Which of the following nutrients is essential for photosynthesis?

The correct answer is nitrogen, which plays a crucial role in the process of photosynthesis. Nitrogen is a key component of chlorophyll, the green pigment in plants that captures sunlight during photosynthesis. Without sufficient nitrogen, plants cannot produce enough chlorophyll, leading to lower photosynthesis rates and reduced growth.

Additionally, nitrogen is integral to the production of amino acids, proteins, and nucleic acids, all of which are vital for plant development and metabolism. By facilitating these essential functions, nitrogen helps to ensure that plants can effectively convert light energy into chemical energy, thus supporting their growth and survival. In contrast, while phosphorus, sulfur, and calcium are important nutrients for various plant functions, they do not have the same direct role in the process of photosynthesis as nitrogen does.