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Chapter 1 Nutrition In Plants Class 7 Science Full Chapter | LearnFatafat
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In this video, we will learn about Nutrition in Plants. Following topics are explained in this video -
What is nutrition?
The process of obtaining food is called nutrition. There are various ways by which plants obtain their food. They classified into autotrophic mode of nutrition and heterotrophic mode of nutrition.
A) Autotrophic mode of nutrition -
Green plants absorb carbon dioxide from air and water from soil. With the help of sunlight and chlorophyll they convert these materials into food. This process is called photosynthesis. Having ability of making own food are called autotrophs. Green plants, blue-green algae are some examples of autotrophs. The plants who make their own food are called as autotrophs. The kind of nutrition in which an organism prepare its own food is called autotrophic mode of nutrition.
B) Heterotrophic mode of nutrition -
The plants which can not produce their own food and so, these are dependent on green plants or other organisms for their food. Such mode of nutrition is called heterotrophic mode of nutrition.
The several ways of heterotrophic mode of nutrition are -
1) Parasitic Nutrition -
Some plants like cuscuta locally called amarbell grows over other plant and obtain nutrients from it. Such plant is called parasite and the plant over which it grows and obtain nutrients is called host. Such mode of nutrition in which organism obtain nutrient from other organisms body is called parasitic mode of nutrition.
2) Saprophytic Nutrition -
Some plants such as mushroom, yeast secrete digestive juices on dead part of the plant or animal so as to convert it into simple substances in solution form. They absorb nutrients from the solution so formed. Such mode of nutrition in which organism obtain nutrients from dead and decaying organic substances is called saprophytic mode of nutrition, and the organism which have this mode of nutrition are called saprotrophs.
3) Symbiotic Nutrition -
There are some organisms which live together like 'friends’; they share shelter and food. In science we call such relationship as symbiotic relationship. E.g. rhizobium bacteria and leguminous plants such as peas, moong, beans etc. The leguminous plant let the bacteria live in its roots and also provide food to it. On the other hand, the rhizobium bacteria convert nitrogen present in the soil in the form usable by the plant. In this way both are benefiting from each other.
4) Insectivorous Nutrition -
some plants like Venus flytrap, pitcher plant can eat insects. They are colorful to attract insects towards them. Part of their body such as leaves are modified into trap organs such as pitcher which helps for catching the insects. The hairs present in the pitcher hold the insect and does not let it escape. With the help of digestive enzymes they digest the food and obtain nutrients from it. There is need of conversion of complex matter in the form which can be used by plants. The job is done by bacteria such as rhizobium. The process of conversion of complex nitrogenous matter into simple forms such as ammonia that can be used by plants is called nitrogen fixation or nitrification.
Nitrogen cycle -
What is nitrogen cycle?
Nitrogen occurs as 78% part of atmosphere. The atmospheric nitrogen, is difficult to use hence, there is necessity to fix this nitrogen in its useful form.
The process of nitrogen cycle -
1) Fixation - It is first step of nitrogen cycle. In which free or elemental nitrogen is fixed by certain bacteria and converted into ammonium is called fixation.
2) Nitrification - Bacteria then converts ammonium into nitrates is called nitrification.
3) Assimilation - In which process, plants absorbs nitrogen from the soil through roots is called assimilation.
4) Ammonification - When plants and animals die, fungi and bacteria converts their nitrogen into ammonia and transfer it to nitrogen cycle.
5) Denitrification - There are special bacteria that converts extra nitrogen from the soil into it's elemental form and put them back into the air.
