NUTRITION IN PLANTS [CLASS-7]

SCIENCE                  CLASS-7

       

NUTRITION IN PLANTS

1. NUTRIENTS

Carbohydrates, Proteins, Fats, Vitamins and Minerals are called nutrients.

2. FOODS

The digestible organic substances containing nutrients are called foods.

3.NEED OF FOOD

For a living organism, food provides energy for growth and maintenance the body.

4.NUTRITION

The mode of taking food by an organism and its utilisation by the body is called nutrition.

5.MODE OF NUTRITION IN PLANTS

A. AUTOTROPHIC NUTRITION :- By all green leafy plants
B. HETEROTROPHIC NUTRITION :- By Cascuta(Amarbel) and Pitcher Plants
C. SAPROTROPHIC NUTRITION :- By Mashroom ( Fungi)

6. AUTOTROPHIC NUTRITION

• The mode of nutrition in which organisms make food themselves from simple inorganic substances is called autotrophic nutrition [auto=self; trophos = nourishment ] and the organisms are called autotrophs.


• All green plants are autotrophs.


• Heterotrophs:- Animals and most other organisms take in food prepared by plants,are called heterotrophs.

7. PHOTOSYNTHESIS

• Food factories of plants - Leaves
• Photosynthesis :- This is the food making process in green plants.
• Necessary things used in photosynthesis :- (i)water (ii) carbon dioxide (iii)sunlight (iv)chlorophyll
• Chlorophyll:- It is the green pigment. It helps leaves to capture sunlight energy. It makes the leaves green.
• Representation of photosynthesis as an equation
  
  
  




• Main products of photosynthesis:- (i)Glucose (ii) Oxygen gas


• Site of photosynthesis - Leaves , Stems
• Cellular site of photosynthesis - Chloroplast
• Photosynthesis in various coloured plants:- In croton like plants, another colours found in large amount, mask the green colour.So, these plants also perform photosynthesis.

8.ROLE OF THE LEAF IN PHOTOSYNTHESIS

• STOMATA :- The tiny pores on the sueface of the leaves surrounded by two kidney - shaped guard cells are called stomata.Guard cells regulate the opening and closing of stomata. These kidney - shaped cells cover a single stoma and also contain chloroplasts.
• FUNCTIONS OF STOMATA :-(i) Exchange of gases takes place. Carbon dioxide from air is taken in and oxygen is released through stomata.
  (ii) Transpiration takes place through stomata.

9. OTHER MODES OF NUTRITION IN PLANTS

(a) Saprotrophic (b)Parasitic (c) Symbiotic relationship (d)Insectivorous or Carnivorous plants

(a)SAPROTROPHIC NUTRITION:-

The mode of nutrition in which organisms take in nutrients in solution form from dead & decaying matter is called saprotrophic nutrition. Plants which use such a mode of nutrition are called saprotrophs. These plants are usually whitish. They have no green leaves; often, they even have no leaves at all. Examples of fungi are: (i)Mushrooms are fluffy umbrella-like patches growing on rotting wood during the rainy season. (ii)Bread molds are cotton-like threads spread on the bread.

(b) Parasitic:-

Certain plants lack chlorophyll pigments (without which photosynthesis cannot take place) and are thus parasites on other plants. These plants obtain the food prepared by other organisms. Examples are Cuscuta (Dodder), Rafflesia, etc.

(c)Symbiotic Relationship

Mutually beneficial association in which two organisms live together and share shelter and nutrients. This is called a symbiotic relationship—for example, Mycorrhiza and lichen.

(d) Insectivorous or carnivorous plants

Insectivorous plants are autotrophic but obtain nitrogen from insects. They generally grow in soil that is deficient in nitrogen, such as Nepenthes or Pitcher plants. Venus flytrap, Sundew etc.

Question 1: Why do organisms need to take food?
Answer: All organisms need to take food to get energy for the growth, development, locomotion and maintenance of their bodies.

Question 2: Distinguish between a parasite and a saprotroph.
Answer: Difference between a parasite and a saprotroph

S.No.	Parasite	Saprotroph
1.	Organisms derive nutrition from the body of other living organisms (host) are parasites.	Plants which derive nutrition from dead and decaying organisms are called saprotrophs.
2.	Example: Cuscutta	Example: Mushrooms

Question 3: How would you test the presence of starch in leaves?
Answer: 1. Take a potted plant with variegated leaves – for example, money plant or crotons. 2. Keep the plant in a dark room for three days so that all the starch gets used up. 3. Now select a leaf cover its portion with a black strip paper and keep the plant in sunlight for about six hours.