Real-World Applications of Photosynthesis Knowledge

1. C4 Crop Engineering (C4 Rice Project)

• Problem: Rice is a C3 plant — photorespiration wastes 25–40% of fixed carbon
• Goal: Engineer C4 photosynthesis into rice by introducing C4 genes (PEP carboxylase, PPDK, Kranz-like anatomy)
• Expected outcome: ~50% increase in rice yield, lower water requirement
• Status: IRRI (International Rice Research Institute) ongoing research

2. Greenhouse $CO_{2}$ Enrichment

• Supplementing $CO_{2}$ to 0.1% (from atmospheric 0.042%) increases C3 crop yields by 20–40%
• Based on Blackman's law: $CO_{2}$ is often the limiting factor in greenhouses with adequate light and temperature
• Not effective in C4 crops (their $CO_{2}$ concentrating mechanism already saturates $CO_{2}$ supply)

3. Photorespiration Inhibitors as Herbicides

• DCMU (dichlorophenyl-dimethylurea) blocks PS II electron transport — used as a herbicide
• Glycolate oxidase inhibitors could reduce photorespiration in C3 crops

4. Understanding Crop Distribution

• C3 crops (wheat, rice, potato): Best in temperate zones (20–25°C optimum)
• C4 crops (maize, sugarcane, sorghum): Best in tropical zones (30–40°C optimum)
• Climate change implications: Rising temperatures may shift C4 competitive advantage poleward

5. Water Use Efficiency (WUE)

• C4: Higher WUE (more $CO_{2}$ fixed per water lost) — important for drought-prone agriculture
• CAM: Highest WUE — but slow growth rate limits large-scale crop use

NEET Exam Context

Blackman's law, C4 advantages, and photorespiration are directly connected to agricultural productivity questions in NEET's application-based section.