What is a common symptom of nitrogen deficiency in plants?

Yellowing of leaves is a common symptom of nitrogen deficiency in plants, a condition often referred to as chlorosis. Nitrogen is a vital nutrient required for the synthesis of chlorophyll, the green pigment responsible for photosynthesis. When plants lack adequate nitrogen, the production of chlorophyll diminishes, leading to a yellowing of the younger leaves first, as they are typically more actively growing and rely heavily on nitrogen.

In this context, wilting leaves often suggest issues related to water, brown spots may indicate localized damage or diseases unrelated to nitrogen, and stunted growth could result from several deficiencies or adverse environmental conditions. The yellowing of leaves, however, specifically indicates a lack of nitrogen, making it the correct response to the question regarding nitrogen deficiency symptoms.