Why are most plants green?

Even a junior high school biology teacher in the nine-year compulsory education system will tell you this:

"Because there's chlorophyll in it, photosynthesis is going to be produced so they can live. ”

This is common sense, from young children as young as five or six years old to middle-aged people as old as forty or fifty years old, they all know about photosynthesis and chlorophyll.

Even if you don't understand the specific principle, you will know that "it is better for plants to bask in the sun, if they don't get sun, they will die", "plants can supply oxygen" and other common sense.

But green plants, especially their green leaves, where chlorophyll is most abundant, have a huge drawback.

Plants are green because they reflect the green light in the sun's rays, in other words, they don't absorb green light.

However, one of the paradoxical things is that in the spectrum of sunlight, green light is the most abundant photon.

So why is this most abundant resource being abandoned by hundreds of millions of photosynthesizers who depend on sunlight, and why do plants do such contradictory things?

The answer to this question may lead to an epic war, but it is also even more shocking - perhaps the original plants are not green, everything is the imprint of billions of years of evolution of life.

The origin of the organism comes from two cells that overflowed from a hydrothermal vent of the deep sea, and these two cells quickly multiplied into the two most primitive families of the biological world, which are eubacteria and archaea.

They are the earliest creatures, and naturally they also have a biological instinct, "movement".

They follow the currents, carrying the seeds of life wherever they can live, and the first step out of this hot spring and into the wider world.

Unfortunately, freedom is not free.

To be free from the warm hotbed of life in the deep-sea hydrothermal vent is to be detached from the endless supply of energy and material in the hot spring.

The matter is not particularly barren, and there are still a lot of stocks of carbon dioxide, hydrogen sulfide and methane needed to synthesize living matter in the ancient earth's oceans. But the energy provided by the volcano cannot be taken away.

So, in order to reproduce and survive, perhaps it is their self-awakening, or perhaps it is the impetus of some evolutionary hand in the dark, a more inexhaustible energy source has come to these ancient beings.

Sun.

During the long evolution, one cell accidentally synthesized a special molecule, retinaldehyde.

With the help of this molecule, archaea can use the sun's light energy to maintain the alkalinity in their cells, so that a certain pH difference is always maintained inside and outside the cell membrane, so that it can mimic the delicate acid-base neutralization reaction in the deep-sea hot vent to provide energy for cell activities.

In fact, the human eye relies on retinaldehyde, using a similar principle to convert light into god-level signals.

And in that ancient desolate world, whoever embraces the sun's rays first is equivalent to embracing everything.

So this life, of course, directly and rapidly expanded to the whole world.

However, this pioneer who was the first to embrace the light had nothing to do with what we call plants today, and their principles of using sunlight were very different from what is called photosynthesis today.

They weren't the plants they are today, they were a group of archaea to be exact.

They're not green either. Because retinaldehyde strongly absorbs the most abundant green spectrum of sunlight, these archaea exhibit the most vivid purple color.

Three billion years ago, the earth was a purple world rendered by archaea.

The oceans, rivers, tidal flats, everywhere life can stand, are covered with a thick purple fungus blanket, bringing the first vitality to the scorched earth where there is no oxygen and hydrogen sulfide everywhere.

However, this is not an idyll of life, and under this thick fungus blanket, there is another force that is quietly accumulating strength.

They are another offspring that came out of the deep-sea hydrothermal vent back then, true bacteria.

Eubacteria naturally want to use light energy, but the energy from the sun is stripped by the purple archaea, and only an insignificant amount is left to the bottom of the fungus blanket.

These eubacteria can only find hope of survival from the residue of light energy, so they choose another small molecule called "porphyrin", which is almost completely unable to absorb green light, so it is easy to appear blue-green.

But they can extract the last trace of light energy left under the blanket.

But energy alone is not enough, life also needs matter.

Most early life also learned to use solar energy to disassemble hydrogen atoms from hydrogen sulfide and give them to carbon dioxide to make organic matter.

Although hydrogen sulfide was everywhere on the earth at that time, it was also difficult for the true bacteria that oppressed under the fungus blanket.

Maybe taking a step back, it's genocide.

Hundreds of millions of years of struggle, like the king of Yue, Gou Jian, lying on his back and tasting his courage, finally quenched a magical bacteria, their names can be said to be thunderous to this day-

Cyanobacteria.

These bacteria have developed an extremely complex photosynthetic system that allows them to use a molecule that no other organism can use: water.

