Answers to Analyzing Data 5.1 Questions

Note: Numerical answers may vary slightly due to differences in interpolation from the graph.

1.

a. High-light grown plant Gains: (2.5 μmol∕m²∕s ? 7200 s) + (32 μmol∕m²∕s ? 36,000 s) + (2.5 μmol∕m²∕s ? 7200 seconds) = 1,188,000 μmols CO₂∕m² or 1.188 mols CO₂∕m²

Losses: 3 μmol∕m²∕s ? 36,000 s = 108,000 μmols CO₂∕m² or 0.108 mols CO₂∕m²

Total daily balance for the high-light grown plant: +1.08 mols CO2∕m²

Low-light grown plant

Gains: (2.5 μmol∕m²∕s ? 7200 s) + (5 μmol∕m²∕s ? 36,000 s) + (2.5 μmol∕m²∕s ? 7200 seconds) = 216,000 μmols CO₂∕m² or 0.216 mols CO₂∕m²

Losses: 2 μmol∕m²∕s ? 36,000 s = 72,000 μmols CO₂∕m² or 0.072 mols CO₂∕m²

Total daily balance for the high-light grown plant: +0.144 mols CO2∕m²

b.

Gains: (-2 μmol∕m²∕s ? 7200 s) + (2.5 μmol∕m²∕s ? 36,000 s) + (-2 μmol∕m²∕s ? 7200 seconds) = 61,200 μmols CO₂∕m² or 0.0612 mols CO₂∕m²

Losses: 3 μmol∕m²∕s ? 36,000 s = 108,000 μmols CO₂∕m² or 0.108 mols CO₂∕m²

Total daily balance for the high-light grown plant: -0.047 mols CO₂∕m²

Low-light grown plant

Gains: (0 μmol∕m²∕s ? 7200 s) + (2.5 μmol∕m²∕s ? 36,000 s) + (0 μmol∕m²∕s ? 7200 seconds) = 90,000 μmols CO₂∕m² or 0.090 mols CO₂∕m²

Losses: 2 μmol∕m²∕s ? 36,000 s = 72,000 μmols CO₂∕m² or 0.072 mols CO₂∕m²

Total daily balance for the high-light grown plant: +0.018 mols CO₂∕m²

2. The higher light saturation point in the high-light grown plants contributed significantly to the more positive carbon balance relative to the low-light grown plants when exposed to high-light conditions.

3. Low-light grown plants have lower concentrations of enzymes to support photosynthesis, and thus will have lower respiratory rates and lower carbon loss at night.