Natural cloning in plants
Natural Cloning
- Asexual reproduction is a form of natural cloning, resulting in genetically identical offspring produced by mitosis.
- A.k.a Vegetative Propagation
- A structure develops from the parent plant, and then becomes independent from the parent
- Usually involves perennating plants where a plant is able to survive a period of annual dormancy.
- Natural plant cloning occurs in...
- Bulbs, such as daffodils; The bulbs of the plant swell with stored food from photosynthesis, buds grow internally and then develop into new shoots the next year.
- Runners, such as spider plants; A lateral stem grows away from the parent plant, and roots develop when the stem touches the ground. The plant then becomes independant once the runner stem dies.
- Rhizomes, such as marram grass; A rhizome (specialised underground horizontal stem) swells with stored food from photosynthesis, before new shoots develop vertically and then become independant.
- Stem Tubers. such as potatoes; The tip of an underground stem becomes swollen with stored food to form a tuber/storage organ. Buds on the storage organ develop into new shoots, becoming independent from the parent organism.
- Natural plant cloning is exploited by farmers and gardeners to produce large quantities of genetically desirable (and identical) plants very cheaply.
- As well as cutting up storage organs, splitting up rhizomes and runners and separating bulbs. cuttings can be taken.
- These cuttings can then be planted straight away, but often rooting hormone is applied.
- This encourages the growth of new roots.
- Propagation from cutting has several advantages over using seeds...
- Quicker
- Guarantees good crop, as the cuttings are genetically identical to the parent so have the same beneficial phenotypes.
- Propagation from cuttings also has some disadvantages...
- As all the plants are identical, environmental change, pests and plant diseases will be able to kill an entire genetically identical population as long as they are able to kill one, as no sister plant will have any tolerance or resistance.
- Many of the world's most important food crops such as bananas, sweet potatoes, coffee and tea are all made by making stem cuttings.
- Sugar cane is also made from stem cuttings, which are then used to to make biofuels as they are one of the world's fastest growing crops - up to 5 metres in 11 months.
- 30cm cuttings are taken, then planted in shallow trenches and covered in soil and left to grow.
- To increase the success rate of natural cloning by propagation of cuttings you should...
- Use a non-flowering stem.
- Make an oblique (diagonal) cut in the stem.
- Use hormone rooting powder.
- Remove all but 2-4 leaves.
- Keep well watered.
- Cover the cutting with a plastic bag for the first few days.
- Bananas are thought to be one of the oldest crops, and also the first to be cloned.
- Wild bananas are full of seeds and inedible, but a mutation meant fruit was produced without fertile seeds.
- These were naturally cloned to propagate sweet, tasty, seedless fruit.
- In the early 20th century, almost all sweet bananas were the Gros Michel variety, and then fungal panama disease wiped them out in most major growing countries as they were all clones so had no genetic resistance.
- Cavendish bananas, although not as tasty as Gros Michel bananas, were resistant so now they are the most common. However as they are also all clones, Black Sigatoka is destroying Cavendish banana plantations.
- New biotechnologies offer the hope of genetically engineered bananas with resistance genes from the original wild fruit, then propagated to restock banana plantations.