I've been trying to discover why Drosera flowers vary in nature
here in Brazil and though I don't have any conclusions yet, I have strong
suspicions. The species which probably varies the most is D.communis,
having flower from pure white to lilac. Of the native Brazilian
species, I'd say this one is the most similar to D.rotundifolia and is
probably its closest parent down here. By what I've seen, 2 ecological
factors are surely involved with flower color. These are sunlight
intensity and soil humidity. When the soil is drier and the sunlight more
intense, the flowers are lighter in color and vice versa. I recently went
to a D.communis site near S.Paulo city where the plants had lilac
flowers. The funny thing is that when I went there around 2 years ago,
all plants had light-lilac flowers, almost white. Back then it had been
rather sunny and dry (I think) for a few weeks and this time it had been
raining intensely over the previous few weeks. Thus it would be the
opposite of what's happening to your D.rotundifolia flowers, which are pink
and right up against the lights. Another factor I think influences flower
color is pH. I'm not sure if alcaline soils promote plants to
produce lighter-colored flowers and acidic soils make them darker or vice
versa. I think soil pH might even be more important than humidity since
I've found D.communis with white flowers growing in one boggy area and
light-lilac flowered ones growing 1 or 2km away. I've noticed that some
regions often have just one or the other color and sometimes they're
even mixed in the same bog! It might be some other chemical in the soil,
who knows?!
I don't know if any of you remember a "News and Views" in CPN
written by Peter D'Amato many years ago, mentioning that his U.subulata
produced a clear mucilage on their flower scapes, like the mucilage on the
Drosera tentacles. Only it was more viscous and he said he could stretch
a string of this mucilage a long way before it broke, longer than you'd
expect anyways. There was even a B&W picture showing this. I've recently
noticed that 2 other Utrics in the same section of the genus also have
this mucilage, which is apparently produced at the axils between the
pedicels and the peduncles. These are U.pusilla and what I believe to be
U.nigrescens. I keep wondering what this is mucilage on the peduncles is
for. Could it be defense against aphids or something? I recently found a
site near S.Paulo city with the large aquatic U.foliosa and the peduncles
were covered with aphids. Anyone have any ideas?