Why is chlorophyll green? Isn't there a more energetically favorable color?

Why is chlorophyll green? Isn't there a more energetically favorable color?

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Chlorophyll being green means it absorbs light in the red and blue area of the spectrum. Isn't this the high and low energy light? Wouldn't plants get more energy if they absorbed light in the green area of the spectrum instead of the red one?

The reason that chlorophyll is green is because it absorbs other colors of light such as red and blue, so in a way the green light is reflected out since the pigment does not absorb it.

Because life might have been purple:

It is possible that the very first life form to process light may have been purple colored. This would mean it was reflecting red and blue light and absorbing green. In such a scenario this thing if it was the first to produce energy from light would have out competed against everything else. It would have had a population explosion and possibly covered much of the Earth or at least the oceans. Haloarchaea are an example of a simple life form that uses Retinal and Bacteriorhodopsin to produce energy though far less efficiently than photosynthesis. Had this been developed prior to photosynthesis it may have let it spread very far even though it is a less efficient energy production method. A 2% efficiency increase in a market no one has yet tapped is still a huge advantage.

In this scenario because the first thing to use light was using green light it left a niche for another form of life to exploit. That niche would have been absorbtion of the Red and Blue spectrums. Which is the same area plants absorb today. They got so good at their niche that they eventually were able to generate much more energy than the first life form did and eventually out competed for the sun. This niche has worked so well that they never developed a full system for the other spectrums.

Because you could say that good enough is good enough:

The sun puts out a lot of energy. It is possible that there was no need to try and capture all of the spectrum or that it was actually not beneficial to do so. Often too much sun is more an issue than too little. Too much sun and heat can dry out the plant. It is possible that to gain the benefits of photosynthesis there needed to be a reduction in some energy to balance it out. Much like a black car on a hot summer day a black plant might absorb all of the spectrums but also get far too hot. Blue plus red may just be the sweet spot.

However, about your question about colour:

Wouldn't plants get more energy if they absorbed light in the green area of the spectrum instead of the red one?

Plants would probably get more energy if their leaves were black.


A viewpoint: Why chlorophyll a?

Chlorophyll a (Chl a) serves a dual role in oxygenic photosynthesis: in light harvesting as well as in converting energy of absorbed photons to chemical energy. No other Chl is as omnipresent in oxygenic photosynthesis as is Chl a, and this is particularly true if we include Chl a 2, (=[8-vinyl]-Chl a), which occurs in Prochlorococcus, as a type of Chl a. One exception to this near universal pattern is Chl d, which is found in some cyanobacteria that live in filtered light that is enriched in wavelengths >700 nm. They trap the long wavelength electronic excitation, and convert it into chemical energy. In this Viewpoint, we have traced the possible reasons for the near ubiquity of Chl a for its use in the primary photochemistry of Photosystem II (PS II) that leads to water oxidation and of Photosystem I (PS I) that leads to ferredoxin reduction. Chl a appears to be unique and irreplaceable, particularly if global scale oxygenic photosynthesis is considered. Its uniqueness is determined by its physicochemical properties, but there is more. Other contributing factors include specially tailored protein environments, and functional compatibility with neighboring electron transporting cofactors. Thus, the same molecule, Chl a in vivo, is capable of generating a radical cation at +1 V or higher (in PS II), a radical anion at −1 V or lower (in PS I), or of being completely redox silent (in antenna holochromes).

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Why is chlorophyll green? Isn't there a more energetically favorable color? - Biology

That is a great question, light is a very tricky thing as it comes in various forms of energy levels. UV light (close to purple and blue) is very high energy and that's why we get sunburned. On the other side of the spectrum is Infrared (close to red) which is seen in night vision goggles and can be seen from heat emitting from our bodies, a relatively low energy light. Plants, just like us can only tolerate certain wavelengths of light, especially for the chemical reactions of photosynthesis. Photosynthesis occurs when pigments, molecules in the plant cell, absorb light photons and transfer them around to create chemical energy. These pigments are picky in terms of which light they can use. There are two types of Chlorophyll pigments, A and B. Chlorophyll A absorbs a lot of red and some blue while Chlorophyll B absorbs a lot of blue and some red. Neither absorb green much which is why plants appear green.

