Listen to part of a lecture in a botany class.
OK. Last time we talked about photosynthesis, the process by which plants use light to convert carbon dioxide and water into food.
Today I want to talk about another way light affects plants.
I am sure you all know from physics class about how light moves in microscopic ways and that we can only see light when the wavelength of that light is in a specific range.
Plus, depending on the wavelengths, we see different colors.
Well, plants are also capable of distinguishing between different wavelengths of light.
Now, I don't want to confuse you.
It is not like plants have eyes.
Plants don't see in the sense that humans or animals do, but they do have photoreceptors.
Photoreceptors are cells that respond to light by sending out a chemical signal.
And the organism, the plant, reacts to this signal.
In fact, the signals that plants get from their photoreceptors sometimes cause significant reactions.
And many plants are seasonal, and one way they know when winter is ending and spring is beginning is by sensing the change in light.
The time when an adult plant flowers is based on the amount of light the plant senses.
Certain plant species won't flower if they sense too much light and some plants will only flower if they sense a specific amount of light.
Of course, these aren't conscious reactions.
These plants just automatically respond to light in certain ways.
Plants are also able to distinguish between specific wavelengths of light that the human eye cannot even see!
Specifically there's a wavelength called far-red.
Although why they call it far-red … I mean, it is not red at all.
It lies in the infrared range of the spectrum.
We can't see it, but plants can sense it as a different wavelength.
OK. Now I need to mention another thing about photosynthesis.
I didn't explain how different wavelengths of light affect photosynthesis.
When a plant absorbs light for performing photosynthesis, it only absorbs some wavelengths of light and reflects others.
Plants absorb most of the red light that hits them, but plants only absorb some of the far-red light that hits them.
They reflect the rest.
Remember this, because it's going to be relevant in an experiment I want to discuss.