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Which gas is responsible for causing stiffness (blast damage) in flower buds?

1. Sulphur dioxide
2. Carbon monoxide
3. Carbon dioxide
4. Nitrogen dioxide

Correct answer: Sulphur dioxide

Solution

Sulphur dioxide (SO2) is the air pollutant known to cause 'blossom blast' in plants. When SO2 enters floral tissue it forms H2SO3 (sulphurous acid), which damages cells, causing stiffening and browning of flower buds so they fail to open. CO, CO2, and NO2 do not specifically cause this condition.

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