photosynthesis in plants

Do you believe us if we say that plants are not the only organisms that carry out photosynthesis? It sounds incredible, but it is true, not only plants are capable of carrying out a photosynthetic process. A salamander, corals, some algae and a couple of cyanobacteria are the characters in the play today.

Photosynthesis

To begin with, do you know clearly what photosynthesis is? This is the means to manufacture a substance and an element: sugar and oxygen. As? With two natural resources: water and sunlight. Plants, algae and cyanobacteria are capable of carrying out this process . This occurs through a long series of chemical reactions. But it can be summed up as follows: Carbon dioxide, water and light enter. Glucose (which is a simple sugar), water, and oxygen come out. Easy right?

But we will explain it better. Photosynthesis can be divided into two processes. The process of the “photo” refers to the responses that are generated by contact with light. The “ synthesis ” part – which is the manufacture of sugar – is a separate process called the Calvin cycle. Both processes take place within a chloroplast, which is an elementary structure of a plant cell. This structure contains stacks of membranes called thylakoid membranes. This is where the light begins to react.

oxygenic photosynthesis

Now, how is it that not only plants carry out photosynthesis, but chloroplasts and many other elements are needed? There are two explanations, the first very scientific: there are two types of photosynthesis, oxygenic and anoxygenic. The second, very colloquial : there are organisms that do not produce photosynthesis, but are experts in stealing what produces it: chloroplasts. We’ll explain it.

Organisms that perform oxygenic photosynthesis (which produces oxygen) are plants, cyanobacteria, and algae. With this there is something fabulous, there are organisms that can carry out a type of symbiosis or “theft” of chloroplasts from certain algae and benefit from their photosynthesis process. This is what is known as kleptoplasty and animals such as the sea slug Elysia diomedea and the spotted salamander Ambystima maculatum are well aware of this.

the spotted salamander

The case of the salamander is extremely exceptional: it is classified as “the first vertebrate animal to make use of photosynthesis”. You have to give credit to the salamander, it’s not so much that she is an expert in stealing chloroplasts and is looking to be the Robin Hood of the jungle, no.

It’s more that when the salamander hatches its eggs, that is, lays them, a bunch of algae come to live in them and something called mutualism happens. This mutualism, in simple words, works when two organisms benefit each other. In this case the eggs serve as a home for the algae and the algae provide the eggs with oxygen (this is known as mutualistic symbiosis). Beautiful isn’t it?

sea ​​slug

The Elysia cholorotica is a leaf-shaped mollusk that, apparently, is one of those who are not satisfied with the life they have and want that of others. To say this, we base ourselves on the few studies that have been done on this organism that, like many humans, only wants to live off the air, only that it does so on the sun. Yes, Elysia cholorotica goes through life eating algae that allows it to feed on sunlight. The characteristic green color of this sea slug is obtained precisely from the algae it eats.

The corals

On the other hand, there are other organisms such as corals, which are the owners of the business and, instead of stealing chloroplasts from the algae, they kidnap the algae. Some bosses in the matter. Between algae and corals there is also mutualistic symbiosis. In this case, the corals are the refuge of the algae because nobody else eats it, except the coral, which uses the algae as food.

anoxygenic photosynthesis

Finally, there are the organisms that carry out anoxygenic photosynthesis (which does not produce oxygen) which are the purple or red photosynthetic bacteria and the green bacteria, known as cyanobacteria.

What these bacteria do is not far from equally fabulous. Like plants, photosynthetic bacteria use solar energy to grow healthy and strong, but they have simpler structures and can grow even in laboratories. Not by themselves, but at the hands of researchers eager to learn more about cyanobacteria, cataloged as responsible for the evolution of life on earth that it has.

Photosynthetic organisms and the cellulose biopolymer.

Not only the mentioned organisms take advantage of or benefit from photosynthetic organisms. Humans do too. Photosynthetic organisms, such as plants, algae, and some bacteria , produce more than 180 billion tons of organic matter each year. This comes from the fixation of carbon dioxide. Half of this organic matter is made up of carbohydrate macromolecules known as cellulose biopolymers, the same that makes up the entire internal structure of the cells of a large number of plants.

Cellulose is also an important component of wood, as well as cotton and other textile fibers such as flax, hemp, and jute (ramie). For this reason, cellulose has always played an important role in human life. Furthermore, its applications may even be a milestone in the understanding of human evolution.

Fine linen and raw cotton have been found in the tombs of the Egyptian pharaohs. However, it was in the early dynasties in China that the first ways to create cellulose substrates used for writing and printing were put to the test. Exploration, trade and battle have depended for many centuries on man’s ability to build wooden ships, make sails from cotton and rope from hemp.

Until the beginning of the 20th century, cellulose and other biomacromolecules extracted from renewable resources were the raw materials for the production of fuels, chemicals, and materials. Little by little they were replaced by petroleum derivatives. The depletion of oil resources, as well as the current concern about global warming, have motivated the change from dependence on fossil resources to renewable biomass resources. This, both in terms of energy production and basic products. Which is why photosynthesis and photosynthetic organisms (such as plants) are so important to human and environmental life.

Sources

• Alonso, J. (2013). Photosynthesis and Animals .
• Archibald, J. (2014). One Plus One Equals One: Symbiosis and the evolution of complex. Reviewed by Luis Alonso in Simbiosis : A revolutionary perspective of life and its history.
• Khan Academy. (nd). Light-dependent reactions .
• Aquae Foundation. (2021). Do you know how PHOTOSYNTHESIS works ? Youtube video
• Main, D. (2018). The secrets of slugs that “steal” chloroplasts from algae .
• Martínez, C. and López, A. (2018). Cellulose: Fiber and Energy. Plants and biomass .
• UCC+i. (2019). ‘ Cyanobacteria’ , the photosynthetic bacteria that invented the world.