Auto = self, Trophic = nutrition. The exact meaning of this word is self-nutrition. Autotrophic nutrition is a process in which the organism produces their food from the simple inorganic materials such as water, carbon dioxide and mineral salts in the presence of sunlight. All the green plants have an autotrophic mode of nutrition.
The autotrophic organisms have a green colored pigment named “chlorophyll” which helps in catching energy from the sun. They make their own food with the help of the water, solar energy, and carbon dioxide by the method of photosynthesis. This results in the making of glucose.
Plants such as blue-green algae and cyanobacteria could be considered as some examples of autotrophic nutrition.
Every living organism wants some kind of energy and nutrient substances to ensure that the life processes run smoothly. Besides, this energy needed is acquired from the food.
Plants are also a part of living things that require some form of energy. They have cells and tissues. They also grow in girth and size. And they are the creators of the ecosystem. So, in order to create food, they do have nutrient necessities. Of course, the kind of nutrient requirements differs.
This type of nutrition in plants is so-called the “autotrophic mode of nutrition”. What does this actually stand for? It means that plants have the special ability to make their own food, with the help of simple inorganic substances to harvest organic substances. They get energy sources from non-living things like sun and carbon dioxide CO2.
Plants also contain chlorophyll in them, the green color pigment. With the help of all these above elements, plants can yield simple carbohydrates. The carbohydrates thus made are utilized by the plant and gives it energy. When there is a surplus of carbohydrates in the plants, then it is stored as a backup for later use.
According to the kind of energy source used, autotrophic nutrition in plants can be of two kinds. They are Photo-autotrophic nutrition (where sunlight is the energy is the only source) and Chemo-autotrophic nutrition (where chemicals are the energy is the only source).
Plants that can produce their food are called autotrophs. But, there are some plants that cannot and are known as heterotrophs. The method by which plants produce their own food is known as photosynthesis. The photosynthesis process happens mostly in the leaves of the plant which are also known as the ‘kitchen of the plant’. In certain cases, even the stems have the potential to carry out photosynthesis.
Photosynthesis is a method to transform solar energy into chemical energy to produce starch. Different parts of a plant play different roles to complete the photosynthesis.
Leaves – They are the food factories of the plant.
Stomata – It is present in the lower epidermis of the leaf which uses carbon dioxide CO2 from the air.
Roots – They absorb minerals and water from the soil and carry it to different parts of the plant.
Leaves of the vascular plants have a superior structure called chloroplasts which possess chlorophyll. Plants manufacture glucose with the help of carbon dioxide and water in the existence of sunlight. The stomata existing in the leaf releases oxygen and water as a by-product through the daytime. The manufactured food is conveyed to different parts of the plant for storage and utilization. These green plants make proteins using nitrogen which could be acquired from the soil.
All the minerals which are dissolved in water are used to transform sugar into proteins, fats, and carbohydrates. These food constituents act as the source of energy for other heterotrophic animals and plants. Glucose is manufactured by this process and transformed into different compounds like cellulose and starch which is stored in different parts of the plant.
As mentioned earlier, the procedure of photosynthesis happens in the leaf of a plant. The leaf is anatomically separated into many layers. Photosynthesis happens in the mesophyll layer of the leaf, the middle layer also called palisade parenchyma. These mesophyll cells are rich in special cell organelles known as chloroplasts which are responsible for the photosynthesis process.
Leaves also have small openings on their undersurface called ‘stomata’ which are responsible for gaseous exchange and are the source of CO2 that enters the leaf.
These are unique organelles inside which the photosynthesis process occur. Chloroplasts are double-membrane organelles. The Chloroplast contains disc-shaped thylakoids that are arranged together. Stacked thylakoids are known as ‘grana’. It is in the membrane of the thylakoid that pigment chlorophyll is also present.
Photosynthesis process can be separated into two stages:
This reaction is a light-dependent reaction and it is required to generate energy molecules like ATP and NADPH. This reaction happens in the thylakoid membrane of the chloroplast where the sunlight activates of the reaction of chlorophyll pigment.
The stimulated chlorophyll releases an electron which is taken by the H2 of water after its splitting. The reactions that occur are redox reactions and eventually lead to the manufacture of energy molecules- ATP and NADPH which are then required for the subsequent synthesizing reactions that happen in the dark reaction.
This reaction does not literally happen in the dark but is named so because it is independent of light (no light is needed). This reaction can happen both in the presence and absence of sun rays. Due to the scientists who worked to find out this cycle, this reaction is also known as the Calvin- Benson-Bassham cycle.
This reaction happens in the stroma which is present in the chloroplast. This reaction uses the energy molecules produced in the light phase of photosynthesis and transforms CO2 into glucose. The photosynthesis method can be summarized by the following equation:
6CO2 + 6H2O → C6H12O6 + 6O2 (in the presence of sunlight)
Factors Affecting Photosynthesis Process
There are some factors that encourage or inhibit photosynthesis depending on their concentration :
For the plants, photosynthesis helps produce glucose to be able to produce energy to perform other functions such as transport of water and minerals throughout the plant and respiration. Plants require energy also to make other biological and biochemical methods to enable it to multiply. For other organisms, plants serve as food.
The organism that can make their own food with the help of chemical energy and they do not need sunlight. This nutrition can only be possible at night time. Example: Nitrosomonas, hydrogen bacteria, etc.
Sources for Chemoautotrophic Nutrition
Energy Source: Chemicals (Chemo).
Carbon Source: Environmental Carbon Dioxide.
Halophiles (Salt-Loving Bacteria): Halophiles are organisms that thrive in very high salt concentrations. They are a kind of extremophile organism. (The name derives from the Greek word means "salt-loving").
Methanogens (Not to be confused with methanotrophs).
The bacteria and archaea that live in the deep-sea ocean.