Chlorophyll absorbs red light. No light gets absorbed by chlorophyll means the plant can't do photosynthesis.

Trees and plants are green because of a green pigment called chlorophyll. This pigment absorbs red light the best, and converts the light into energy that it uses for metabolism. As you likely know, this pigment allows plants to use light as a form of energy, as a part of a process called photosynthesis. Instead of eating food to build molecules, plants can take light from the sun and use the energy to convert carbon dioxide from the air into useful molecules! However, the pigment doesn't strongly absorb blue or green light, so plants can't use this energy for photosynthesis. Interestingly, we know this even from the color of plants! White light contains all the colors, and plants appear green because they absorb the red light, leaving what appears to us as green light, to be seen by our eyes! If the light isn't being absorbed by the plant, it can't be used for photosynthesis!

Separating leaf pigments using thin-layer chromatography

This article presents a simple laboratory experiment to understand leaf pigments. Students use thin-layer chromatography to separate the various pigments that are present in two different leaf extracts. They identify each pigment and determine whether the two extracts have any pigments in common. The experiment is suitable for students aged 11–16 and takes 1–2 hours to complete.

Note that we used leaves from Epipremnum aureum (commonly known as devil’s ivy) and Ficus benjamina (commonly known as weeping fig), but any species could be used for the leaf extracts. You might also like to carry out the experiment using a brightly coloured flower, such as those in the Petunia genus, and also a yellow or orange leaf.

Leaves of Epipremnum aureum, commonly known as devil’s ivy
Joydeep/Wikimedia Commons, CC BY-SA 3.0

Leaves of Ficus benjamina, commonly known as weeping fig
JM Garg/Wikimedia Commons, CC BY 3.0

For the thin-layer chromatography, we use a combined mobile phase of hexane, acetone and trichloromethane (3:1:1) as it provides the best separation result. However, it requires part of the activity to be carried out inside a fume hood by the teacher. This mobile phase separates the pigments most clearly, but you could adapt the activity to use mobile phases of hexane or ethanol alone, which the students can carry out themselves. Both hexane and ethanol successfully separate the pigments, but the distinction between each pigment is not as clear as when the combined solvent is used.


  • Leaf samples (e.g. E. aureum and F. benjamina), cut into pieces measuring approximately 2 cm x 2 cm
  • Thin-layer chromatography plates (10 cm x 5 cm) pre-coated with silica gel
  • Organic solvent comprised of:
    • 3 parts hexane, C6H14
    • 1 part acetone, (CH3)2CO
    • 1 part trichloromethane, CHCl3

    Safety note

    A lab coat, gloves and eye protection should be worn. The solvents used in this experiment are flammable, so they must not be used near flames. The combined solvent (hexane, acetone and trichloromethane) must only be used inside a fume hood due to the volatility, smell and health risks associated with it.


    The following steps should be carried out by the students:

    1. Place your first leaf sample in the mortar. Pipette 1 ml of acetone into the mortar and use the pestle to grind the sample until the leaf is broken down.
    2. Transfer the mixture to a well of the spotting tile using the pipette.
    3. Wash the mortar and pestle, and repeat steps 1–2 using the second leaf sample. Use a new pipette to add 1 ml of acetone and use this pipette to transfer the mixture to a new well of the spotting tile.
    4. Take the chromatography plate and draw a horizontal line 1.5 cm from the bottom using a pencil. Take care not to touch the plate with your fingers.
    5. Using your first pipette (take care not to mix up which pipettes were used for each leaf sample), draw up some of your first leaf sample. Apply a single, small drop to the pencil line on the left hand side of the chromatography plate. Make sure to leave enough space to fit the second sample on the right hand side.
    6. Wait a few seconds until it dries, and apply a second drop on the same spot. Continue until you have added around 10 drops.
    7. Using your second pipette, repeat steps 5 and 6 for the second leaf sample by adding it to the right hand side of the plate.
    8. Allow the plate to dry completely.

