Category : 7th Class
We have come to know about the nutrition in plants and animals in the previous classes. In this chapter, we will learn in detail about the nutrition, both in plants and animals. All kind of plants need food to survive, and the process by which plants obtain food and utilize them for their nutritional needs, is called nutrition in plants.
Plants obtain raw materials for making food from sun light and soil. The process, by which roots of a plant absorb necessary minerals (dissolved in water) from soil and sent them to whole part of the plant, is called transportation. The leaves of the plants are made up of thousands of tiny holes, called stomata, and chlorophyll. Sunlight and carbon dioxide enters into the leaves through stomata.
Look at the Following Picture of Stomata
Open and closed stomata are shown in the picture above. Carbon dioxide and water enters and oxygen is released, when stomata is open.
Photosynthesis is a process by which all the green plants prepare their own food . In this process, complex organic material is synthesized using carbon dioxide, water, and inorganic salts, in the presence of sunlight. Oxygen is produced during photosynthesis as by-product.
Let's know about the different types of nutrition, by which plants obtain their food.
The mode of nutrition, in which living organisms (green plants and algae obtain their food by the process of photosynthesis is known as autotrophic nutrition. In this process, plants get energy form Sun and minerals from soil, thereby make glucose or sugar to fulfill the nutritional need, necessary for their survival.
This food is then supplied to all the parts of plant. The extra food is stored as starch by the plant.
Look at the following picture of nutrition in plants:
Transportation and Transpiration in Plants
Roots of plants absorb minerals from soil and transport to whole part of the plants. Water acts as reactant and solvent in the cell metabolism. Minerals from soil travel throughout the plants through vascular tissues. Vascular tissue is consisting of xylem and phloem. Xylem of vascular tissues are responsible for transporting water and mineral ions from root to whole part of the plants. Phloem is responsible for transporting food to all the parts of plant. In other word phloem is involved in transporting substances of organic food prepared by the leaves during photosynthesis.
Look at the following picture of food transporting tissue
Fig (1) Vascular tissue Fig (2) Xylem and phloem
Vascular cylinder is the central part of the vascular tissue. Water is transported through the vascular cylinder. Cortex is lying between epidermis and vascular cylinder. Epidermis is the outer part of the vascular tissue. Transpiration is the process in which plants release extra water into atmosphere, through the small opening of stomata. It is the transpiration that makes possible the transportation of water and minerals, from the root to the leaves.
The plants that use the parasitic mode of nutrition are called parasitic plants. In the parasitic mode of nutrition, host plant gives nutrition to parasitic plants. The parasitic plants do not have chlorophyll and therefore they cannot make food for themselves. The roots of parasitic plants are modified for absorbing essential nutrients from the host plants.
Look at the following picture of a parasitic Plant
In the above picture the parasitic plant is climbing on the host plant.
The saprophytic plants are those, who obtain their food from the dead and decayed organic matter. They do not have chlorophyll in their leaves, therefore, they cannot perform the process of photosynthesis.
Look at the following picture of saprophytic plant
Apart from the above, there are some plants who fulfill their nutritional needs in an interesting way. They are as follows:
The plants, which obtain some or most of their nutrients by trapping and digesting insects, are known as insectivorous plants. The leaves of insectivorous plants are modified for trapping insects. These plants are also called carnivorous plants as they feed on other organisms. They grow where availability of nitrogen is less; and they fulfill their nitrogen requirement from insects. The pitcher of insectivorous plants catch the insects, and hair inside the pitcher kills .them. The wall of the pitcher secretes liquid for breaking the insects into small pieces and then they absorb them. For example. Pitcher plant.
Look at the following picture of Insectivorous plant
Pitcher plant Fly trap plant
Two or more plants, which are grown at the same place and help each other for survival are called symbiotic plants. Some part of food is obtained from one plant and some part is from the other. A relationship of mutual benefit or dependence is called symbiotic relationship. For example. Lichen.
Look at the following picture of Symbiotic plant
In the above picture two plants are helping each other for obtaining their food.
Which one of the following parts is responsible for absorbing water and minerals from soil?
(e) None of these
Which one of the following is called stomata?
(a) A dry leaf
(b) Photosynthesis process
(c) Root of the plants
(d) Tiny holes on the lower leaves
(e) None of these
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