Why Plants Are Green?

Have you ever wondered why plants are green in color? The answer lies in a process of millions of years that continues today and that allows plants to survive and develop.

Elements that cause plants to be green

Undoubtedly, you have heard of photosynthesis and chlorophyll. Chlorophylls are tiny photosynthetic pigments (capable of absorbing light and preparing it for photosynthesis ), located in the chloroplasts, from where they absorb this light. Chloroplasts are oval-shaped organelles, in which chlorophyll is contained, thanks to which photosynthesis can be carried out.


Photosynthesis is a chemical process that transforms inorganic matter into organic matter using the energy of sunlight. This process is carried out as follows: 

  • Plants capture water through their roots and transport it to the leaves through the stem. 
  • On the other hand, they absorb carbon dioxide through pores in their leaves, called stomata
  • This gives rise to a chemical reaction that (thanks to the energy of sunlight) transform water and carbon dioxide into glucose and oxygen, allowing plants to grow and obtain their food.
Photosynthesis equation

So when fall comes and the plants look different colors, is it because they have lost chlorophyll? Absolutely! These tiny particles are simply hidden under other pigments, and that is why, at certain times of the year with fewer hours of sunlight, the landscape is tinged with reddish and yellowish tones.

We already know that chlorophyll is what gives plants their green color. Now, the logical question would be: why does chlorophyll have this color? 


We can say that chlorophyll is the natural dye that makes plants green. It is present in many of the elements of plant organisms, and although it gives them their green hue, in reality, this is not their main purpose.

The objective of chlorophyll is not to color them green to make them beautiful but to better capture light through this color so that they can carry out photosynthesis and thus obtain food.

Why chlorophyll is green and how this color helps photosynthesis in plants

In this case, it is an energy issue. Light is made up of tiny energy particles called photons. The energy of a photon is determined by the frequency of the light: the higher the frequency, the higher the energy. The frequency of blue light is higher than that of red light, so blue photons will have more energy than red ones.

Sunlight is very abundant in photons of red light and to a much lesser extent in photons of blue light. Chlorophyll seeks to capture both the parts of the spectrum that are most abundant and those with the highest energy, so they use an intermediate light spectrum: green. In this way, it seeks to optimize the capture of forms of light from the sun.

Why did green aquatic plants take over the land?

Finally, we only need to know how the plant world managed to reign on the earth’s surface. Simple. As Darwin demonstrated: Evolution and adaptation! Plant life originated in the sea, from where, through the centuries, they would emerge, and conquer the earth’s surface through a slow and long process of adaptation.

Under the sea, there was a multitude of photosynthetic organisms whose pigmentation was different from that of other species since they better captured the ranges of light that penetrated the water. The difference in shades was influenced by some factors such as the degree of filtration of light from the atmosphere or from the water, or the different depths it reaches. Its greater or lesser incidence in the underwater species caused the color differences between them.

But why was it the green algae and not the yellow, red or blue ones that conquered the surface? Well, simply, because the green ones were the best adapted to receive and capture the light that hit them.

In this way, once established on land, photosynthetic organisms that had a green pigmentation were perfectly prepared to obtain the greatest amount of energy possible. Thus they were able to develop, expand and prevail over the other forms of pigmentation, which were not able to adapt to life outside the sea, being forced to remain underwater.

In summary: we already know that the plants that surround us have that characteristic green color because it allows them to better absorb light to carry out photosynthesis.

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