    The following steps must be carried out by the teacher:

    1. Inside the fume hood, combine the solvents in the following proportions: hexane, acetone and trichloromethane, 3:1:1.
    2. Add the combined solvent to the beaker. You should add only a shallow layer of solvent, so that the pencil line on the chromatography plate will not be submerged.
    3. Place the chromatography plate vertically into the beaker, with the pencil line at the bottom, and cover the beaker with a watch glass. Students can watch as the solvent moves up the plate and the pigments separate.
    4. Wait until the solvent has travelled roughly 6 cm from the starting point (this will take approximately 15–30 minutes) before removing the plate from the beaker, leaving it inside the fume hood.
    5. Use a pencil to quickly mark the furthest point reached by the solvent. Allow the plate to dry completely before removing it from the fume hood.

    The following steps should be carried out by the students:

    1. Photograph the chromatogram as soon as it is dry. The colours will fade within a few hours. Print out a copy of the photograph for your notes.
    2. Using the chromatogram photo, try to work out how many pigments are present in each leaf extract.
    3. Now look at the chemical structures of different pigments (see figure 1). Can you determine which pigment is which (see the explanation section for more guidance)? Write down your answers.
    4. Measure the distances travelled by the solvent and the pigments, and calculate the retardation factor (Rf) using the following equation:
      Rf = (distance travelled by pigment) / (distance travelled by solvent)

    Record your results in a table. Compare these to the values in table 1: were your answers correct?

    Figure 1: Chemical structures of photosynthetic pigments: chlorophyll a and b, β-carotene, and violaxanthin (a xanthophyll pigment). Polar groups circled in blue, nonpolar groups circled in red. (Click to enlarge)
    Nicola Graf


    The different pigments in a leaf extract are separated based on their affinities for the stationary phase (the silica on the thin-layer chromatography plate – a polar substance) and the mobile phase (the solvent – a nonpolar substance). Compounds with a high affinity for the solvent (i.e. nonpolar compounds) will move much further than compounds with a high affinity for silica (i.e. polar compounds).

    In our example (see figure 2), both leaf extracts contained four pigments. Pigment 4 moved a shorter distance than pigment 1, indicating that pigment 4 is more polar and pigment 1 is less polar. By looking at the chemical structures of different pigments and the polar and nonpolar groups, students can try to identify the pigments in each of the leaf extracts.

    They will need to know that, of the functional groups present in the pigments in figure 1, alcohol groups are the most polar, ester and ether groups the least polar, and aldehyde and ketone groups are in between. From this, we can deduce that carotenes are the least polar pigments (no polar groups), and xanthophylls are the most polar (two alcohol groups, one at each end of the molecule). Therefore, pigments 1 and 2 are likely to be carotenes, and pigment 4 is likely to be a xanthophyll. Pigment 3 is likely to be chlorophyll, since it is more polar than carotenes but less polar than xanthophylls. You can observe the characteristic green colour from chlorophyll on the chromatogram.

    Figure 2: Chromatograms and corresponding Rf values for two leaf samples (E. aureum and F. benjamina) using a mobile phase of hexane, acetone and trichloromethane
    Josep Tarragó-Celada

    Now look at the Rf values, which range between 0 and 1, with 0 being a pigment that does not move at all, and 1 indicating a pigment that moves the same distance as the solvent. The Rf value varies depending on the solvent used, but the general order of the pigments (from the highest to the lowest Rf value) usually remains the same, because the nonpolar compounds move further than the polar compounds. Rf values for various pigments (using hexane, acetone and trichloromethane (3:1:1) for the solvent) are shown in table 1.

    Table 1: Rf values for a variety of plant pigments, calculated from a chromatogram using hexane, acetone and trichloromethane (3:1:1) for the mobile phase (Reiss, 1994).
    Pigment Rf value
    β-carotene 0.98
    Chlorophyll a 0.59
    Chlorophyll b 0.42
    Anthocyanins 0.32-0.62
    Xanthophylls 0.15-0.35


    After the experiment, you can ask your students some of the following questions to gauge their understanding of plant pigments and thin-layer chromatography.

