Nutrition In Plants
Science Class Seven
Saprophytes
There are many organisms which grow on decaying plants and animals. They feed on those dead decaying plants and animals.
Organisms which grow and feed on dead decaying plants and animals are called Saprophytes. And this mode of nutrition is known as Saprophytic Mode of Nutrition. For example bacteria and fungi. Mushroom is one of the most common examples of saprophyte.
Most baceria and fungi get their food from dead and decaying plants and animals. They release enzymes to break down complex organic matter into simple ones which are then absorbed by them. Example: Agaricus (Mushroom), yeast and bacteria. They are known as Saprophytes.
Some fluffy umbrella-like patches growing on rotting wood during the rainy season can be seen easily. Or small umbrella like structure selling on the vegetable market is common. This is called Mushroom. Mushroom is a fungi. Some mushrooms are eaten as vegetable. Mushroom grows on decaying wood or hay. As Mushroom is a fungi so it does not prepare food by the process of photosynthesis.
Such fungus depends for food on those decaying places, where it grows. It releases enzymes to break down complex organic matter into simple ones which are then absorbed by it.
Some white fluffy cotton like patches appears on pickles or on the piece of bread, which is left for more days unused in kitchen. These patches may be of white, green, and brown or of any other colour. This is called fungus. They get feed in the same way as mushroom.
Fungi also grow on pickles, leather, clothes and other articles that are left in hot and humid weather for long time.
Using of Fertilizer
Fertilizers are used to enrich the fertility of soil. Plants get their nutrients other than carbohydrate from the soil. So gradually the amount of nutrients decreases in soil. The less amount of nutrients in soil resulting as less fertility and less yield.
To fulfill the nutrients, fertilizers which contain nitrogen, potassium, phosphorus etc. are needed to be added time to time to the soil. Adding of fertilisers maintain the level of essential nutrients. So that yield of crops would be better.
Usually crops require a lot of nitrogen to make proteins. After the harvest, the soil becomes deficient in nitrogen. Nitrogen is available in plenty in the gaseous form in the air. But plants do not take nitrogen from the air. Plants need nitrogen in the soluble form. And plants absorb nitrogen from soil. Urea is a nitrogen rich fertilizer. Farmers usually add urea after harvesting to make the soil nitrogen rich.
Soil is tested time to time to find the deficiency of nutrients if any. Accordingly fertilizers are added to the soil to fulfill the deficient nutrients.
How Nutrients are Replenished in the Soil
Bacteria are microorganisms and fix nitrogen in soil. These bacteria are called diazotrophs. Some higher plants, and some animals (termites), have formed associations (symbioses) with diazotroph. Example - Cyanobacteria, Azotobacteraceae, Rhizobia, Frankia are the microorganism that are referred as diazotrophs because they are able to fix nitrogen in the soil.
Rhizobium is a kind of bacteria, take nitrogen from the atmosphere and convert it into soluble form. This soluble form of nitrogen is absorbed by the plants from the soil. This rhizobium is referred as Diazotrophs.
Rhizobium also shows the Symbiotic Relationship with the pulse crops. As Rhizobium cannot make its own food, it lives in the roots of gram, peas, moong, beans and other legumes. Rhizobium absorbs nitrogen from the atmosphere and converts it into the soluble form. The soluble form of nitrogen is used by the crops of pulses. In return, the plants provide food and shelter to the bacteria. This type of relationship is known as symbiotic relationship. This association is of great significance for the farmers.
Some plants are known as nitrogen fixing plants and are called leguminous plants. Leguminous plants absorb soluble form of nitrogen from soil, which is converted by the bacteria lives in their roots. These plants release the nitrogen again to the soil after decaying. So, farmers do not need to add nitrogen fertilizer to the soil in which leguminous plants are grown.
Summary of Nutrition in Plants
(a) Plant is essential for life. Without plants life is not possible on earth.
(b) Plants are the only organism on the earth which prepare their food for themselves. Animals cannot make their food themselves.
(c) Animals including human either eat the plants or the products of plants, like rice, wheat, pulse, vegetables etc. or they eat animals like meat of animals such as fish, goat, deer, rabbit etc, which eat plants.
(d) Thus, animals including humans are directly or indirectly dependent on plants.
(e) Nutrition – The mode of taking food by an organism and its utilization by the body is called Nutrition.
(f) Nutrients – The components of food are called nutrients.
(g) Green plant converts the simple substances; Carbon dioxide and water into food in the presence of sunlight by the process of photosynthesis.
(h) Autotrophs – Organisms, which make their food themselves are called Autotrophs (Auto – Self; Trophos – nourishment). The mode of making food for them is called autotrophic nutrition. So, green plants are called autorophs, as they can make their food themselves.
(i) Heterotrophs – (Heteros – other; trophos – nourishment) – Organisms which do not make their food themselves and depended on food made by plants, are called Heterotrophs. This mode of nutrition is called heterotrophic mode of nutrition. So, Animals and most other organisms take readymade food prepared by the plants and are called Heterotrophs.
(j) Non-green plants do not have chlorophyll present in them and thus do able to make food by the process of photosynthesis, and hence depend on the green plants. These type of plants which feed on other plants are called Parasites.
(k) Symbiotic Relation – If two organisms live together and help each other is called Symbiotic Relationship.
(l) Insectivorous Plant – Some plants feed on small insects and have developed special mechanism to capture their prey for food are called Insectivores plants. These are also referred as Carnivores plants.
(m) Saprophytes – Most baceria and fungi get their food from dead and decaying plants and animals. These are referred as Saprophytes.
(n) Photosynthesis – The process of food making by plants in the presence of sunlight is called photosynthesis.
(o) Photosynthesis is a Greek word. ?Photo? is stands for ?light? and ?synthesis? is ?putting together? or ?to prepare?.
(p) The organisms that make their food by the process of photosynthesis are called ?Photoautotrophs?, since they can create their own food using sunlight.
(q) For the process of photosynthesis presence of chlorophyll, sunlight, carbon dioxide and water are necessary. In the absence of any one of these, photosynthesis would not be taken place.
(r) Significance of the photosynthesis:
Photosynthesis is the primary source of food for all living organism. As animals are depend directly or indirectly on the plants.
In the process of photosynthesis, Carbon dioxide which is released in the process of respiration, and is dangerous for animals is absorbed by the plants.
Oxygen which is released in the process of photosynthesis is necessary for the plants and animals to live.
This process of absorption of carbon dioxide and release of oxygen maintains the level of both of the gases in the atmosphere.
(s) Bacteria are microorganisms and fix nitrogen in soil are called Diazotrophs. These are also termed as nitrogen fixing organism.
(t) Some plants are known as nitrogen fixing plants and are called leguminous plants.
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