Question

How do we know that the leaf has prepared the starch and not received it from any other part of the plant

Answer 1

if we test the leaf with iodine if leaf turns bluish black starch is present if it doesn't change it means starch is not present

hope it helps you

Answer 2

Leaf  has prepared the starch and not recieve it

Explanation:

• Plants produce/manufacture (hence, factories) their own food from carbon dioxide and water in the presence of sunlight and chlorophyll, a green pigment which absorbs light energy; is concentrated in the chloroplasts found in green stems, sepals and leaves to yield sugar (food) and oxygen. So it's the abundance of chlorophyll in leaves is what makes them the photosynthetic or food factories.
• Roots, especially those with attached tubers, or other underground parts like rhizomes or bulbs (rhizomes and bulbs are technically a modified stem, even though most gardeners perceive them as a root) are one of the most common places plants store food. Although storage structures are usually underground (because it protects the plant from animals that might eat that nutrient-rich structure, think like a carrot or potato) there are some plants that have modified storage structures above ground.
• In plants food is synthesized in leaves in specialized organelles known as chloroplasts.
• A typical plant cell contains about 10 to 100 chloroplasts and within the choloroplast the site of food synthesis is thylakoids (grana). During photosynthesis, chlorophyll containing cells of leaves in the presence of sunlight, use carbon dioxide and water to synthesise basic sugar called glucose.
• Use of iodine test for know the starch in leaf is present or not.
• A leaf is taken, that has been exposed to sunlight.
• The leaf is boiled in boiling water: To make the tissue more permeable to iodine.
• Extracting the chlorophyll out of the leaf: For clarity of the iodine test.
• The boiled leaf is taken in a test tube and immersed in alcohol.
• The test tube is then subjected to water bath.
• This process is continued until the alcohol turns green.
• The leaf is taken out and kept in a Petri dish.
• The leaf is iodine flooded.
• If the colour of the leaf turns brown, this signifies the presence of starch in the leaf.