    Enter: Chlorophyll

    If you've researched chlorophyll before, you've probably seen it advertised as nature's deodorant. Indeed, one of the most widely recognized and broadly promoted benefits of chlorophyll is that it can reduce bodily odors as a sort of natural deodorant. The question is… is that true, or not?

    Chlorophyll's reputation as a deodorizer comes from a study performed decades ago, specifically in patients with colostomy bags. For those who don't know, a colostomy is a surgical procedure that bypasses the colon, redirecting the end of the intestines to an artificial opening, where feces collects in a bag. This, for obvious reasons, can be a source of unpleasant odors. Many, many things have been tried to help reduce this, from upgrades in the technology used to create and seal the bags, to supplements like chlorophyll.

    Indeed, a study performed ages ago found that chlorophyll supplements could reduce the odor of colostomy patients. That study, performed in the 1950s by Howard Westcott, forms the basis of modern chlorophyll deodorizing benefits.

    As for how it works, well, that's not really well understood. Some people theorize that chlorophyll binds to the molecules that bacteria would otherwise use as food. Since the chlorophyll isn't broken down in your digestive system all that well, the molecule is trapped and excreted, free of bacterial exposure. The bacteria left with less to eat, don't produce as many odor-causing compounds. Thus, depriving the bacteria of food means fewer bad odors.

    Additionally, chlorophyll – and more specifically, the vegetables that are high in chlorophyll – also form a great source of antioxidants and other beneficial compounds. A healthier body produces fewer bad odors. (This, again, goes back to evolution you are tuned to view the sick as disgusting, so you instinctively stay away from them, to avoid getting sick yourself.)

    Everything you know is wrong: Oranges aren’t orange.

    Oranges weren’t named for their color – because their color often wasn’t orange. Find out how they get their brilliant hue, why many ripe oranges have to be dyed, and why nothing in the world is what you think it is.

    While the name origins of many fruits are a mystery, the orange seems like a no-brainer. It was named for it color. Actually, use of the word ‘orange’ to describe a cross between red and yellow wasn’t recorded until three hundred years after the fruit appeared in Europe. It’s thought that oranges get their name from the Sanskrit word for fragrant – naranja. And although the flesh of oranges does flare a tasty-looking orange, the skin of many oranges, especially in the ones in warmer countries, is green.

    Many fruits are picked while they’re still a little green and left to ripen during transport, in the store, or just become hard little fruit-bombs in a bowl in peoples’ homes. Most green oranges, on the other hand, are perfectly ripe. By the time they turn orange they’re sliding downhill towards rot. The green skin of an orange isn’t indicating that not enough of its natural color is coming through. It’s just pumped full of chlorophyll. In warm, sunny countries, that chlorophyll stays in the fruit. It’s only when the fruit is exposed to cold that the chlorophyll dies off and the orange color shines through.

    In South American countries and tropical countries near the equator, oranges stay green all year around. In the United States, oranges grown in early spring or ones that are grown in late fall turn orange naturally. Ones that only see the height of summer are usually green. To make it even more frustrating for farmers, oranges that have killed off their chlorophyll can green up once again by sucking the chlorophyll out of the leaves around them like small, tasty vampires.

    Since most people associate green fruit with unripe fruit, most green oranges in the United States and Europe have to be colored to be sellable. In some cases they are exposed to ethylene gas, which breaks down chlorophyll. Some are shocked with cold, or covered in wax. Some are scrubbed down with detergent and some are just dipped in dye. Anything for a sale.

    The Scientific Difference Between a Ripe and an Unripe Banana

    There are two types of bananas, unripe and ripe. Some people like them green others love a nice mushy brown banana. Each kind of banana has certain benefits. We’ve got the lowdown on the good, the bad and the ugly when it comes to bananas.

    Unripe Bananas

    Photo by Jillian Skowronski

    Unripe bananas appear green and waxy. They are firm and bitter to the taste with about 40 percent starch. The low glycemic index makes it take longer to digest.

