Which of the following is NOT a nutrient required by plants?

Hydrogen is often considered to be a component in various biochemical processes, but it is not classified as a nutrient in the same way that nitrogen, sulfur, and potassium are. While hydrogen is essential for the formation of water and organic molecules, it is typically acquired by plants through the splitting of water molecules during photosynthesis, rather than being absorbed from the soil like traditional nutrients.

Nitrogen is crucial for the synthesis of amino acids and nucleic acids, making it vital for plant growth and development. Sulfur plays an essential role in the formation of proteins and enzymes, while potassium is important for many physiological functions, including enzyme activation and water regulation. Each of these three elements can be absorbed directly from the soil, highlighting their classification as essential nutrients for plants.

In contrast, while hydrogen is indispensable to life and plant processes, it does not fit within the conventional nutrient framework because it is not obtained through soil uptake in the same manner as the others.