What is the primary nutrient deficiency symptom found in the leaves of a nitrogen-deficient corn plant?

In nitrogen-deficient corn plants, one of the most prominent visual symptoms is the yellowing of lower leaves. This phenomenon occurs because nitrogen is a crucial nutrient for plant growth and development, and it is often mobilized from older leaves to support the growth of new leaves and reproductive structures. As a result, when nitrogen is limited, the lower leaves—the older leaves—show signs of deficiency first.

The yellowing, also known as chlorosis, in the lower leaves indicates that the plant is unable to maintain adequate chlorophyll production, essential for photosynthesis. This yellowing typically progresses toward the tip of the leaf, leading to more pronounced symptoms if the deficiency persists. It is important for crop advisors to be able to identify this symptom, as it provides critical insight into the plant's nutrient needs, highlighting the importance of nitrogen in healthy corn production.