Higher CAM Photosynthesis: The Ultimate Water-Saving Strategy
Part of Transpiration — GCSE Biology
This higher tier covers Higher CAM Photosynthesis: The Ultimate Water-Saving Strategy within Transpiration for GCSE Biology. Transpiration process, stomatal control, factors affecting rate, plant adaptations, measuring transpiration, and practical investigations It is section 11 of 20 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Topic position
Section 11 of 20
Practice
20 questions
Recall
25 flashcards
Higher CAM Photosynthesis: The Ultimate Water-Saving Strategy
This section goes beyond the core GCSE specification but may appear in Higher tier synoptic questions.
The Problem
Desert plants face a dilemma: they need CO₂ for photosynthesis (requiring open stomata) but must minimize water loss in extreme heat.
The CAM Solution
Crassulacean Acid Metabolism (CAM) separates CO₂ uptake from photosynthesis:
Night (stomata open):
- Cool temperatures reduce transpiration
- CO₂ enters through open stomata
- CO₂ converted to malic acid and stored
Day (stomata closed):
- Stomata close to prevent water loss
- Malic acid releases CO₂ internally
- Photosynthesis proceeds using stored CO₂
Efficiency:
- CAM plants lose 50-100g water per 1g glucose made
- Normal plants lose 500-1000g water per 1g glucose
- 90% reduction in water loss