Why is...?

Question

Ok, everyone knows about chlorophyll! What I mean is, why is chlorophyll green, why do they choose green??

Answer 1

The chloroplasts in plants cells contain chlorophyll which is of a green pigment. This pigment is what we see reflected from the plants.

Answer 2

My theory: Effect of coloured compounds most efficiently absorbing solar energy.  The particular colour depends on the environment to which the plant is adapted, and an interesting tradeoff between absorbing shorter wavelength light (more energy per photon) and light at the wavelengths where the sun is strongest. What's your theory?

We are good at seeing different shades of green, and tend to find them pleasant. Effect of evolution for food gathering.

Answer 3

clorophyll

Answer 4

This is kinda a  philosophical scientific question (No hard proof other than conjecture), but I believe Paul (so, possibly your theory too).

Answer 5

What you are asking about is the 'Green Gap' in chlorophyll. Why does a plant's photosynthesis absorb to either side but reflect the green wavelengths? Why reflect any light why not absorb it all?

The very short UV is very risky and causes plants as much damage as it does us. There is plenty of sunlight and it is less important to use it with maximum efficiency than it is to prevent UV damage to the  photosynthesis center and the plant in general. Light is handled by many accessory pigments to take this very risky energy source and shelter the plant from photochemical damage while harvesting enough energy to live. Today there are accessory pigments that aid in protection and photosynthesis and some that protect only like the xanthophyll cycle.

http://www.img.cas.cz/bl/64_1_053-067.ht...

http://www.lbl.gov/Science-Articles/Arch...

Photoinhibition

http://en.wikipedia.org/wiki/Photoinhibi...

It is advantageous for a plant growing in a hot climate or the tropics to reflect sunlight not used for growth. They may grow fine hairs or use other mechanical means to shelter but at some point they must allow the light in with all its risks. Then the only protection is in reducing the light energy to a harmless level.

http://www.pnas.org/cgi/content/extract/...

Why is green specifically reflected and not blue, red or orange? That is due to the actual shape of the molecule chlorophyll a. It happens to have chemical bonds that absorb in two wavelengths. However it absorbs very well at the red end that penetrates and warms water so was the best that was available to the original phototrophic organisms that were aquatic bacteria. Chance gave the progeny that carried this  photosynthetic molecule the advantage. They are the ones that became symbiotic as chloroplasts in eukaryotic protists to become ancestral to the green algae and plants.

Evolution has altered the basic chlorophyll into other forms that absorb different wavelengths as a result. Chlorophyll b, which is a chlorophyll a modified to absorb more in the blue spectra, has an methyl side chain altered to a formyl group.

http://users.rcn.com/jkimball.ma.ultrane...

Variations in green are due to differences in light absorption. Plants do not all have the identical ratios of pigment types.

http://www.botgard.ucla.edu/html/botanyt...

http://www.pubmedcentral.nih.gov/article...

Halobacteria are photosynthetic but use no chlorophyll and reflects purple.

http://www.science.siu.edu/microbiology/...

http://www.nature.com/nature/journal/v27...

http://www.pubmedcentral.nih.gov/article...

Melanin for photosynthesis in shades of brown?

http://www.physicsforums.com/archive/ind...

http://www.physicsforums.com/showthread....

http://www.physicsforums.com/archive/ind...