- Books Name
- CBSE Class 7 Science Book
- Param Publication
- CBSE Class 7
The process by which green plant prepare their food in the presence of sunlight, (Carbondioxide)CO2 , water, chlorophyll.
There are four requirement for photosynthesis.
(A) Sunlight:- It comes from sun & provide energy for photosynthesis.
(B) Carbon dioxide (CO2):- It is obtained from air and taken through tiny pores called stomata present on the under surface of leaves.
(C) Chlorophyll:- The chlorophyll is present in the chloroplast. Chloroplast regarded as Kitchen of cell and present in Green leaves.
• Besides chlorophyll cetain other pigments are also present in plants like :
(a) Carotenes : Organe in colour e.g. Carrot.
(b) Xanthophylls : Orange yellow in colour e.g. Maize.
(c) Phycobilins : Different colours like red, violet e.g., Blue-green algae, brown algae etc.
(D) Water (H2O):- They are obtained from the soil by the roots of plants and are transported to the leaves.
Plants have Vascular tissues called Xylem & Phloem.
(i) Xylem transport water and minerals to the leaves.
(ii) Phloem transport food (Sucrose) to various part of plant.
Photosynthesis – food making process in plants
The plants use the energy in sunlight to prepare food in the presence of a green colour matter called “chlorophyll” present in the leaves of a green plant. The process by which green plants make their own food (like glucose) from carbon dioxide and water by using sunlight energy (in the presence of chlorophyll) is called photosynthesis.
Carbon dioxide + Water → Glucose + Oxygen The process of photosynthesis takes place in the leaves of a plant. Oxygen gas is produced during photosynthesis which is utilised by all the living organisms for their survival. The process of photosynthesis first produces a simple carbohydrate called ‘glucose’ as food. The glucose carbohydrate then gets converted into a complex carbohydrate called Starch. Starch gets stored as food in the various parts of plant including leaves. Some of the glucose is also converted into other types of plant foods such as fats and oils, proteins as well as vitamins. The synthesis of food (or making of food) occurs in the leaves of a plant, so leaves are the food factories of a plant. The leaves of a plant can synthesise food because they contain a green pigments chlorophyll (which is necessary for making food). Other parts of a plant usually cannot synthesise food because they do not contain chlorophyll.