Overall Output of Photosynthesis—Select the Correct Product As a result of oxygenic photosynthesis in plants, which of the following is produced as a net product of the process?

Introduction / Context:
In the overall photosynthetic reaction, plants use carbon dioxide and water to form carbohydrates and release oxygen gas. Understanding which molecules are consumed and which are produced helps clarify the role of photosynthesis in global biogeochemical cycles and ecosystem respiration balance.

Given Data / Assumptions:

• Oxygenic photosynthesis splits water at photosystem II.
• CO2 is fixed during the Calvin cycle into carbohydrates.
• We are considering net products, not transient intermediates.

Concept / Approach:
The classic summary is: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 (simplified stoichiometry). Water is consumed, not produced, in the light reactions; additional water may appear in various metabolic reactions, but the canonical net effect is oxygen generation and carbohydrate synthesis. Carbon dioxide is a reactant, not a product. Therefore, the best answer among the options is oxygen alone.

Step-by-Step Solution:

Verification / Alternative check:
Isotopic labeling with 18O-labeled water leads to 18O in the O2 evolved, confirming water as the oxygen source and O2 as a product.

Why Other Options Are Wrong:

• Water: primarily a reactant consumed during light reactions.
• Carbon dioxide: a substrate for fixation, not a product.
• Both oxygen and water: incorrect because net water production is not the hallmark output.
• Nitrogen gas: unrelated to photosynthetic outputs.

Common Pitfalls:
Confusing cellular respiration (which consumes O2 and produces CO2) with photosynthesis.

Final Answer:
Oxygen