A plant is given plenty of light, water and carbon dioxide but no nitrate ions at all. Which substances will it then be unable to make in normal amounts?

Explanation

Nitrate supplies a plant with the element it cannot obtain from air or water and that it needs in order to turn sugar into the building blocks of protein, so a plant deprived of it stalls at that step. Sugar production itself is untouched here, because the question states that every raw material for making sugar is present, and a store of starch is only surplus sugar packed away, so it needs no nitrate either.