Which substance enters through plant roots and is essential for photosynthesis?

• A. Glucose (\(C_6H_{12}O_6\))
• B. Oxygen (\(O_2\))
• C. Carbon dioxide (\(CO_2\))
• D. Water (\(H_2O\))

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the process of photosynthesis. Photosynthesis is the process by which plants convert light energy into chemical energy stored in glucose (\(C_6H_{12}O_6\)). This process requires water (\(H_2O\)), carbon dioxide (\(CO_2\)), and sunlight.
2. Step 2: Identify the role of water (\(H_2O\)) in photosynthesis. Water is absorbed through the roots of the plant and transported to the leaves via the xylem. It serves as a source of electrons and hydrogen ions during the light-dependent reactions of photosynthesis.
3. Step 3: Recall the light-dependent reactions. In these reactions, water molecules are split into oxygen (\(O_2\)), protons (\(H^+\)), and electrons through a process called photolysis, which occurs in the thylakoid membranes of chloroplasts.
4. Step 4: Eliminate the incorrect options. Glucose (\(C_6H_{12}O_6\)) is a product of photosynthesis, not a reactant. Oxygen (\(O_2\)) is released as a byproduct during the light-dependent reactions. Carbon dioxide (\(CO_2\)) is absorbed through the stomata in leaves, not through the roots.
5. Step 5: Conclude that water (\(H_2O\)) is the correct answer. It enters through the roots and is essential for photosynthesis, specifically in the light-dependent reactions where it is split to provide necessary components for the process.