Question

$S{O}_2$ is a dangerous air pollutant and harms plant life. What changes in the plant indicates its toxic effects?

• A. Darkening of leaves
• B. Withering of leaves
• C. Falling of leaves
• D. Bleaching of leaves

Answer 1

The correct option is D Bleaching of leaves

Sulfur dioxide enters the leaves mainly through the stomata (microscopic openings) and the resultant injury is classified as either acute or chronic. Acute injury is caused by absorption of high concentrations of sulfur dioxide in a relatively short time. The symptoms appear as 2-sided (bifacial) lesions that usually occur between the veins and occasionally along the margins of the leaves. The colour of the necrotic area can vary from a light tan or near white to an orange-red or brown depending on the time of year, the plant species affected and weather conditions.