Answer: They would be able to obtain more carbon dioxide than normal
Explanation:
Plants “breath” carbon dioxide and produce oxygen in the process of photosynthesis, if plants get less carbon dioxide than normal they will not be able to carry this process on as sufficiently as if it were to have no outer coating. The wax will block out the CO2 and the plant will most likely be weaker than most plants. (This is for if the plant is still “together”, not if you’re talking about say an apple that is coated with a waxy substance).