    Green bananas have a high resistant starch content and a low sugar content. So those who suffer from Type 2 Diabetes are better off eating a green banana than a yellow one. Unripe bananas have a probiotic bacteria that helps with good colon health. Green, unripe bananas also help you absorb nutrients, like calcium, better than ripe bananas can.

    Unripe bananas have low antioxidant levels because these increase with the age of the banana. Green bananas may cause some bloating and gas due to the higher resistant starch content.

    Ripe Bananas

    Photo by Jillian Skowronski

    A ripe banana is yellow with brown spots and is soft. There is an increased flavor, especially sweetness. It contains 8 percent starch and 91 percent sugar. The high glycemic index makes ripe bananas easy to digest.

    Yellow, ripe bananas are easier to digest because the resistant starch changed to a simple sugar. Bananas also obtain higher levels of antioxidants as they ripen. Fully ripened bananas produce a substance called Tumor Necrosis Factor (TNF). This gives ripe bananas anti-cancer qualities as they combat abnormal cells in your body. With more age and dark patches, the banana has a higher immunity enhancement quality.

    There is some micronutrient loss that happens with age of a banana. To lesson the vitamins and minerals lost, store bananas in the fridge. But be careful, because this makes them brown quickly. Also, the high sugar content makes ripe bananas a snack people with Type 2 Diabetes should avoid.

    Top Image Source:

    Colour. I can’t live without it. I need bold and colourful rooms, playing with as many colours as possible and for me it’s about earthy Autumnal colours browns, greens, ochre, orange, plum. That’s what makes my heart sing from an interiors perspective.

    Moreover, it seems that colour and colourful interiors are here to stay for a little while yet. There has certainly been a trend towards the use of bolder colours in interiors in recent years, and why not?

    Colour, used in the right way, can evoke all sorts of emotions and make your interior a happy place to be. Used in the wrong way it will be bland and can sap your energy, affect your sleep and even cause your digestive system to either go into overdrive, or slowdown.

    So, let’s explore Colour……. and why it is such a powerful tool to use in your interior space.

    Colour Psychology-The Science Bit

    What colour represents to you or me, may be very different, as each of us have our own preferences for the colours we like to wear or decorate with.

    However, there is a whole field of colour physiology which looks at how colour influences our moods, our choices, even our behaviour. The colours we choose say a lot about our personalities, as we each process colour differently in our brain. Finding a colour that works for you, in your home, is as important a decision as the design ethos you are going to follow.

    And, it is okay to choose a colour that isn’t “on trend”. If you prefer black, that’s fine. If you prefer deep red, that to. Remember, we are all individual in that sense, and just because yellow is perceived to be a happy colour, doesn’t mean it will be for you.

    Colour is fundamental to interior design and decorating. The choices we make affect the way our homes look, the way our homes feel to us and today, I am focusing on GREEN, my favourite colour.

    I wonder what that says about my personality?

    The most chameleon of colours, now associated with serenity and calm, was once considered deadly poisonous. Green has undergone something of a revolution since the 17th and 18th century, when historians believed it may have contributed to the death of Napoleon Bonaparte, to the symbol of life and growth, environmentalism and conservation.

    Image Source:

    It strikes the eye in such a way as to require no adjustment whatsoever and is, therefore, restful and soothing. It carries association with sincerity, health, fertility and good luck (green is the colour of a lucky clover). Dark green is associated with money. It is also associated with jealousy.

    It is the sign of growth, new life, Spring. In nature, it is the result of chlorophyll, which enables plants to convert sunlight into energy. This is what gives them their green colour. Remember your biology lesson anyone?

    Negatively, it can indicate stagnation, it slows down metabolism too, and, incorrectly used, will be perceived as being too bland.

    Researchers have even found that green can improve reading ability. The use of green can signify intelligence and confidence.

    Green for various cultures is also the shade illustrating the divine and religious figures. In the Muslim world, the colour green is strongly related to the Prophet Muhammad in England, the color has heroic meanings and it is connected to the stories of Robin Hood in China, the color represents disgrace, while in Japan green signifies eternal life.

