×

Guest User

Share With Us:

Subjects /Class 7 / Science.7 / Nutrition in Plants

top event

INTRODUCTION
29 Jun 2022

We know that food is essential for all living organisms. Carbohydrates, proteins, fats, vitamins and minerals are components of food. These parts of food are vital for our body and are called supplements or nutrients.

The food gives energy to the living beings for development and support of their body capacities.

What is Nutrition

Nutrition is the method involved with taking food by an organism and its usage by the body.

Green plants prepare their own food while humans and animals are directly or indirectly dependent on plants for their food.

The food has nutrients which enable living organisms to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry out life processes.


The Modes of Nutrition in Plants

Nutrition is the mode of taking food by an organism and its utilization by the body.

There are two modes of nutrition:

  • Autotrophic
  • Heterotrophic

Autotrophs:

  • The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition (auto = self; trophos = nourishment).
  • Plants are the autotrophs.
  • They prepare their food by using raw materials like CO2, Water and minerals. They get these raw materials from their surroundings.
  • Plants that have chlorophyll trap the energy from the sun and prepare their own food. Food is prepared by the organisms itself is called autotrophic nutrition.

Heterotrophs:

  • The mode of nutrition in which organisms obtain food from other organisms is called hetrotrophic nutrition ( heteros = other; trophos = nourishment).
  • Animals and most other organisms take in food prepared by plants. They are called heterotrophs.
  • The organisms who depend on other organisms for their food they are also called consumers.

The Modes of Nutrition in Plants

Nutrition is the mode of taking food by an organism and its utilization by the body.

There are two modes of nutrition:

  • Autotrophic
  • Heterotrophic

Autotrophs:

  • The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition (auto = self; trophos = nourishment).
  • Plants are the autotrophs.
  • They prepare their food by using raw materials like CO2, Water and minerals. They get these raw materials from their surroundings.
  • Plants that have chlorophyll trap the energy from the sun and prepare their own food. Food is prepared by the organisms itself is called autotrophic nutrition.

Heterotrophs:

  • The mode of nutrition in which organisms obtain food from other organisms is called hetrotrophic nutrition ( heteros = other; trophos = nourishment).
  • Animals and most other organisms take in food prepared by plants. They are called heterotrophs.
  • The organisms who depend on other organisms for their food they are also called consumers.

Other Modes of Nutrition in Plants

There are some plants which do not have chlorophyll. They cannot synthesis food. Such plants depend on the food produced by other plants. They use the heterotrophic mode of nutrition. Different modes of nutrition in plants are:

  • Parasitic mode of nutrition
  • Insectivorous mode
  • Saprophytic mode of nutrition
  • Symbiotic mode of nutrition

Parasitic mode of nutrition:

In this mode of nutrition, plants depend on other animals, or plants for their nourishment. Such dependent plants are called as parasites and the ones on which parasites depend are called as hosts.

Let us take an example of a plant called Cuscuta:

  • It does not have chlorophyll.
  • It takes ready made food from the plant on which it is climbing.
  • The plant on which it climbs is called the host.
  • Since it deprives the host of valuable nutrients, Cuscuta is called the parasite.

Other examples are:

Roundworm, Cuscuta, Cuscuta (dodder), Mistletoe plant, Rafflesia

Insectivorous mode:

In this mode of nutrition, plants like Pitcher plant and the Venus fly trap trap insects and digest them.

These types of plants purely depend on other small animals and insects for their nutrition.

Let us take an example of Pitcher plant:

  • The pitcher-like or jug-like structure is the modified part of leaf.
  • The apex of the leaf forms a lid which can open and close the mouth of the pitcher.
  • Inside the pitcher there are hair which are directed downwards.
  • When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair.
  • The lid closes and the insect is trapped.
  • The insect is digested by the digestive juices secreted in the pitcher and its nutrients are absorbed.

Other examples are:

Pitcher plant, Venus flytrap, Sundew

Saprophytic mode of nutrition:

In this mode of nutrition, organisms take in nutrients from dead and decaying matter.

They don’t feed on a living organism. Such organisms with saprotrophic mode of nutrition are called saprotrophs.

Let us take an example of Fungi:

  • It grows on pickles, leather, clothes and other articles that are left in hot and humid weather for long time.
  • During rainy season they spoil many things.
  • The fungal spores are generally present in the air.
  • When they land on wet and warm things they germinate and grow.
  • You might have seen a bread turning green or black, it is because of the fungi.

Other examples are:

Fungi, Mushroom, Bacteria, Moulds, Yeasts

Symbiotic mode of nutrition:

In this mode of nutrition there is a close association between two different plants of different categories. In such type of association both the plants get benefited. They live together and share both shelter and nutrients. This relationship is called symbiosis.

For example:

  • Certain fungi live in the roots of the trees. The plants provide nutrients to the fungus and in return, the fungus provides water and certain nutrients.
  • In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and minerals to the alga and, in return, the alga prepares and provides food to the fungus.

