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Photosynthesis Lab. Background. How can we measure the rate of photosynthesis? Reaction. Background. Leaf histology: Two cell layers that are responsible for photosynthesis Palisade mesophyll: closely stacked Spongy mesophyll: spacious, why?
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Background • How can we measure the rate of photosynthesis? • Reaction
Background Leaf histology: • Two cell layers that are responsible for photosynthesis • Palisade mesophyll: closely stacked • Spongy mesophyll: spacious, why? • Based the anatomy on this diagram, classify the type of plant. Justify your response
Floating Disk Technique: • Leaf disks float b/c of air spaces in the spongy mesophyll • When these spaces are infiltrated with a solution of CO2 , their density increases and they sink. • As photosynthesis occurs O2 is produced, which increases the buoyancy of the disk causing it to rise. • What does this technique measure in photosynthesis?
Procedure Materials
Data Collection and Analysis Raw data: We will count the number of floating leaf disks every 30 sec. until all disks are floating. Dependant Variable: ET50: The point at which the median (50%) number of disks are floating. • The ET50 of the example would be 11.5 min. Example experiment: How does light intensity affect the rate of photosynthesis?
Data Collection and Analysis Problem with the ET50: • The value goes down as the rate of photosynthesis goes up. (see example graph) • How can we mathematically solve this problem, to show a direct correlation.
Data Collection and Analysis Calculate the inverse of the ET50 or 1/ET50 Ex: ET50 for 200FT-C = 20 So 1/ET50 for 200FT-C = .05 When all data has been converted the proper direct relationship b/w light intensity and photosynthetic rate will be shown. (see graph)
What affects the rate of photosynthesis? Abiotic Biotic