    In more recent years, green has taken on a whole new meaning and is now used to describe a wide array of practices, and ideas, be it recycling, the reduction of carbon emissions or growing your own food.

    The History of Green

    Introducing green to the art world in 1775, Swedish Chemist Carl Scheele produced a deadly green pigment known as Scheele’s Green, which was used throughout Victorian age, regardless of the fact that it was suspected, by many, to be dangerous. This colour contained green pigments but also deadly arsenic. The fact that this was used the coloring of Napoleon Bonaparte’s bedroom wallpaper forces many historians to believe that Scheele’s Green caused the revolutionary’s death in 1821.

    The deadly combination was replaced in the 19th-century with the mixture of copper and arsenic, which was used in many impressionist paintings by Cezanne and Monet. Not surprisingly it was banned in 1960.

    Decorating with Green

    Image Source.

    Ever since Pantone named green its colour of the year in 2013 (Emerald) and again in 2017 (Greenery), green has been a popular choice in interiors. But, you need to be sure that green is the right colour for you before you go ahead and decorate with it.

    Like all colours it has to resonate with you, you need to feel comfortable with it or you will simply regret starting your scheme.

    Green is around in wallpapers, accessories and furniture, so if you don’t want to go all out and paint a room green, perhaps you can add it to you room in a smaller dose.

    Blue and Green Should Not be Seen

    One of the typical interior design myths, that blue and green should not be seen. When used correctly, the colours are simply stunning together. A deep navy room with a green sofa, or contrastingly, in the room below, a deep green room with a hint of navy, in a simple chair. Note in the picture below, the green colours used are tonal, a darker green wall with a lighter green velvet sofa and rug.

    Simply adding green plants to a navy room will lift the colour.

    Geen and Yellow, a Happy Yet Calming Combination

    Yellow is a colour I’ve had a mixed history with. I have broadly hated it, but that is probably because, previously, I have used rather insipid yellow colours pastels which will never sit in my interior scheme.

    It is now, however, one of my favourite colour combos at the moment (see the corresponding post on my new ochre bed, in my deep green room) a green that will calm and sooth you along with yellow, which is an uplifting colour, a happy vibe. Here, the secret is to use yellow as an accent colour. Think deep green walls with a yellow sofa, or a desk. A velvet green sofa with a yellow throw. An accent chair in yellow. My secret is to keep yellow on the side of mustard and ochre, deep enriching colours that sit well with my dark interiors.

    Yellow sits next to green on the colour wheel and is therefore an analogous colour. These colour sit harmoniously together, creating a pleasing combination.

    Image sources. LHS RHS

    Green and Pink

    A very popular choice in interiors at the moment, and just looking at the photos below, you can see why. Pink and green is a stunning colour combination, arguably a complimentary colour scheme as pink sits on the red end of the spectrum opposite to green on the colour wheel. Complimentary colours will enhance each other. They will appear brighter together than when separately, or one can be used to tone down a deeper shade in the other. Complimentary colours are the simplest to use, typically one colour acts as the dominant colour, with the other in smaller doses. Adding a neutral colour, gives your eye somewhere to rest in most of the images below, wood or brass are providing this effect. In one or two photos, a simple white table or the white of the marble fireplace breaks up the scheme.

    Image Source. Devol Kitchens

    Image Sources:

    Green on Green or in a Neutral Scheme

    If you don’t want to embrace deep green walls, or a mix of green and another colour, try adding a touch of green to a neutral scheme. In the picture from Artist Residence below, green velvet chairs enhance an otherwise neutral room. In the kitchen below, green is used more substantially, but against black and white and with metals and wood to balance it.

    Image Sources: LSH Artist Residence. RHS

    Hints of Green

    And, if you really are not a colour lover at all, you can’t go far wrong with plants and foliage for adding a hint of green to you home. Plants not only look great, but have air cleaning properties. You can read all about the enhancing properties of plants here.

    Flowers on a summer table, or greenery at Christmas, really help enhance a neutral room.

