IGCSE Study Buddy: Biology - Plant Nutrition (Part 2)
Overview
- Focus on photosynthesis in plants
- Importance of chlorophyll, light, and carbon dioxide
- Investigations to prove necessity of these factors
- Explore factors affecting rate of photosynthesis
Importance of Key Factors
Chlorophyll
- Absorbs light crucial for photosynthesis
- Converts light energy into chemical energy
- Investigated using variegated leaves which have both chlorophyll-containing and non-chlorophyll areas
Light
- Provides energy for photosynthesis
- Investigated by covering parts of a leaf and exposing it to sunlight
Carbon Dioxide
- Converted into sugars like glucose during photosynthesis
- Investigated using bell jars with sodium hydroxide (absorbs CO2) and water as a control
Investigations on Photosynthesis
Starch Test
- Reliable indicator of photosynthesis occurrence
- Glucose rapidly converted and not reliable for testing
Preparing Leaves for Starch Test
- Destarch plants by leaving them in the dark for 48 hours
- Boil leaves in water to make them permeable
- Boil leaves in ethanol to decolorize and remove chlorophyll
- Rinse leaves in water to soften them
- Test with iodine solution: blue-black indicates starch presence
Investigations
Need for Chlorophyll
- Use variegated leaves
- Only green areas (with chlorophyll) turn blue-black after iodine test
Need for Light
- Cover parts of leaves with foil
- Exposed areas turn blue-black after iodine test, indicating photosynthesis
Need for Carbon Dioxide
- Use bell jars with sodium hydroxide and water
- Leaves near water turn blue-black, others remain iodine color
Factors Affecting Rate of Photosynthesis
Light Intensity
- Setup involves aquatic plant, beaker, sodium hydrogen carbonate, funnel, and thermometer
- Increase light intensity to boost photosynthesis until another factor limits
Carbon Dioxide Concentration
- Similar setup
- Vary sodium hydrogen carbonate concentration
- Increase CO2 boosts photosynthesis until limited by other factors
Temperature
- Similar setup
- Use hot plate to vary temperature
- Rate increases with temperature until enzymes denature
Conclusion
- Photosynthesis is dependent on chlorophyll, light, and carbon dioxide
- Rate is affected by light intensity, CO2 concentration, and temperature
- Understanding these factors is crucial for studying plant nutrition.
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