How Does Photoperiodism | Plant Biology | Khan Academy Work?

Plants use day length to know when it’s time for sleep or wake-up, just like you might use a clock to know when to go to bed or get up.

Imagine your plant is like a sleepy kid who doesn’t want to leave the house until morning. If there are long days, that means it's summer, and the plant knows it's time to grow and bloom! It’s like getting extra playtime during the day. But if the days start getting shorter, the plant thinks, “Okay, winter is coming,” and it decides it’s time for a nap, or maybe even to go to sleep for the whole year!

Plants have special sensors that count how many hours of light they get each day. These sensors are like tiny clocks inside them. When the clock says, “It’s getting dark earlier,” the plant starts preparing, it might grow leaves or flowers, or maybe it will rest until spring.

Some plants bloom only when days are long, and others bloom only when days are short, just like how some kids wake up early and others sleep in! Plants use day length to know when it’s time for sleep or wake-up, just like you might use a clock to know when to go to bed or get up.

Imagine your plant is like a sleepy kid who doesn’t want to leave the house until morning. If there are long days, that means it's summer, and the plant knows it's time to grow and bloom! It’s like getting extra playtime during the day. But if the days start getting shorter, the plant thinks, “Okay, winter is coming,” and it decides it’s time for a nap, or maybe even to go to sleep for the whole year!