YOU SAID:

the air outside the leaf is a lot drier than the air inside the leaf

INTO JAPANESE

葉の外側の空気は、葉の内側の空気よりもかなり乾燥しています

BACK INTO ENGLISH

The air outside the leaves is considerably dryer than the air inside the leaves

INTO JAPANESE

葉の外側の空気は、葉の内部の空気よりもかなり乾燥している

BACK INTO ENGLISH

The air outside the leaves is considerably dryer than the air inside the leaves