Question: Explain Variegation in Ivy (viii): causes and possible changes
On very rare occasions a green plant develops a yellow or variegated shoot. These mutations are called a sport (a shoot with a different habit or leaf shape is also called a sport). Consecutive changes, leaf colour wise, are caused by chimeral rearrangement, back mutation or mitotic recombination.
As stated before a chimera originates from a mutation, usually as a sport. Chimeral variegation is not inheritable because only 1 layer (L3 for Hedera helix and other species) is responsible for contributing egg cells or pollen. Another sport originates from a mutation indirectly changing the development of chloroplasts. This feature is inheritable because it is caused by a nuclear mutation.
When a chimeral rearrangement occurs cells are exchanged between 2 layers of a chimera. When layers exchange cells a green or yellow sport may develop. A shift of cells from L2 to L1 may have no visible effect because L1 doesn't contribute cells that develop chloroplasts.
A back mutation is a mutation where a cultivar reverts to the wild type. Back mutation is as rare as a 'normal' mutation so a sport on a cultivar is usually caused by a, also rare, chimeral rearrangement or mitotic recombination, depending on the mutation.
Mitotic recombination is the exchange of part of a chromosome due to an error during cell division (mitosis). To understand mitotic recombination you need to know, to some extend, what stages a cell goes through during mitosis. In my next post I'll cover mitosis.
Source: Variegated trees & shrubs, Ronald Houtman, 2004, Timber Press
As stated before a chimera originates from a mutation, usually as a sport. Chimeral variegation is not inheritable because only 1 layer (L3 for Hedera helix and other species) is responsible for contributing egg cells or pollen. Another sport originates from a mutation indirectly changing the development of chloroplasts. This feature is inheritable because it is caused by a nuclear mutation.
When a chimeral rearrangement occurs cells are exchanged between 2 layers of a chimera. When layers exchange cells a green or yellow sport may develop. A shift of cells from L2 to L1 may have no visible effect because L1 doesn't contribute cells that develop chloroplasts.
A back mutation is a mutation where a cultivar reverts to the wild type. Back mutation is as rare as a 'normal' mutation so a sport on a cultivar is usually caused by a, also rare, chimeral rearrangement or mitotic recombination, depending on the mutation.
Mitotic recombination is the exchange of part of a chromosome due to an error during cell division (mitosis). To understand mitotic recombination you need to know, to some extend, what stages a cell goes through during mitosis. In my next post I'll cover mitosis.
Source: Variegated trees & shrubs, Ronald Houtman, 2004, Timber Press
posted by Me, Myself and Ivy at 9:48 AM
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