Describe and carry out investigations using whole plants, including aquatic plants, to determine the effects of light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis

Sourav PanOctober 31, 2024

Answered

Investigation: Effects of Environmental Factors on Photosynthesis in Whole Plants

Objective:
To investigate the effects of Light Intensity, Carbon Dioxide (CO2) Concentration, and Temperature on the Rate of Photosynthesis in various whole plants, including aquatic plants.

Materials:

• Whole Plants:
  • Terrestrial plants (e.g., radish, alfalfa, or bean sprouts)
  • Aquatic plants (e.g., water hyacinth, duckweed, or cabomba)
• Light Sources:
  • Variable light intensity (using lamps or shades)
  • Natural light (outdoor experiments)
• CO2 Concentration:
  • CO2 gas cylinders or bags with different concentrations
  • NaOH (sodium hydroxide) for increased CO2 absorption
• Temperature Control:
  • Thermometers
  • Heating/cooling systems (e.g., water baths, thermoses)
• Measuring Photosynthesis:
  • Infrared gas analyzers (IRGA) or CO2 sensors
  • Oxygen electrodes or meters

Procedure:

1. Select Whole Plants:
   • Choose plants with varying growth rates and responses to environmental factors.
2. Prepare Experimental Setup:
   • Terrestrial plants: potting soil with controlled nutrient levels.
   • Aquatic plants: aquarium water with measured parameters (e.g., pH, nutrient levels).
3. Variable Environmental Conditions:
   • Light Intensity:
     • Low (e.g., 10 μmol/m²s)
     • Medium (e.g., 50 μmol/m² s)
     • High (e.g., 100 μmol/m² s)
   • CO2 Concentration:
     • Low (e.g., 200 ppm)
     • Medium (e.g., 400 ppm)
     • High (e.g., 800 ppm)
   • Temperature:
     • Low (e.g., 15°C)
     • Optimal (e.g., 25°C)
     • High (e.g., 35°C)
4. Measure Photosynthesis:
   • Use IRGA or CO2 sensors to measure net CO2 uptake or oxygen evolution.
   • Record plant growth (e.g., biomass, leaf area, or stem length) over time.
5. Data Analysis:
   • Calculate the rate of photosynthesis (e.g., μmol CO2/m² s)
   • Compare growth rates among treatments

Example Experimental Design:

| Treatment | Light Intensity (μmol/m² s) | CO2 Concentration (ppm) | Temperature (°C) |
| — | — | — |
| T1 | 10 | 200 | 15 |
| T2 | 50 | 400 | 25 |
| T3 | 100 | 800 | 35 |
| Control | 50 | 400 | 25 |

Expected Outcomes:

• Light Intensity:
  • Increasing light intensity will increase the rate of photosynthesis up to a point (light saturation).
  • Decreasing light intensity will decrease the rate of photosynthesis.
• CO2 Concentration:
  • Increasing CO2 concentration will increase the rate of photosynthesis.
  • Decreasing CO2 concentration will decrease the rate of photosynthesis.
• Temperature:
  • Optimal temperature for photosynthesis varies among species (typically between 20-30°C).
  • Temperatures above or below the optimum will decrease the rate of photosynthesis.

Example Calculations and Graphs:

• Rate of Photosynthesis (μmol CO2/m² s):
  = (Net CO2 uptake – Respiration) / (Leaf area x time)
• Growth Rate (e.g., biomass increase over time):
  = (ΔBiomass / ΔTime)

Graphical Representation:

• Rate of Photosynthesis vs. Light Intensity:
  • A curve showing the effect of increasing light intensity on the rate of photosynthesis.
• Rate of Photosynthesis vs. CO2 Concentration:
  • A curve illustrating the effect of increasing CO2 concentration on the rate of photosynthesis.
• Growth Rate vs. Temperature:
  • A curve showing the effect of temperature on growth rate (e.g., biomass increase over time).