Which nutrient is used for energy delivery and DNA structure in plants?

Phosphorus plays a crucial role in energy delivery and DNA structure in plants, making it the correct choice. In plants, phosphorus is an essential component of adenosine triphosphate (ATP), which is the molecule that stores and transports energy within cells. When plants need energy for growth, metabolism, or other physiological processes, ATP is utilized, highlighting phosphorus's fundamental role in energy transfer.

Additionally, phosphorus is a key component of nucleic acids, which include DNA. The structural framework of DNA contains phosphate groups that are vital for the formation of the DNA backbone, thereby supporting genetic information storage and transmission. This dual function of phosphorus in energy metabolism and the structural integrity of DNA underscores its significance in plant biology.

Other options, while important nutrients for plant health, do not serve both functions of energy delivery and DNA structure in the same way. Nitrogen is indispensable for amino acids and proteins, potassium is important for water regulation and enzyme activation, and magnesium is a critical component of chlorophyll in photosynthesis. Each of these nutrients has distinct roles, but phosphorus uniquely stands out for its involvement in energy and genetic functions.