Adjuvants are used to improve absorption by foliage under what condition?

• A. They are required on all crops
• B. They are used to enhance photosynthesis
• C. They decrease absorption by waxy leaves
• D. They improve absorption by waxy or hairy foliage

Answer: (D)

Adjuvants help sprays overcome leaf surface barriers to uptake, especially when leaves have surfaces that are hard to wet or penetrate. Waxy cuticles and hairy foliage create a hydrophobic barrier and trap droplets, so absorption can be poor. An adjuvant lowers surface tension and improves spreading and wetting, and some types can aid penetration through the cuticle. That’s why they’re used to improve absorption on waxy or hairy foliage.

The other statements don’t fit: adjuvants aren’t required on all crops, they aren’t used to boost photosynthesis, and they don’t decrease absorption—their purpose is to increase absorption where the leaf surface presents a barrier.