My five year old asked me why plants and leave are green as opposed to being black, blue, silver, golden, etc. I know about plants containing chlorophyll but how do I explain it to her without sounding all science-y?
In: Biology
They absorb all incoming wavelengths of visible light except for green, which gets reflected back into our eyes, making them appear green.
Plants don’t eat – instead they get their energy from light. They have a chemical in their leaves that absorbs light, and it’s called chlorophyll.
Chlorophyll only works with red and blue light. Chlorophyll isn’t shaped right to absorb green light, so that bounces off and hits you in the eye, and that’s why you see green when you look at a plant.
(I’m guessing this will quickly pull the conversation away from photosynthesis, and into how colors and vision work. She might be interested to hear about how if a plant was black that would mean it was absorbing all the light, which would mean it’s super good at getting energy, and a silver plant would starve because all its food/light is bouncing away and so none is being soaked up.)
Imagine that sun throws a lot of red, blue and green little balls at the plant. The plant eats the red and blue balls to get bigger, but it doesn’t like the green ones and throws them away. They hit us in the eye and so we see the plant as green.
So, plants are green specifically because they reflect green light instead of absorbing it for photosynthesis.
Why they reflect it isn’t actually a settled answer, but to my knowledge one serious proposal is because there’s just too much green light in sunlight to safely handle, and so they do it to prevent damage to the light sensitive molecules that perform photosynthesis.
There are photosynthesising algae on the sea that do absorb green light, likely because water already absorbs light, so there’s no risk of overexposure and the problem instead flips to getting as much light as possible.
Chlorophyll the part of plants that converts sunlight into energy into energy that the plant can use are green the green part of the spectrum is the least useful part in producing energy so it is reflected making most leaves appear green. https://youtu.be/sBUmjEAhN3o
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