| Albas &
Albinism :
Pure colour is the term Alvin Bryant first
used in the 1960's to describe Cymbidiums whose floral segments were free from
"sun staining"
or red pigment production . More correctly these Cymbidiums
are called albas. In Cymbidiums albinism refers to the inability of
the plant to produce red pigments (anthocyanins). More than five enzymes are
required to synthesize these pigments, each working in concert. Any even minor
disruption in any of the mechanisms of these enzymes by either genetic or
environmental factors would halt anthocyanin production. Due to a genetic fault
(actually a missing enzyme) albinism is expressed in Cymbidiums as a non
staining , pure colour of the floral segments and complete absence of red
pigmentations in both the plant and its flowers. Thus we see white, yellow and
green alba flowers or combinations/ variations of these colours.
|
One of the major roles of anthocyanin-related pigments is to serve as a UV screen and they are produced in response
to exposure of the plant to UV radiation, protecting the plant's DNA from damage
by sunlight. (UV causes the paired strands of genetic material in the DNA double
helix to become cross-linked, preventing cell division and other vital cellular
processes like protein production). The red pigments in Cymbidium flowers
normally play a role in helping to protect tissue from "burning" or damage
due to extremes of temperature and light, some alba varieties are prone to
"burning" of the labellum from exposure to high and/or low temperatures. As well
there tends to be a higher incidence of abnormal meiosis in albas leading to ploidy changes in the
progeny of some alba varieties or even infertility in some alba lines. |