How Nutrients are Replenished in the Soil

Plant absorb minerals and nutrients from the soil. So, their amounts in the soil keep on declining.

Fertilisers and manures contain nutrients such as nitrogen, potassium, phosphorous, etc.

These nutrients need to be added from time to time to enrich the soil. We can grow plants and keep them healthy if we can fulfil the nutrient requirement of plants.

Role of Nitrogen in Soil

  • Crop plants absorb a lot of nitrogen and the soil becomes deficient in nitrogen.
  • Though nitrogen gas is available in plenty in the air, plants cannot use it in the manner they can use carbon dioxide. They need nitrogen in a soluble form.
  • The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a usable form. But Rhizobium cannot make its own food.
  • So, it often lives in the roots of gram, peas, moong, beans, and other legumes and provides them with nitrogen.
  • In return, the plants provide food and shelter to the bacteria. They, thus, have a symbiotic relationship.
  • This association is of great significance for the farmers. They can reduce the use of nitrogenous fertilizer where leguminous plants are grown. Most of the pulses (dals) are obtained from leguminous plants.

NCERT SOLUTIONS

1. Why do organisms take food?

All living beings need to take food to get energy for the development, improvement, balance of their bodies, it gives immunity against diseases etc.

2. Distinguish between a parasite and a saprotroph.

Parasite

Saprotrophs

It feeds on a living organism

They feed only dead and decaying organisms

The organism on which it feeds is known as host.

They don’t feed on a living organism

Eg: Roundworm, Cuscuta

Eg: Fungi, Mushroom, Bacteria

3. How would you test the presence of starch in leaves?

The presence of starch in leaves can be tried or tested by Iodine test. At the point when we eliminate chlorophyll from leaf by bubbling it in liquor and afterward put 2 drops of iodine solution, its shading or colour change to blue indicates the presence of starch.

4. Give a brief description of the process of synthesis of food in green plants

The green plants have chlorophyll in the leaves.

The leaves use C02 and water to make food in presence of sunlight.


5. Show with the help of a sketch that plants are the ultimate source of food.


6. Fill in the blanks:

(a) Green plants are called _________________ since they synthesise their own food.

(b) The food synthesised by plants is stored as _________________.

(c) In photosynthesis solar energy is absorbed by the pigment called ___________.

(d) During photosynthesis plants take in ______________________ and release __________________ gas.

Solution:

(a) Green plants are called autotrophs since they synthesise their food.

(b) The food synthesised by plants is stored as starch.

(c) In photosynthesis, solar energy is absorbed by the pigment called chlorophyll.

(d) During photosynthesis, plants take in carbon dioxide and release oxygen gas.

7. Name the following:

i) A parasitic plant with yellow, slender and branched stem.

ii) A plant that is partially autotrophic.

iii) The pores through which leaves exchange gases.

Solution:

i) Cuscuta

ii) Pitcher plant, Venus Flytrap

iii) Stomata

8. Tick the correct answer:

(a) Cuscuta is an example of:

(i) autotroph

(ii) parasite

(iii) saprotroph

(iv) host

(b) The plant which traps and feeds on insects is:

(i) Cuscuta

(ii) china rose

(iii) pitcher plant

(iv) rose

Solution:

(a) (ii) Parasite

(b) (iii) pitcher plant

9. Match the items given in Column I with those in Column II:

Column- I

Column-II

Chlorophyll

Rhizobium

Nitrogen

Heterotrophs

Cuscuta

Pitcher plant

Animals

Leaf

Insects

Parasite

Solution:

Column- I

Column-II

Chlorophyll

Leaf

Nitrogen

Rhizobium

Cuscuta

Parasite

Animals

Heterotrophs

Insects

Pitcher plant

10. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) Carbon dioxide is released during photosynthesis. (T/F) - FALSE

(ii) Plants which synthesise their food are called saprotrophs. (T/F) - FALSE

(iii) The product of photosynthesis is not a protein. (T/F) - TRUE

(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F) - TRUE

11. Choose the correct option from the following:

Which part of the plant takes in carbon dioxide from the air for photosynthesis?

(i) Root hair (ii) Stomata (iii) Leaf veins (iv) Petals

Solution:

(ii) Stomata

12. Choose the correct option from the following:

Plants take carbon dioxide from the atmosphere mainly through their:

(i) roots (ii) stem (iii) flowers (iv) leaves

Solution:

(iv) Leaves

13. Why do farmers grow many fruits and vegetable crops inside large greenhouses? What are the advantages to the farmers?

Vegetable crops and fruits both are filled in huge nurseries or green houses since it shields or protects crops from outer climatic condition and to give appropriate temperature to the development of yields.

Benefits of Farmers:

It protects crops from unfavourable climatic conditions and diseases

It protects crops from rodents and winds.