Fragrance update
Roy M. Sachs (Wed, 10 Jul 2002 10:56:39 PDT)
Some weeks ago, May 10th to be exact, on that other forum, Jane
McGary contributed the following in the form of a question,
Can anyone explain the mechanism by which flowers emit fragrance at
particular times of day? I know that many flower scents are detectible only
in warm temperatures, regardless of time of day, but others are detectible
primarily in the late afternoon and night, whether the flowers are open or
not. What actually happens, physiologically, when the fragrance is emitted?
I was moved to ask this because I have some flowers of Gladiolus tristis in
the house right now. Their beautiful scent is not very strong in the
morning, but in late afternoon it suddenly strengthens, even though they
are on cut stems in a room with artificial light as well as daylight.
Most night-scented flowers seem to be light-colored (like this pale yellow
gladiolus) and are said to attract moths as pollinators.
Over 40 years ago I worked a bit on release of fragrance from excised
corollas of Cestrum nocturnum (night-blooming jasmine)...it turned
out that even the excised corollas were most heavily scented in the
evenings as if the circadian control was due to mechanisms localized
in the coralla and not the entire plant....but we didn't go further.
it turns out that there is marvelous stuff going on.
In the June 28th issue of Science (vol. 286 p 2327-2329) there is a
review of some recent work on fragrance in Clarkia and Antirhinnum.
In Clarkia 8 to 12 major compounds were discovered related to their
characteristic aroma and the researchers isolated an enzyme in the
petals that catalyzes the synthesis of one of linalool (common to
many flowers). Now 3 other enzymes have been characterized and
they're mainly in the epidermal layer of the petals.
The research offers promise for a) understanding the biochemistry and
timing of release of aroma from flowers,and b) through genomic
studies, which intend to identify the genes controlling the pertinent
enzymes, the hope of re-introducing scent to species where scent has
been lost in the course of breeding programs (where the primary goals
have been bloom size, color and vase life).
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