Plant of the Week
Blue Carnation - Moondust
Latin: Dianthus caryophyllus
The search for flowers with shades and hues different than what nature
provides has been ongoing since humankind discovered the intricacies of plant
breeding. But, there are limits to the color range that can be achieved using
traditional breeding techniques. For example, blue pigments are lacking from
many plants.
But science now allows breeders to extend the natural range of colors, using
genetic engineering. ‘Moondust’ carnation, first grown commercially in 1997, is
a mini-carnation with purple-mauve flowers that gets its blue color from petunia
genes grafted into the DNA of the carnation.
Twelve scientists at an Australian company called Florigene labored for a
decade to isolate the gene responsible for blue color in petunia and then
transfer it into the carnation. To date, they have released five carnations with
the "Moon" prefix, all with varying shades of mauve, blue, violet or purple.
Flower color expression is caused by the subtle blending of pigments
contained in the vacuoles (think of vacuoles as storage closets in the cell) and
plastid bodies (think of these as like chlorophyll, but with a color other than
green) suspended in the cell sap. Just as the man at the paint store blends
different pigments to a neutral base to color paint, flower color is caused by
the subtle blends of several pigments.
But roses, carnations, lilies and orchids all lack a class of blue pigments
called delphinidins, named after the violet-blue we see in delphinium. The gene
for delphinidin production is what the Floragene scientists removed from petunia
and transferred to the carnation.
The development of the blue carnation was not the primary goal of the
research team; no, they wanted to make a blue rose. But, transplanting genes is
easy to say but hard to do in the lab, so they honed their techniques on
carnations - a much easier species to manipulate than roses. The team has not
given up on the idea of a blue rose, but it is now exploring the possibility of
inserting genes from sea anemones into the rose to create the blue shades. The
petunia gene didn’t work in roses.
You may be thinking by now, "I’ve seen blue carnations for years. What’s new
about this?" True, there have been blue carnations available since the 1970s,
but their blue was due to food color, not natural pigments.
Scott Admire with Little Rock’s United Wholesale Florists says they used to
dye white carnations shipped in from cut flower growers in Central and South
America. The carnations would have to be shipped in as a "dry pack"; exposed to
neither water nor the floral preservative silver thiosulphate. The carnations
would then suck in the pigment-laden water with a good deal of it ending up in
the petals, turning the flowers the shade of blue you see atop a decorated
birthday cake.
Floragene is marketing the blue carnations in the U.S. market, but Scott has
not seen them in the Little Rock market. The Internet indicates the few
distributors that are receiving them are primarily on the east and west coast.
Carnation flowers sometime get "sleepy" and curl up. This is caused by the
production of a plant growth hormone called ethylene, which is a part of the
natural aging process in flower development. Cut flower growers combat this by
using the silver-containing floral preservative that stops the production of
ethylene. Floragene scientists are currently seeking clearance to introduce a
line of plants that do not produce ethylene, thus eliminating the need for the
silver thiosulphate treatment.
This ethylene-blocking technology is not new, and in fact, an Arkansas boy -
Dr. Randy Woodson from Fordyce and now a Dean at Purdue University responsible
for the agricultural research program - patented a technique in the early 90s
using the "anti-sense" procedure. Using this technique, the gene for ethylene
production is switched end-for-end in the DNA strand, rendering it inoperative.
It's not clear if the Floragene technique uses this same "anti-sense"
technology.
Are the scientists involved in creating genetically modified plants playing
God? What about environmental concerns? For the former question, my theological
credentials are suspect, but to the latter question I feel confident there is no
significant environmental risk in growing blue carnations. The plants are
essentially pollen sterile and carnations are harvested in the tight-bud stage,
so the likelihood of out-crossing with wild carnations is remote.
By: Gerald Klingaman, retired
Extension Horticulturist
- Ornamentals
Extension News -
May 7, 2004
Back to Archives A - D
|
