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) 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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