Yesterday, here on the North Hemisphere, was the first day of Spring! Yey! Was about time! Altough, the weather isn't warmer, in fact it's windy has hell and it going to rain again. Imagine... But let's hope that it'll get better. And today it's the day of the tree, so it's time to celebrate the explosion of life that happens this time of the year.
And while on this topic, didn't you ever wonder how does flowers know that's time to blossom? How they are correctly timed, even in years that the sun comes earlier or in years that sun it's late? And how does the winter plants only blossom on the winter?
Saucer Magnolia Tree (Magnolia × soulangeana)
It's something quite simple, called photoperiodism. In other words, it's the time exposed to daylight that gives the "tic-tac" time to plants to know that is time to blossom.
First, we need to know that are short day plants and long day plants, and that exists a protein that's translate to the plant the stimuli from the sunlight called phytochrome. The phytochrome has two interconvertible forms, the F form (that absorve far-red light) and the R form (that absorve red light). When the F form absorve light with 730 nm transforms to the R. The sunglight has the two kind of lights, so during the day we have the two forms of the phytochrome, more F then R. At night, like the F form is more instable, it changes back to the R form.
And you ask, why is this important? Because that's the F form of the phytochrome that says it all!
In the short day plants, the F form acts like an inhibitor of the blossom. As I said, during daylight we have more F form. So in short day plants, they blossom when the night time is longer, because as the dark time it's bigger we will have more F form changing back to the R form.
In the long day plants, the F form acts like an inductor. So as the light time is bigger, during the dark time that it's smaller there are no total conversion of the F form to the R form. And that's why the flowers don't blossom in the winter, because even if it is a warm year, the dark time aka night is too long and the R form don't induct the blossom.
Of course not all plants answer so clearly to this happening. Some of them need a rise or low of the temperature, and others need other kind of stimuli. But to a lot of plants it happens like this. Cute isn't it? Something so simple that bring to us the colors of the spring.
Even Sam it's curious about the flowers. In fact I think he is more curious to eat them.
This is a wild orchid that we saw last year in May in a field trip to the Parque Natural de Montesinho, in Bragança.
And this Crocus, belongs to the same gender to the saffron, Crocus sativus. It's an example of a flower that blooms on the Autumn.
Sofia G. and Sofia S.