Why Are Leaves Green?

A short summary.

The sun has been shining in the UK today, which means it’s been a lovely day for people to go outside and into their gardens! It’s certainly better than yesterday, where I was outside in the pouring rain…

 

So, naturally, I decided that the thing for me to write about today would be plants! Precisely, leaves. Have you ever wondered why they are green or has it never crossed your mind? Fear not, dear readers, for I am here to tell you!

 

Leaves are the part of the plant responsible for photosynthesis. That means, they convert light energy into chemical energy (glucose) which the plant can use for growth and generally staying alive. The leaves contain chloroplasts, which are responsible for this process. The chloroplasts contain chlorophyll, a pigment. Now, I’m sure from your schooldays you probably remember that a rainbow separates visible light into all the individual colours which it is made up of. Chlorophyll absorbs the colours towards each end of that spectrum. The red and blue ends. Not green. It reflects green light back and away from the plant. That’s why leaves are green. The plant is using the other colours of light to make energy, but not green.

 

So why do leaves stop being green in autumn and winter? Is it because there’s no chlorophyll in them? That’s pretty much it. There’s less light available in the darker months, so the leaf stops making as much chlorophyll. This means more room for different pigments which absorb green light and reflect others. An example of this would be carotene, which reflects orange light, turning leaves that rust colour. Carotene is also, if you hadn’t guessed, the pigment that makes carrots orange.

 

So there you have it. That’s why leaves are green, why carrots are orange and why leaves turn orange in autumn. Pretty interesting, huh?

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