They rely on the very few photons that pass through the blanket to accumulate energy and split the water molecules, from which they take the hydrogen atoms necessary for the synthesis of organic matter.

True photosynthesis has since come to the stage of history.

At the same time, a devastating apocalyptic battle has begun.

It is oxygen that is left behind after the water molecule has been seized of the hydrogen atom.

At first, there was nothing wrong with that, as the ubiquitous ferrous ions, hydrogen sulfide, and so on on the earth would quickly absorb any oxygen molecules on the surface.

However, under the blanket of purple mushrooms, countless cyanobacteria are working day and night to draw energy and produce oxygen from the sunlight that shines through.

This difficult photosynthesis lasted for a billion years, and the saturation of oxygen for a billion years finally exhausted all the reducing power of the earth's surface.

Almost every ferrous ion in the ocean was oxidized into rust and deposited on the ocean floor, forming the "banded iron layer" in today's strata.

Almost every hydrogen sulfide molecule in the air is oxidized and settles to the ground with rainwater, forming sulfate deposits.

Twenty billion years ago, when free oxygen finally appeared in the atmosphere, a revolution that overturned an old world began, and later generations called this revolution the "Great Oxidation Event"!

The oxygen is permeated, like a scythe-armed Grim Reaper transiting, and in the face of Death, no one is exempt.

Whether it's purple or green, all beings are equal.

Oxygen itself is the great enemy of life, because oxygen will indiscriminately oxidize to form the material basis of life, organic matter.

But that's just the beginning.

Oxygen also destroys methane, a greenhouse gas more than 20 times more potent than carbon dioxide, at a time when the planet's volcanic activity was at a low point.

As a result, the Earth's temperature plummeted, and the Ice Age entered the most violent global cooling since the birth of the Earth.

The extremely cold ice freezes and freezes, and after all, all the disturbances in the world have been extinguished.

In the battle of the end of the world, there is no winner.

The once-spectacular fungus carpet has been buried deep underground, and after billions of years of geological changes, it has evolved into a fossil called a cascading stone, like a tombstone, silently paying tribute to the purple dynasty that once belonged to them.

It's just that life will always find a way out, and in this catastrophe that spanned hundreds of millions of years, some bacteria finally adapted to the oxygen-like environment, and even unlocked the ability to aerobic respiration.

They may have curled up near the mouth of the icy hot vent of the deep sea, saving the only remaining bonfire.

After 300 million years of slow ice, the glaciers of the Ice Age finally melted, and the warm sunlight once again sprinkled on the green carpet of cyanobacteria.

In this new era of oxygen, there will never be any purple archaea competing with them for light energy again.

It's a pity that their photosynthesis system with "porphyrin" as the core has evolved for more than a billion years in that world where green light is monopolized, and it has long been difficult to return.

The resulting photosynthetic systems are incapable of using green light from the underlying architecture, and their descendants eventually leave behind a counter-intuitive green world today.

But they do much more than that, and aerobic respiration brings more energy to life than ever before.

On this basis, complex cells and even multicellular organisms are finally possible.

What's more, the Earth's atmosphere was once completely powerless to block ultraviolet light, which could have broken down water into hydrogen and oxygen, and the Earth's gravitational pull could not bind hydrogen.

Therefore, if the ultraviolet rays continue to bombard, the earth will one day lose all its water.

However, the increasing concentration of oxygen eventually built a barrier called the ozone layer above the earth, ending this process in one fell swoop and providing a solid protection for life on the earth.

"The rudiments of today's world. Wu Peng said slowly.

Ouyang was stunned for a moment, as if he had a dream that spanned hundreds of millions of years, and he didn't know what the situation was for a while.

At this time, the mecha on his body had disappeared, replaced by the modern outfit he had just entered the world, a suit full of pockets.

And unsurprisingly, Deochisis really went offline again.

"What's the situation...... Did I read a chronicle of the earth?" Ouyang couldn't help but sigh.

He didn't ask, but let out an exclamation, which came from his unrecoiled brain, and his consciousness was slightly sluggish as if it had just been restarted.

The Wu Peng in front of her is no longer a twisted tree man, or a plant brain, she is exactly the same as the Wu Peng Ouyang saw in the Yellow Emperor era, with a petite body and a pale yellow robe, she is a real "witch".

"Pretty much. Wu Peng looked at Ouyang with burning eyes and showed a bright smile, "Long time no see, Your Excellency Ouyang." ”