Actually, most orchids do. Fragrant Cattleyas tend to peak around midday, and their contrasting lip color is clearly geared to attracting daytime insects. Brassavolas, Rhyncholaelias, most or all of the Angraecoids, and no doubt lots of others that I don't happen to grow, turn on at night to attract the night flyers. I have often wondered, but never run the experiment, about whether a cut orchid flower continues the cycle or whether it needs to be attached to the plant in order to know if it's day or night.
In a related vein, the reason why "alba" forms (plants that are all white instead of having the dark lip) as well as "peloric" forms (plants in which the other two petals resemble the lip) are rare in nature is because they are at a reproductive disadvantage. The lip, designed to get the pollinator where the plant wants him, is much less effective in these variants.
Bob Zone 7 hoping for some rain tonight
On Thursday, July 1, 2021, 04:20:41 PM EDT, R Hansen via pbs <pbs@lists.pacificbulbsociety.net> wrote:
Jane's comments about Gladiolus tristis releasing fragrance at dusk is
interesting as I've noticed mine are fragrant in the greenhouse during the
day. Will have to pay closer attention.
Her comment that Lilium davidii may be fragrant only at certain times of the
day is fascinating. I can easily check that as I'm nearly always outside in
the evenings working. Hmm, I wonder what else behaves like that??
Robin Hansen
Cool and cloudy on the coast of Oregon
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