It's Friday, August 3, 2018, and you're listening to Up to Date. I'm Indravis Gontas.

And I'm Kishar Hari. So what do you think plants do to tell the time of day?

Well, I didn't think plants could tell the time, but my guess would be maybe just looking for light.

They have some sort of light sensor in them. Yeah, you think,

but they don't have, they don't have eyes, right? So they can't see light. They don't have,

you know, the kinds of cells that we do that sort of show the, that the sort of peripheral changes in

light. But then there are many plants like flowering plants or sunflowers that seem to track

the movement of the sun across the sky

in some way. Yeah, you might think there could be some sort of chemical reaction happening,

something with like photosynthesis that they're reacting to some of the chemical changes related

to that, and that's helping them track. And then you might think, well, why is it important

for, you know, plants to know what time of day it is? And well, that's because them track. And then you might think, well, why is it important for, you know, plants to know what time

of day it is?

And, well, that's because, you know, pollinators, you know, will come at certain times of day.

So they have to know when to release their scent so that they can encourage those pollinators

to come towards them.

But they also want to make sure that they don't

overuse their energy reserves and therefore, you know, not have enough energy to get through

the night. So scientists have been interested in sort of how plants tell time, and I guess I

really hadn't thought about it for a while. I think circadian rhythms in humans is one of the

most fascinating aspects of our

psychology, since we have so many different biological clocks that track time at different scales,

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