    For me, green is a relaxing colour in my bedroom and a thinking colour in my study. But most of all I simply love the dark hues on the green spectrum. That is what makes my heart sing when I walk through the door.

    Why don't plants absorb green light?

    Do I really need to provide a source to convince you that plants are green?

    It's the rule. Please provide a source that explains your OP. Not everyone that reads these threads can read your mind.

    And by posting a source for your question, you would also find an answer, which is another good reason to flesh out your question with a preliminary search.

    We see because of light bouncing off things and getting into our eyes, the colour that bounces off is what it looks like. Chlorophyll looks green because it stores the red and blue light and bounces off the green and yellow light which go to our eyes. However this doesn’t make much sense – most of the light from the sun is yellow and green! So plants aren’t even touching most of the light they receive.

    It is a question, are questions forbidden?

    It is difficult to find peer review stuff on such an obvious fact, ie that plants absorb red and blue, but not green light.

    It is not the kind of thing which will win you the Nobel prize for biology.

    It is a question, are questions forbidden?

    It is difficult to find peer review stuff on such an obvious fact, ie that plants absorb red and blue, but not green light.

    It is not the kind of thing which will win you the Nobel prize for biology.

    For the sake of people that don't know what you are missing that prompted the question (especially when it's something taught in elementary school), you need to show a source so we can figure out where you are confused or not understanding. Anyway, I posted a very simple explanation for you above.

    In other words, it's for everyone's benefit.

    Evo, I think you are being a bit hard on Joe, even if he does put his questions in a rather awkward way.

    Assuming the question translated is:

    Why do plants reflect the most abundant wavelengths (green/yellow) rather than use them for photosynthesis?

    I thought this a very good question was motivated by this question to trawl the net since I don't know the answer either.

    Firstly a search of PF itself didn't yield an answer.

    Secondly I could cetainly find plenty of people asking this question on the net, but couldn't see one satisfactory answer, although one smart alec offered to email the 'true' answer if you emailed your attempt.

    I found plenty of references to other potential chemical systems using other molecules, including one which used hydrogen sulphide not water as the mediator. This system is chemically favourable over chlorophyll/water and fors the basis of the purple planet theory.

    Fourthly, I found plenty of references to the 'purple planet theory' that early organisms used anaerobic chemistry to photosythesise.

    So I too would be pleased if some knowledgeable member would explain.

    Evo, I think you are being a bit hard on Joe, even if he does put his questions in a rather awkward way.

    Assuming the question translated is:

    Why do plants reflect the most abundant wavelengths (green/yellow) rather than use them for photosynthesis?

    I thought this a very good question was motivated by this question to trawl the net since I don't know the answer either.

    Firstly a search of PF itself didn't yield an answer.

    Secondly I could cetainly find plenty of people asking this question on the net, but couldn't see one satisfactory answer, although one smart alec offered to email the 'true' answer if you emailed your attempt.

    I found plenty of references to other potential chemical systems using other molecules, including one which used hydrogen sulphide not water as the mediator. This system is chemically favourable over chlorophyll/water and fors the basis of the purple planet theory.

    Fourthly, I found plenty of references to the 'purple planet theory' that early organisms used anaerobic chemistry to photosythesise.

    So I too would be pleased if some knowledgeable member would explain.

    Firstly - it's the forum rules which Joe chooses not to follow.

    Secondly - I posted an answer. It took me .05 seconds to pull it up in a google search. There was also an answer from a scientist at argonne, but it didn't go into as much detail.

    Asking questions is fine, but an effort should be made to provide some thought or background along with it.

    Why Is the Ocean Different Colors in Different Places?

    Someone gazing out at the ocean from the Maine coast sees very different hues than someone squinting at the sea from a sunny beach on a Greek island. So why does the ocean come in so many shades of blue?

    First of all, as NASA oceanographer Gene Carl Feldman points out, "The water of the ocean is not blue, it's clear. The color of the ocean surface for the most part is based on depth, what's in it and what's below it."

