Which nutrient is known to be less mobile within the plant and commonly leads to deficiency?

Iron is known to be less mobile within the plant, meaning that once it is utilized in a particular tissue, it does not move easily to other parts of the plant. This immobility can often lead to iron deficiency, particularly in younger leaves, as the plant is unable to redistribute the limited iron resources from older tissues. Plants typically exhibit symptoms of deficiency, such as chlorosis (yellowing of leaves), in the upper foliage because the younger leaves do not receive adequate iron.

In contrast, the other nutrients listed, such as nitrogen, phosphorus, and potassium, are generally more mobile within the plant. These nutrients can be relocated from older tissues to support growing tissues, which means that their deficiencies often manifest differently and can affect a wider range of leaves. Therefore, iron's lower mobility is key in understanding its deficiency symptoms and management in plant science.