Two identical seedlings are grown in good light with plenty of water; one receives nitrate and the other receives none. The one without nitrate stays small. Why?

الشرح

Growth means building new cells, and new cells need protein, so a plant short of the mineral used to make protein has no way to add tissue even while energy is plentiful. Calling such a plant starving misreads the problem, because with light and water present it is making sugar perfectly well and what it lacks is a building material rather than a fuel.