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Plant Life - The Leaf and Photosynthesis

Grade 4ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

The leaf is known as the 'Kitchen' or 'Food Factory' of the plant because it prepares food through the process of photosynthesis.

A leaf consists of several parts: the leaf blade (Lamina), the stalk (Petiole), the main vein (Midrib), and side veins which transport H2OH_2O and minerals.

Stomata are tiny pores found mostly on the underside of the leaf that help in the exchange of gases like Carbon Dioxide (CO2CO_2) and Oxygen (O2O_2).

Photosynthesis is the process by which green plants make food using CO2CO_2, H2OH_2O, and Sunlight in the presence of Chlorophyll.

Chlorophyll is a green pigment that captures solar energy. Without it, the plant cannot produce C6H12O6C_6H_{12}O_6 (Glucose).

Transpiration is the process where plants release excess water in the form of water vapor through the stomata.

The food prepared by the plant is a simple sugar called glucose, but it is stored in the form of a complex carbohydrate called Starch.

📐Formulae

Carbon Dioxide+WaterChlorophyllSunlightGlucose+Oxygen\text{Carbon Dioxide} + \text{Water} \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} \text{Glucose} + \text{Oxygen}

6CO2+6H2OSunlightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{Sunlight}} C_6H_{12}O_6 + 6O_2

💡Examples

Problem 1:

Identify the gas released by plants during photosynthesis that is essential for the survival of animals.

Solution:

Oxygen (O2O_2)

Explanation:

During photosynthesis, plants take in CO2CO_2 and release O2O_2 as a byproduct, which animals and humans need for breathing.

Problem 2:

What will happen to a leaf if it is kept in a dark room for 48 hours and then tested with Iodine solution?

Solution:

The leaf will not turn blue-black; it will show a brownish color.

Explanation:

In the dark, the leaf cannot perform photosynthesis due to lack of sunlight. Therefore, no starch is produced. Since Iodine only turns blue-black in the presence of starch, the test will be negative.

Problem 3:

Why are leaves generally green in color?

Solution:

Due to the presence of Chlorophyll.

Explanation:

Chlorophyll is a green-colored pigment that helps the plant absorb energy from sunlight to synthesize food.

The Leaf and Photosynthesis - Revision Notes & Key Formulas | ICSE Class 4 Science