Strange, no?

This event occurred due to something called a somatic mutation. Such localized changes as seen in this flower are called chimera.

Mutations are spontaneous alterations in genes which can change their expression. They are relatively rare events. Working with plants I generally see one a year. Mutation rates vary with species but estimates for various ones range from 1 in a million to 1 in 10,000.

Generally what happens is something induces a change in the DNA usually when cells are dividing. In the case with somatic mutations these probably happen during mitosis (remember all those phases of cell division in biology like prophase,anaphase etc? sometime in those processes something creates a change in the way the DNA strands reorganize - gene inversions, deletions, crossovers...). This kind of change can result in a localized effect, such as one Alfredo's flower, one branch, a side of a plant or if early enough in development the majority of a plant. Environmental influences, such as temperature, ultraviolet light, chemicals, viruses, or as mentioned above just problems in cell reproduction can induce or contribute to such mutations.

Somatic mutations are not passed on in the next generation. When unique somatic mutations are found they must be maintained by cuttings or cloning propagation. An example of this in horticulture are dwarf Alberta spruces which was a somatic mutation induced by a pathogen called "witches brooming" in a regular spruce. Many, but not all, variegated plants arose from such mutations. Another example of a mutation I commonly experience and usually can be noted walking through a nursery happens on "Anthony Waterer Spirea". Often a branch or two on these shrubs will mutate and you'll see a change in leaf form and/or some variegation.

Somatic mutations occur in cells which do not give rise to gametes (gametes are ovaries or think seeds in the case of plants). Mutations that occur in ovaries are called "germinal mutations". These mutations can be from changes during meiosis. These kinds of mutations at times can be passed onto new generations (via seed rather than having to clone) if they are not lethal and usually effect the entire plant rather than just parts. Some germinal mutations can induce sterility and these kinds of plants if desirable must also be cloned.

I am in the process of breeding tomato lines using a germinal mutation for variegation onto potato leafed plants and fruits of different colors.

see
http://kdcomm.net/~tomato/chat/var1.jpg
http://kdcomm.net/~tomato/chat/varPL18_1.jpg http://kdcomm.net/~tomato/chat/varPL_05.jpg

Breeders in the past have used x-rays, radiation or hormones to induce germinal mutations. These kinds of mutations generally effect the whole plant rather than just a part. Breeders do so to create new variation or to help map chromosomes and study gene expression.

Sometimes somatic mutations are not very stable and revert back to the "normal". There is an example of this at the Dairy Queen on 85th and roughly Wornall Rd. There, one dwarf Alberta spruce in a planting has a limb that "reverts" back to the "normal" longer branch form.

The following text lines are links showing images of that tree:
Overall picture of the plant and reversion in center of the plant

Detail comparing reversion area (note the change in color)

Also another reversion example happens with some varieties of variegated plants, hosta and hydrangea come to mind, a single branch or side shoot will revert back to normal rather than variegated.

Chance somatic mutations are sometimes called "sports". That term is often used in tree fruits. Some new apple varieties arose from "sports" rather than conventional breeding. Again they must be maintained by cuttings and often grafted onto hardier rootstocks.

If you find a unique sport and it appears stable you may have discovered the source of a new variety. If ANYONE spots a pink flowered branch on a Bradford pear please contact me immediately!