowed to continue growing
4) Each mass of cells placed in uterus of surrogate mothers