Autotrophic Nutrition

Autotrophic nutrition is a type of nutrition wherein an organism synthesises its food. Because of this reason, autotrophs are known as producers. Other organisms obtain their food from these autotrophs. They utilise the available sunlight, carbon dioxide and water and synthesis food through photosynthesis. Hence, the autotrophic nutrition mode is represented by photosynthesis.

The word autotrophic itself means self-nourishing, indicating that these plants directly derive their nourishment from the freely available inorganic matter. All plants are autotrophic, except parasites and saprophytes that depend on other organisms for survival. Autotrophs can fix the energy obtained from the sun into the food chain and act as producers.

Types Of Autotrophic Nutrition

Nutrition is the process of utilising ingested food. The energy obtained from the food is used as the energy source for an organism's metabolic processes. Nutrition includes two types - autotrophic and heterotrophic nutrition. Autotrophs are the name given to organisms with autotrophic nutrition mode. Similarly, heterotrophs are organisms with heterotrophic nutrition modes. Autotrophs can synthesise their food, while heterotrophs don't.

There are two subdivisions of autotrophic nutrition, namely photoautotrophs and chemoautotrophs.

Photoautotrophs

• They have photosynthesis as their mode of food preparation.

• The leaves of plants are the site of photosynthesis. For this reason, stems are referred to as the kitchen of the plant. Sometimes, stems are also involved in the process.

• Leaves possess chloroplast that has chlorophyll, a green pigment that traps sunlight.

• The carbon dioxide gets absorbed through the stomata, a narrow opening present in the epidermis (upper layer of the leaf). The exit of oxygen also happens through the stomata.

• The atmospheric carbon dioxide, sunlight, and water obtained through roots are utilised to produce glucose. It is converted to starch and stored in the plants.

• Oxygen is produced as a byproduct of photosynthesis and is a life-supporting gas.

• About 99% of the energy required for sustaining life comes from photosynthesis.

Chemoautotrophs

• Here, plants produce energy through various chemical processes rather than photosynthesis.

• These chemical reactions usually happen in the absence of light.

• The oxidation of inorganic and organic chemical compounds leads to the production of chemical energy.

• This energy is trapped in the plants as ATP molecules and is used in absorbing carbon dioxide utilising hydrogen from sources other than water. It ensures that no oxygen is involved in the process.

• Chemosynthetic bacteria like Nitrosomonas, nitrifying bacteria, sulphur bacteria, etc., handle the recycling of nutrients like nitrogen, sulphur, and phosphorus.

• Chemosynthetic bacteria can convert the hydrogen sulphide emitted from deep-sea hydrothermal vents, which shows their importance.

• These are believed to be the first of life on Earth.

Working Of Chemosynthetic Bacteria

• Nitrifying bacteria oxidise nitrogen and its compounds to produce energy. It changes the Ammonia to nitrogen dioxide first (Nitrosomonas and Nitrococcus). Then it gets converted to nitrates by Nitrobacter and Nitrocystis.

• Iron bacteria like Ferrobacillus convert the ferrous ions to ferric ions.

• Hydrogen bacteria like Hydrogenomonas convert the entire hydrogen to water.

• Methane bacteria like Methanomonas convert methane molecules to carbon dioxide.

• Sulphur bacteria can be of two types. Some, like Beggiatoa, convert hydrogen sulphide to sulphur, while others, like Thiobacillus and Thiooxidans, convert the sulphur to sulphuric acid.

Examples Of Autotrophic Plants

• Green plants

• Autotrophic bacteria like cyanobacteria

• Diatoms

• Golden algae

• Red algae

• Blue-green algae

• Phytoplankton

• Seaweeds

Nutrition Requirements Of Plants

Plants also have cells and tissues like other living beings and require energy for growth and development. They produce food in the form of carbohydrates (glucose) by photosynthesis to convert simple inorganic substances to organic matter. The energy produced is utilised for various processes, and the excess energy is stored for future use.

Atmospheric factors like light temperature, carbon dioxide, and oxygen affect photosynthesis. The concentration of these factors can affect the rate of photosynthesis. Plants need energy for their biochemical and biological processes. They also act as food for other organisms.

Significance Of Autotrophs

• They are vital to sustaining life on Earth.

• As the name producers indicate, they convert atmospheric carbon dioxide to sugar (glucose).

• They form a food source for all the heterotrophs, like humans and other animals.

• Plants (autotrophs) form the base of food chains and energy pyramids.

• Autotrophs are the first to evolve on Earth. Later, heterotrophs originated from them.

• Higher ecosystems have autotrophs forming their base.