Food factories

The idea

Starch is produced only where chlorophyll is present and only in sunlight; chlorophyll is essential for preparing starch, so leaves are called the 'food factories' of plants.

Bhaskar's two plants

Bhaskar takes a leaf with green and non-green patches from each of two similar plants. One plant was kept in sunlight. The other was kept in the dark for 36 hours.

Which leaf will turn blue-black on its green patches?

• The leaf from the plant kept in sunlight
• The leaf from the plant kept in the dark
• Both leaves

Test both leaves

Add iodine to each leaf. The leaves were decolourised first. The dashed line shows where the green patch was.

Chlorophyll and sunlight

Only the green patches of the leaf from the sunlight turned blue-black. The leaf from the dark had no starch at all. So chlorophyll helps prepare starch in sunlight.

Starch is produced only where chlorophyll is present and only in sunlight; chlorophyll is essential for preparing starch, so leaves are called the 'food factories' of plants.

• Leaf | Green patches | Non-green patches
• From the plant in sunlight | Blue-black | Not blue-black
• From the plant in the dark | Not blue-black | Not blue-black

Notes

Starch is produced only where chlorophyll is present and only in sunlight; chlorophyll is essential for preparing starch, so leaves are called the 'food factories' of plants.

Check yourself

The leaf from the plant in sunlight turned blue-black on …

The leaf from the plant kept in the dark did not turn blue-black, even on its green patches. What does this show?

Along with sunlight, what is essential for preparing starch?

Why are leaves called the 'food factories' of plants?

• its green patches only — correct. Yes! Starch was made where chlorophyll is present.
• its non-green patches only. Starch was found on the green patches, where chlorophyll is.
• the whole leaf equally. The non-green patches did not turn blue-black.
• A leaf in the dark has more starch. If it had starch, it would turn blue-black. It did not.
• Starch is not produced without sunlight — correct. Yes! Sunlight is needed.
• Chlorophyll alone is enough to make starch. The green patches had chlorophyll, but no starch was made in the dark.
• Iodine solution. Iodine is only used to test for starch. It does not help prepare it.
• Darkness. Starch is produced only in sunlight, not in darkness.
• Chlorophyll — correct. Yes! Chlorophyll is essential.
• They prepare starch, using chlorophyll and sunlight — correct. Yes! They make the plant's food.
• They eat food like animals do. Plants do not eat food like animals. Leaves prepare it.
• Their broad flat shape is only for decoration. The broad, flat shape helps to catch sunlight.