Chapter 2.1 Natural And Artificial Clones Of Plants Flashcards
When plants produce runners are the reproducing sexually or asexually?
Asexually
What is a clone
A clone is an exact genetic copy of an organism. It can e used to describe genes, cells or whole organisms which carry the same genetic material because they are derived from the same piece of DNA.
Advantages of plants reproducing asexually
It is quick, allowing organisms to reproduce rapidly and so take advantage of resources in their environment.
It can also be completed where sexual reproduction fails or is not possible.
All offspring have the same genetic information which enables them to survive in their environment.
Disadvantages of plants producing asexually
It does not produce any genetic variation, so any genetic parental weaknesses will be passed on, and all members of the species will be susceptible to the same selection pressures.
Likewise, with no genetic variation, this means the adaptations are reduced.
What is natural vegetative propagation?
Vegetative propagation refers to the production of structures in an organism that can grow into new individual organisms. These offspring are clones of the parent as they have the same genetic information.
Natural vegetative propagation of plants can come in 3 forms. What are they & a description.
1) root suckers- grow from meristem tissue in the trunk close to the ground where the least damage is likely to have occurred. Plant species have have adapted to reproduce asexually using this method following damage to the parent plant, allowing species as a whole to survive catastrophes such as diseases.
2) runners - small shoots which run along the ground and cause buds to grow which develop roots.
3) tubers - specialised underground stems which become swollen full if nutrient molecules from which new plants can grow. Potatoes grow this way.
Artificial vegetative propagation
Farmers have been able to use artificial vegetative propagation methods to allow valuable plants tore produce asexually, keeping their successful traits.
2 main methods of artificial vegetative propagation?
1) cuttings - a section of stem is cut between leaf joints (nodes) and the cut end of the stem is then treated with plant hormones to encourage root growth, and planted - the cutting forms a new plant which is a clone if the original parent plant - this allows large numbers if genetic clones to be produced quickly.
2) grafting - a shoot section of a woody plant, such as a fruit tree or a rosebush, is joined to an already growing root and stem (rootstock) and the graft will grow., being genetically identical to the parent plant, despite the rootstock being genetically different.
True or false. Taking cuttings or grafts of plants produce large numbers of genetically identical offspring with ease
False
What is a more modern technique of artificial vegetative propagation?
Tissue culture
Advantages of tissue culture.
Produce huge numbers of genetically identical daughter plants from a small piece of starting plant material.
Useful in generating large stocks of beneficial and advantageous plants, such as those which are immune to a particular disease.
What is the most common technique of tissue culture in plants
Micropropagation
Outline the process of micropropagation
1) a small piece of tissue, called an explant, is taken from the plant to be cloned, usually from the shoot tip.
2) the explant is placed inside a nutrient growth medium.
3) cells in the tissue divide, but do not differentiate, instead forming a large mass of undifferentiated cells, called a callus.
4) after a few weeks, single callus cells can be removed from the mass and placed on a growing medium containing plant hormones that encourage shoot growth.
5) after a further few weeks, the growing shoots are transferred onto a different growth medium containing different hormone concentrations, that stimulate root growth.
6) the growing plants will then be transferred to a greenhouse to be acclimatised and grown before they are planted.
Evaluation of artificial vegetative propagation
Using methods such as callus tissue culture farmers know what the plant outcomes will be and can retain favourable characteristics of plants. Also from a commercial side the farming costs are decreased as the entire crop will be ready at the same time.
Micropropagation is much faster than selective breeding because huge numbers of genetically identical plants can be generated from a single variable plant.
Disadvantages:
Genetic uniformity means that all individuals are equally susceptible to the same diseases, pests or environmental conditions.
Have to carefully monitor the distance between farms harvesting genetically identical crops to limit the effects of a new pathogen to the farm and wiping out all plants.
