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Questions and Answers
What does the rate of net photosynthesis represent?
What does the rate of net photosynthesis represent?
- Total carbon assimilation in plants
- Only the rate of CO2 loss
- Total energy conversion efficiency
- Difference between carbon assimilation and CO2 loss (correct)
Which environmental factor directly affects photosynthesis according to the document?
Which environmental factor directly affects photosynthesis according to the document?
- Ambient CO2 concentrations (correct)
- Soil nutrients
- Presence of herbivores
- Atmospheric pressure
What hypothesis did F.F. Blackman propose regarding photosynthesis?
What hypothesis did F.F. Blackman propose regarding photosynthesis?
- Photosynthesis is unlimited under optimal conditions.
- Photosynthesis is always limited by light availability.
- Photosynthesis can be limited by multiple factors simultaneously.
- The slowest step in the process limits the rate of photosynthesis. (correct)
Why is understanding photosynthesis important to agronomists?
Why is understanding photosynthesis important to agronomists?
Which of the following is not mentioned as an indirect environmental factor affecting photosynthesis?
Which of the following is not mentioned as an indirect environmental factor affecting photosynthesis?
What aspect of photosynthesis is of great interest to ecologists?
What aspect of photosynthesis is of great interest to ecologists?
What does the term 'limiting factor' refer to in photosynthesis?
What does the term 'limiting factor' refer to in photosynthesis?
Which of the following is NOT a physiological variable affecting photosynthesis?
Which of the following is NOT a physiological variable affecting photosynthesis?
What is the main effect of dynamic photoinhibition under moderate excess light?
What is the main effect of dynamic photoinhibition under moderate excess light?
Which factor influences chronic photoinhibition in intact leaves?
Which factor influences chronic photoinhibition in intact leaves?
Which of the following describes chronic photoinhibition?
Which of the following describes chronic photoinhibition?
Under which conditions is dynamic photoinhibition most likely to occur?
Under which conditions is dynamic photoinhibition most likely to occur?
How does dynamic photoinhibition affect carbon fixation?
How does dynamic photoinhibition affect carbon fixation?
What climatic condition intensifies chronic photoinhibition?
What climatic condition intensifies chronic photoinhibition?
What type of photoinhibition appears to be a daily occurrence?
What type of photoinhibition appears to be a daily occurrence?
What is observed in leaves when photoinhibition occurs under favorable environmental conditions?
What is observed in leaves when photoinhibition occurs under favorable environmental conditions?
What effect does high light intensity have on biomass production in crops?
What effect does high light intensity have on biomass production in crops?
Which xanthophyll is the most effective for heat dissipation?
Which xanthophyll is the most effective for heat dissipation?
What must leaves do when exposed to excess light energy?
What must leaves do when exposed to excess light energy?
How many aromatic rings in violaxanthin have a bound oxygen atom?
How many aromatic rings in violaxanthin have a bound oxygen atom?
What is the relative effectiveness of antheraxanthin in heat dissipation compared to zeaxanthin?
What is the relative effectiveness of antheraxanthin in heat dissipation compared to zeaxanthin?
What happens to violaxanthin under high light conditions?
What happens to violaxanthin under high light conditions?
At what PPFD level can a shade plant maximize photosynthetic oxygen evolution?
At what PPFD level can a shade plant maximize photosynthetic oxygen evolution?
In which xanthophyll does neither of the aromatic rings have a bound oxygen atom?
In which xanthophyll does neither of the aromatic rings have a bound oxygen atom?
What is the maximum photosynthetic CO2 assimilation rate observed for Atriplex triangularis grown in full sun conditions?
What is the maximum photosynthetic CO2 assimilation rate observed for Atriplex triangularis grown in full sun conditions?
How does photosynthesis in Atriplex triangularis compare between plants grown in sun and shade at low PPFD levels?
How does photosynthesis in Atriplex triangularis compare between plants grown in sun and shade at low PPFD levels?
What does PPFD stand for in the context of photosynthesis?
What does PPFD stand for in the context of photosynthesis?
At what PPFD level does Atriplex triangularis reach its peak photosynthetic CO2 assimilation when grown in the shade?
At what PPFD level does Atriplex triangularis reach its peak photosynthetic CO2 assimilation when grown in the shade?
What is likely to happen to photosynthetic activity in Atriplex triangularis as PPFD increases beyond optimal levels?
What is likely to happen to photosynthetic activity in Atriplex triangularis as PPFD increases beyond optimal levels?