    A glass of water will, of course, appear clear as visible light passes through it with little to no obstruction. But if a body of water is deep enough that light isn't reflected off the bottom, it appears blue. Basic physics explains why: Light from the sun is made up of a spectrum of different wavelengths. The longer wavelengths appear to our eyes as the reds and oranges, while the shorter ones appear blue and green. When the sun's light strikes the ocean, it interacts with water molecules and can be absorbed or scattered. If nothing is in the water except water molecules, light of shorter wavelengths is more likely to hit something and scatter, making the ocean appear blue. The longer, red portions of sunlight, meanwhile, are absorbed near the surface.

    Depth and the ocean bottom also influence whether the surface appears a dusky dark blue, as in parts of the Atlantic, or casts a sapphire-like shimmer as in tropical locations. "In Greece, the water is this beautiful turquoise color because the bottom is either white sand or white rocks," Feldman explains. "What happens is the light comes down and blue light gets down, hits the bottom and then reflects back up so you make this beautiful light blue color in the water."

    Color Reflects Ocean Health

    And then there's the fact that the ocean is rarely clear, but is instead teeming with tiny plant and animal life or filled with suspended sediment or contaminants. Oceanographers monitor the ocean's color as doctors read the vital signs of their patients. Color seen on the ocean's surface reflect what's going on in its vast depths.

    Feldman, who's based at the NASA Goddard Space Flight Center in Maryland, studies images taken by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite, launched in 1997. From its perch, more than 400 miles (644 kilometers) above Earth, the satellite captures Van Gogh-like swirls of the ocean's colors. The patterns are not only mesmerizing, but they also reflect where sediment and runoff may make water appear a dull brown color and where microscopic plants, called phytoplankton, collect in nutrient-rich waters, often tinting it green.

    Phytoplankton use chlorophyll to capture energy from the sun to convert water and carbon dioxide into the organic compounds. Through this process, called photosynthesis, phytoplankton generate about half of the oxygen we breathe. While most phytoplankton give ocean water a green tint, some lend it a yellow, reddish or brown tint, Feldman says.

    Oceans with high concentrations of phytoplankton can appear blue-green to green, depending on the density. Greenish water may not sound appealing, but as Feldman says, "If it weren't for phytoplankton we wouldn't be here." Phytoplankton serve as the base of the food web and primary source of food for zooplankton, which are tiny animals eaten by fish. The fish are then eaten by bigger animals like whales and sharks.

    It's when oceans become polluted with runoff that the amount of phytoplankton can escalate to unhealthy levels. Phytoplankton feed on the pollutants, flourish and die, sinking to the bottom to decompose in a process that depletes oxygen from the water.

    The Climate Change Effect

    Over the past 50 years, ocean zones with depleted oxygen have more than quadrupled to an area roughly the size of the European Union, or 1,728,099 square miles (4,475,755 square kilometers), according to a study published in January 2018 in the journal Science. Part of the cause may be an increase in ocean temperature due to climate change since warmer water supports less oxygen. In coastal areas, phytoplankton blooms are suspected to be the cause. Phytoplankton may serve as the base of the ocean food chain, but as Feldman says, "Too much of a good thing is not a good thing."

    On a map on Feldman's office wall is a marker showing where there is little human interference and ocean water is perhaps the clearest on the planet. In this region, off the coast of Easter Island in the southeast Pacific Ocean, the water is deep and remarkably clear due to its location in the middle of a giant oceanic gyre, or large circular current. Its central location means there is minimal mixing of ocean layers and nutrients aren't pushed up from the deep bottom. The purity of the water here, coupled with its depth make the ocean here appear a deeper indigo than perhaps anywhere else.

    "The light just keeps going down, down, down there's nothing that bounces it back," Feldman says, "Here is the deepest blue you'll ever see."

    A species of bacteria called Synechococcus cyanobacteria has the ability to adjust its color to match different wavelengths of light across the world's oceans. These bacteria harness light to capture carbon dioxide from the air and produce energy. As research published Feb. 12, 2018 in the Proceedings of the National Academy of Sciences showed, the bacteria contain genes that lend them the chameleon-like ability to alter their color in order to survive in waters of any color and to maximize their ability to process the ambient light around them.