Can plants directly use sulfuric acid? In the explanation of the sulfur cycle, it is often said that sulfur moves from the atmosphere to the ground by acid rain in the form of sulfuric acid. Can plants directly use sulfuric acid to assimilate sulfur?

Plants have sulfate transporters which they use to assimilate sulfur. Since sulfate is the conjugate base of sulfuric acid, this **could** be construed as a "yes" for your question. Sulfuric acid would be present in its conjugate base form at physiological pH values.

However, it would be unwise to water your plants with sulfuric acid, as many plants have an optimal pH range which will quickly cause death when sulfuric acid lowers the pH of the soil below that range. As a result, areas afflicted by acid rain may require treatment with alkaline limestone to resolve this issue.