Photosynthesis

  • Photosynthesis: plants produce organic substances from carbon dioxide and light energy.
  • To achieve it, plants use organs found in plant cells, called chloroplasts, which contain a pigment known as chlorophyll that gives plants their characteristic green color.
  • The chlorophyll in the chloroplasts allows light to be trapped (they capture sunlight), which, combined with the carbon dioxide absorbed by the plant’s stomata, helps transform the raw sap into processed sap.
  • During photosynthesis, the plant splits water molecules absorbed from the soil into hydrogen and oxygen.
  • During photosynthesis, plants use light energy to produce glucose from simple inorganic molecules (carbon dioxide and water).

Everyone has heard the concept of photosynthesis.

Why? Because it is one of the main processes that allow living things to exist on planet earth.

Plants, unlike animals, can produce their food.

They achieve this thanks to a process known as photosynthesis, in which plants produce organic substances from carbon dioxide and light energy.

This process also allows them to grow and develop and to generate oxygen. Thus, photosynthesis is, in all probability, the most relevant chemical process on Earth, since, without it,  life on our planet would not be possible .

But let’s talk in more detail about photosynthesis and what it consists of to understand why it is so important.

What is photosynthesis?

Photosynthesis is the process that all plants, trees, algae and some bacteria carry out to feed themselves.
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How do plants accomplish this process?

To achieve it, plants use organs found in plant cells, called chloroplasts, which contain a pigment known as chlorophyll that gives plants their characteristic green color.

It also helps them capture light energy to transform it into chemical energy.

The pigment called chlorophyll is green. This causes the leaves of plants to have a green color generally.

During this process, gaseous oxygen is generated and released into the environment.

For what is photosynthesis?

As we have already seen, photosynthesis serves, in principle,  for plants to feed themselves,  by synthesizing organic matter from light energy.

Thanks to this process, plants provide oxygen and renew the air, eliminating carbon dioxide or CO2.

How and where does it take place?

The photosynthesis process, which is how plants obtain energy, is  divided into four main stages :

Absorption: Roots absorb water and minerals from the soil.

Circulation: Nutrients circulate from the roots to the leaves through the stem.

Photosynthesis takes place in the leaves, which are oriented towards the light to carry it out. The chlorophyll in the chloroplasts allows light to be trapped (they capture sunlight), which, combined with the carbon dioxide absorbed by the plant’s stomata, helps transform the raw sap into processed sap.

Feeding: oxygen does produce during the process, which does expel by the leaves. Oxygen is equivalent to post-feeding waste. It is here that electron chain transport and carbon dioxide fixation occurs.

Respiration: This process occurs both during the day and at night. During the day, with the presence of sunlight, the leaves photosynthesize and release oxygen. At night, with no light to absorb, plants are limited to respiration only.

 There are several essential factors  that contribute to photosynthesis. Let’s make a detailed explanation of each of them.

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What components does photosynthesis need to develop?

Here are the elements required for photosynthesis to take place correctly:

Light intensity.

Without light, plants cannot photosynthesize, even if there is enough water and carbon dioxide in the environment.

If the light is scarce, photosynthesis proceeds more slowly.

Carbon dioxide concentration

Carbon dioxide is a necessary reactant for the process to occur.

Water

During photosynthesis, the plant splits water molecules absorbed from the soil into hydrogen and oxygen. As a result of this reaction, oxygen is released into the environment, while hydrogen does use in other processes.

During photosynthesis, carbon dioxide combines with the released hydrogen, and together they form glucose.

The chemical reactions that combine carbon dioxide and water to produce glucose do control by enzymes, which brings us to the fourth determining factor.

Temperature

All enzyme-controlled reactions are affected by temperature.

At low temperatures, the rate of photosynthesis does limit by the number of molecular collisions between enzymes and substrates.

At high temperatures, enzymes do denature, which means that their structure and functions do alter.

Chlorophyll quantity

 Chlorophyll is indispensable for absorbing the light energy  required to convert carbon dioxide and water into glucose.

Leaves that contain more chlorophyll are better able to absorb light.

Plants in poor lighting conditions synthesize more chlorophyll to absorb the amount of light they require.

Some plant diseases can affect the amount of chlorophyll and, therefore, their ability to photosynthesize.

Minerals and nutrients

Last but not least, successful photosynthesis requires healthy plants.

This is achieved through the intervention of certain minerals and nutrients necessary for healthy plant growth.

Nitrogen, sulfate, phosphate, iron, magnesium, calcium, and potassium are required in substantial amounts to synthesize amino acids, proteins, coenzymes, deoxyribonucleic acid (DNA), and ribonucleic acid (RNA), chlorophyll, and other pigments.

Other elements such as manganese, copper, and chloride are also necessary for photosynthesis. Likewise, some other trace elements do need various non-photosynthetic functions in plants.

How is photosynthesis initiated?

Light is composed of photons. The chloroplasts capture the photons thanks to the chlorophyll they contain.

At the same time, the plant feeds itself through the roots. They absorb water and minerals that travel through the stem.

From the environment, plants absorb carbon dioxide.

The light absorbed by the chloroplasts helps the plant to split water molecules easily.

Hydrogen forms glucose from this splitting, which transforms into other organic compounds such as sucrose, starch, lipids, proteins, and cellulose.

Oxygen is discarded and is what we end up breathing.

