1. how do the yellow petals of dandelions become those white fluffy things (briefly)?

2. how long does the transformation take?

2. does it take place only at night?

basically i would like a resolution to a great mystery.
i have examined hundreds of dandelions, during the season that they are turning from yellow to white.
i have NEVER found a transitional stage!
they are always completely yellow flowerish or completely white parachutish.

thank you

Ok, I've been talking to the curator of biology in Bristol (who is a botanist) and she has says she's not certain but:

1. They don't - the papus (the parachutey bit) develops around each seed. Dandelions are composite flowers (like daisys and sunflowers) so the petals are actually a fringe around a head composed of lots of tiny little flowers.

2. Unsure. The time taken will probably depend on temperature, but much of the development will take place while the petals are still on the flower.

3. Dandelions close at night, and like all plants they may not obtain energy during the day, but they are busy using up stored energy. It seems likely that the final stages before the "clock" emerges will take place while the flower is closed (which might possibly last a few days), then it will open when the sun is strong enough to dry the papus (thus opening erach parachute) and the seeds can disperse. This reliance on the sun means that the flower will stay shut on rainy days when the seeds would be less likely to disperse.

Have a go at picking some closed dandelions (especially ones closed during the day) and cutting them in half - you might find some transitional features.

I can't guarantee that this is entirely accurate, but it's an answer of sorts! Let us know if you find anything to contradict or confirm our description!