Photosynthesis Adaptations Flashcards
Factors affecting rate of photosynthesis
- light intensity
- temperature
- CO2 concentration
- O2 concentration
- colour of light
How can rate of photosynthesis be measured?
from rate of gas exchange between the green plant and its surrounding environment (O2 produce, CO2 uptake)
Light intensity
- at low intensity as light increases, photosynthesis increases
- at high light intensity, rate determined by other factores
Temperature
- at temp increase, rxn rate increase up to point (increase Ek)
- past 50C enzymes denature so no photosynthesis
- at temp increase, rate of photo resp increase, so rate increased is lower (slower)
CO2 concentration
at CO2 increase, photosynthesis increase (more CO2 for Calvin cycle)
O2 concentration
as O2 increase, photosynthesis decrease (more photorespiration. (O2 competes with CO2 for Rubisco)
Colour of light
- green, reflected, no absorbed, therefore decrease photosynthesis
- red + blue, absorbed, therefore increase photosynthesis
Why do graphs level off?
reach a certain point, particular enzymes will only work so fast in those conditions. Rubisco can’t work at that level
Side effect of plants closing their stomata on hot days to conserve water? Results in?
CO2 can’t enter, O2 can’t exit. Results in photorespiration (Rubisco accepts O2 in place of CO2)
What does photorespiration result in?
Oxidation of RuBP instead of its carboxylation to PGA (called photorespiration because is occurs in light)
How does photorespiration affect the production of carbohydrates by photsynthesis?
decreases production of carbohydrates, decreases photosynthesis rate by removing carbon from cycle.
C4 Plants
seperate the uptake of CO2 from Calvin cycles
CAM Plants
trap CO2 at day, release it during the night to higher concentration
Open stomata at night to obtain sunlight during day