In addition, during the process, a fundamental molecule for living organisms is synthesized: ATP or Adenosine Triphosphate, which is the primary source of energy for living beings.

Why is it important?

Thanks to photosynthesis,  humans obtain most of the oxygen  we need to breathe. We, in turn, exhale carbon dioxide, which plants need.

In addition, humans need all kinds of plants for food.

Other important contributions of photosynthesis:

Photosynthesis makes it possible to produce organic matter from inorganic matter. Then, this organic matter will be processed and transmitted from one living being to another through the trophic chains.

Photosynthesis is fundamental to transforming the primitive and anaerobic atmosphere into an anaerobic atmosphere.

The energy stored in fossil fuels such as coal, oil, and natural gas depends on photosynthesis.

Plant products such as wood, rubber, grasses, medicines, resin, and oils are derived from photosynthesis.

Photosynthesis contributes to the necessary balance between autotrophs and heterotrophs.

Thanks to photosynthesis, CO2 produced by animals and decay processes can be reused and synthesized. Otherwise, CO2 or carbon dioxide would saturate the planet, which would have fatal consequences for life on the earth.

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How does photosynthesis produce energy?

During photosynthesis, plants use light energy to produce glucose from simple inorganic molecules (carbon dioxide and water).
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Similarly, this reaction can do used to generate alternative fuels. This reaction may be possible by exploiting the splitting of water molecules into hydrogen and oxygen.

The combustion of molecular hydrogen, H2, with oxygen produces heat, water, and moisture.

Once obtained, hydrogen could also do used to obtain methanol, a viable substitute for petroleum.

Who discovered photosynthesis? A bit of history…

The first recorded hypothesis about photosynthesis dates back to Ancient Greece. It belongs to Aristotle, who suggested that sunlight was somehow closely related to the green color of plants. However, he eventually forgot his theory.

Later, Empedocles of Agrigento, another famous Greek philosopher, proposed that plants fed on air, which they assimilated through some internal process.

His theory would be refuted, paradoxically, by Aristotle himself and by one of his disciples, the native of Eresus, Tirtamus, better known as Theophrastus, who maintained that all plant food was derived from the air, which plants assimilated through some kind of internal process.

It was not until the 17th century that the English clergyman Stephen Hales, considered by all to be the father of plant physiology, took up both theories in his work published in 1727, Statique des végétaux. In this study, Hales made the first records of the movement of water in plants and succeeded in demonstrating that they used the air that penetrated the leaves of plants as a source of food.

Stephen Hales’ studies influenced another English clergyman, Joseph Priestley, who is credited with the discovery of oxygen and who claimed, among other things, that oxygen was produced by plants by a process the reverse of animal respiration.

To arrive at these conclusions, Priestley based himself on an experiment with a candle, which he had placed in a closed container and burned until the container could no longer support combustion. He then placed a sprig of peppermint in the vessel. He found that, after several days, the peppermint had produced some substance that enabled the air confined in the boat to support combustion again.

Such a substance, it turned out, was oxygen.

In 1779, the Dutch physician Jan Ingenhousz expanded on Priestley’s work, demonstrating that the plant had to be exposed to light to produce oxygen. He also showed that this process required the presence of the plant’s green tissues.

Strictly speaking, Ingenhousz, based on all the previous studies, made the greatest advances in demonstrating the process of photosynthesis in plants. It was based on his studies that later scientists were able to extend this knowledge.

Years later, German professor Ferdinand Gustav Gustav Julius von Sachs would discover chloroplasts and develop a basic equation to represent photosynthesis.

Can houseplants photosynthesize?

As we have explained, if plants primarily need sunlight to photosynthesize, how can houseplants carry out photosynthesis?

This is because houseplants do not need direct sunlight. They only need a few hours of daylight (through a window, for example) to carry out this process correctly.

Many of them benefit from not being exposed to direct sunlight, especially during the warmer months.

Bibliography and references

Book: The Mechanism of Photosynthesis, by Charles Percival Whittingham (1976).

Book: Manual de Practicas de Fotosintesis, by Rosa Rodés García, Collazo Ortega, Margarita (2006).

Book: Bioquímica de los microorganismos, Ramon Parés i Farràs, Antonio Juárez Giménez (1997).

Book: Biology: Concepts and Relationships, Neil A. Campbell (2001).

Article: Conceptual errors in biology. The photosynthesis of green plants. H Astudillo Pombo, A Gené – Enseñanza de las Ciencias, 1984 – ddd.uab.cat

Article: Photosynthetic pigments, more than just capturing light for photosynthesis. EM Reol – Ecosystems Magazine, 2003.

Article: Photosynthesis, photoprotection, productivity and abiotic stress: some case studies by Tambussi, Eduardo Alberto (2005).

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Sobre el autor

Soy Carolina. Cursé estudios de el Grado en Ingeniería Agrícola por la Universidad de La Rioja.

Desde siempre, me ha gustado redactar, editar y publicar información relacionada con el medio ambiente, la agricultura, la jardinería y el cultivo de frutas y hortalizas.

En Sembrar100 puedo llevar a cabo esta tarea, y la verdad: ¡Me encanta!

Mi labor como editora jefe me lleva bastante trabajo, puesto que además de redactar, debo revisar y corregir fuentes bibliográficas, así como posibles erratas que podamos cometer.

Espero que la información que aquí ofrecemos te guste 🙂