What can be inferred about the light-response curve of Atriplex triangularis grown in sun conditions compared to those in shade?
What can be inferred about the light-response curve of Atriplex triangularis grown in sun conditions compared to those in shade?
In the context of photosynthesis, what does an increase in PPFD typically lead to in Atriplex triangularis?
In the context of photosynthesis, what does an increase in PPFD typically lead to in Atriplex triangularis?
Which factor likely affects the ability of Atriplex triangularis to perform photosynthesis in shaded conditions?
Which factor likely affects the ability of Atriplex triangularis to perform photosynthesis in shaded conditions?
What year did C. David Keeling begin systematic measurements of CO2 at Mauna Loa?
What year did C. David Keeling begin systematic measurements of CO2 at Mauna Loa?
What is the predicted atmospheric CO2 concentration by the year 2100 if current emissions continue?
What is the predicted atmospheric CO2 concentration by the year 2100 if current emissions continue?
What primarily influences the diffusion rate of CO2 into the leaf?
What primarily influences the diffusion rate of CO2 into the leaf?
What is the main entry point for CO2 into the leaf?
What is the main entry point for CO2 into the leaf?
What happens to water vapor as CO2 diffuses into the leaf?
What happens to water vapor as CO2 diffuses into the leaf?
Since 1958, by more than what percentage have atmospheric CO2 concentrations increased?
Since 1958, by more than what percentage have atmospheric CO2 concentrations increased?
Which process is essential for photosynthesis in relation to CO2?
Which process is essential for photosynthesis in relation to CO2?
What factor does the impermeability of the cuticle affect regarding CO2 and H2O?
What factor does the impermeability of the cuticle affect regarding CO2 and H2O?
Study Notes
Photosynthesis: Physiological and Ecological Considerations
- Chapter focuses on the photosynthetic responses of the leaf to its environment
- Net photosynthesis: The difference between photosynthetic carbon assimilation and CO2 loss via respiration
- Factors influencing photosynthesis: Light, CO2 concentrations, temperature, humidity and soil moisture
- Agronomists study photosynthetic variation to improve crop yield
- Blackman’s Limiting Factor Hypothesis: This hypothesis proposes that at any given moment, the rate of photosynthesis is constrained by the most limiting factor, which can be light intensity, carbon dioxide concentration, or temperature. When one of these factors is insufficient, it can restrict the photosynthetic process, regardless of the abundance of other factors. A single factor can limit photosynthetic rate, such as light or CO2 concentration
- Sun Plants: Atriplex triangularis, commonly known as saltbush, is particularly well adapted to environments with intense sunlight. When cultivated under conditions of elevated light intensity, these plants exhibit markedly increased rates of photosynthesis. This enhanced capability allows them to efficiently convert light energy into chemical energy, supporting their growth and survival in arid and saline conditions.
- Shade Plants: Adaptations to low light conditions, including lower photosynthetic capacity and thicker leaves
- Photoinhibition: occurs when leaves are exposed to excess light
- Dynamic Photoinhibition: Decreases quantum yield without affecting maximum photosynthetic rate
- Chronic Photoinhibition: Causes damage to the chloroplast due to excess light or failed protective mechanisms
- Temperature: Optimal temperature range for photosynthesis varies between species and is significantly affected by light intensity and CO2 concentration
- CO2 Concentration Increase: Since 1958, atmospheric CO2 concentration has increased by over 25%, reaching 600-750ppm by 2100 if emissions aren't reduced.
- C3 Plants: Benefit from higher CO2 levels due to Rubisco’s increased activity
- C4 Plants: Show a smaller response to elevated CO2 levels, which reduces the difference in photosynthetic rates between C3 and C4 plants
- CO2 Diffusion: Essential for photosynthesis. CO2 diffuses from the atmosphere through the leaf, into the substomatal cavity, and finally to the carboxylation site of Rubisco.
- Diffusion Rate: Depends on the CO2 concentration gradient and resistances along the diffusion pathway.
- Stomata: Main entry point for CO2 into the leaf. The pathway for CO2 diffusion is also used by H2O for transpiration.
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Description
This quiz covers key concepts related to photosynthesis, focusing on how environmental factors influence leaf responses. Topics include the net photosynthesis calculations, Blackman’s Limiting Factor Hypothesis, adaptations of sun and shade plants, and the effects of photoinhibition. Perfect for understanding the physiological and ecological aspects of plant biology.
