IV. Answer the following questions in long:
1. What do you understand by nutrition? Explain any two modes of nutrition in plants.
2. Why do plants use nitrogen present in the soil? How is this nitrogen replenished in the soil
3. Explain how green plants prepare their own food.
4. How can you show that sunlight is necessary for photosynthesis?
Answers
Answer:
ANSWER 1
Modes Of Nutrition
The process of obtaining food and utilizing it to grow, stay healthy and repair any damaged body part is known as nutrition. Plants produce their food by taking raw materials from their surroundings, such as minerals, carbon dioxide, water and sunlight. There are two modes of nutrition:
- Autotrophic – Plants exhibit autotrophic nutrition and are called primary producers. Plants synthesis their food by using light, carbon dioxide and water.
- Heterotrophic – Both animals and human beings are called heterotrophs, as they depend on plants for their food
ANSWER 2
the nitrogen content gets replenished naturally in the soil due to the presence of a particular bacteria in the soil.these bacteria live in the soil.this is a symbiotic relationship. the bacteria lives in the roots of the plant.they obtain nutrition. they, in turn provide nitrogen to the plant
ANSWER 3
The process by which plants make food is named as photosynthesis. Photosynthesis is the process in which green plants use sunlight to make their own food. Photosynthesis requires sunlight, chlorophyll, water, and carbon dioxide gas. Chlorophyll is a substance in all green plants, especially in the leaves. Plants take in water from the soil and carbon dioxide from the air. Plants can perform photosynthesis only through leaves and not by other parts of the plant. Leaves have a special green pigment called chlorophyll which helps in the absorption of energy from the sun. The chloroplast present in the cells play a vital role in this process. The various steps involved in the process of photosynthesis are given below:
Absorption of light energy through the sun by chlorophyll present in leaves.
Conversion of light energy chemical energy. In this process, the water molecule splits into its respective components hydrogen and oxygen.
Carbon dioxide is reduced into carbohydrates like glucose by light energy utilizing the hydrogen and oxygen produced in the above step.
The reaction involved in photosynthesis is:
6CO²+6H²0→C⁶H¹²O⁶+6O²
Glucose is the simple food which is prepared first in the process of photosynthesis. Glucose and oxygen are the final products of photosynthesis. Starch is the food that gets stored in plant leaves. Starch is a polymeric carbohydrate consisting of a large number of glucose units linked by glycosidic bonds. It acts as stored energy in plants.
ANSWER 4
Photosynthesis is a biochemical process by which green plants synthesize simple sugars. The most important factor for photosynthesis is light. The rate of photosynthesis depends on the quantity and quality of light.
Procedure to prove light is essential for photosynthesis:
1) Take the potted plant and keep it in a dark place for 2-3 days so that the leaves get destarched.
2) Attach light proof black paper strips on both sides of the leaf with the help of paper clips.
3) Place the plant in sunlight for 3-4 hours.
4) Pluck the selected covered leaf and remove the black paper covering it.
5) Perform starch test by boiling leaf first in boiling water followed by boiling in alcohol over a water bath and then rinsing with cold water and again placing it in iodine solution.
Observation: The leaf turns blue-black except in the covered region. As the covered region did not receive light, photosynthesis did not occur. Hence no starch was formed there. The uncovered region received light and starch was formed there due to photosynthesis.
Result: Light is essential for photosynthesis