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Behind The Blossoms

A close up shot. In the middle of the image is a single tree branch with deep pink buds. In the background, slightly out of focus are light pink flowers and a blue sky.

A robin in a bush. Fresh buds on a branch. For people in colder climates in the United States, those are signs that spring is coming.

Thanks, Phytochromes!

Flowers bud because their phytochrome molecules detect light and temperature, two things that indicate how quickly plants grow. They can be active or inactive, and when they're active, they make a plant grow more slowly. Plants actually grow more slowly during the day than they do at night because sunlight activates the molecule.

During the night, phytochromes switch to their inactive state. The amount of time it takes the phytochromes to make the switch and how long the plant ends up spending growing quickly or growing slowly, depends on the temperature. When it's winter and phytochromes detect cold temperatures that switch takes longer, which means plants spend more time growing slowly.

When temperatures get higher in spring and summer, the switch from active to inactive happens a lot more quickly, which means the phytochromes spend more time in their inactive states, and plants grow quickly.

It takes a lot of work for those beautiful pink-and-white blossoms to appear.

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