Which element is essential for the formation of glucose during photosynthesis?

The correct answer is carbon, as it plays a crucial role in the formation of glucose during photosynthesis. In this process, carbon dioxide from the atmosphere enters the plant through small openings called stomata. Inside the plant cells, specifically in the chloroplasts, carbon dioxide is fixed through a series of reactions known as the Calvin cycle.

During these reactions, carbon atoms from carbon dioxide combine with other molecules to eventually form glucose, a six-carbon sugar used by the plant as an energy source and as a building block for other organic compounds. This process not only provides energy for the plant but also contributes to the overall carbon cycle in the ecosystem.

The other elements mentioned—hydrogen, oxygen, and nitrogen—while also important for various biological processes, do not have the same fundamental role as carbon in the synthesis of glucose. Hydrogen is involved in forming water and is part of glucose, oxygen is released as a byproduct during photosynthesis and is also part of glucose, and nitrogen is essential for the production of amino acids and proteins but is not directly used in glucose formation.