Oxygen released during photosynthesis is described as a waste product of plants. Justify this statement, and explain how plants manage to dispose of this 'waste' without a dedicated excretory organ.
Generated by claude-sonnet-4-6 · 2026-06-26 01:02 · grounding rag
Model Answer
During photosynthesis, water molecules are split to release hydrogen; oxygen is a by-product of this reaction and is not used further by the plant, making it a waste product.
Plants dispose of it through simple diffusion — oxygen passes out directly through stomata and the surfaces of leaves, stems, and roots into the surrounding air. No specialised excretory organ is needed because gases diffuse easily across thin cell surfaces.
Source: Life Processes, Section 5.5.2 Excretion in Plants; Section 5.2.1 Autotrophic Nutrition
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Explanation
- The examiner wants two things: (1) why O₂ is a waste (it's a by-product of water-splitting in photosynthesis, not used by the plant), and (2) how it is removed (diffusion through stomata/cell surfaces — no organ needed).
- Don't confuse O₂ released in photosynthesis with O₂ consumed in respiration; some O₂ is reused internally, but the excess is excreted as waste.
- The key term is diffusion — plants rely on it because gaseous molecules move easily across moist cell surfaces, unlike bulky nitrogenous wastes that need specialised organs.