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Flashcards from PDF
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1
Question
What is net photosynthesis and how is it calculated?
Answer
Net photosynthesis is the increase or decrease of gross (true) photosynthesis minus photorespiration and dark respiration. It is calculated as: Net Photosynthesis = Gross Photosynthesis - Dark Respiration.
2
Question
What comprises gross photosynthesis?
Answer
Gross photosynthesis comprises both light and dark reactions of photosynthesis.
3
Question
What is dark respiration in plants?
Answer
Dark respiration refers to mitochondrial respiration processes, both aerobic and anaerobic, which consume oxygen and release carbon dioxide.
4
Question
Why is maintaining a positive carbon balance important for plants?
Answer
Maintaining a positive carbon balance is essential for plants to survive, grow, and reproduce because carbon gained from photosynthesis must exceed that lost through respiration.
5
Question
What factors influence how plants allocate carbon gained from photosynthesis?
Answer
Carbon allocation is influenced by environmental conditions, light availability, and the need to balance growth, survival, and reproduction, including whether the plant is sun-adapted or shade-adapted.
6
Question
How does light availability affect carbon allocation to leaf tissue?
Answer
Under ideal conditions, plants allocate more carbon to leaf tissue to increase photosynthetic surface area, especially when exposed to less sunlight, to promote faster growth.
7
Question
Explain the overall carbon balance equation for a plant.
Answer
The total carbon balance considers CO₂ uptake in photosynthesis per leaf area multiplied by total leaf surface area, minus CO₂ loss through respiration multiplied by total mass of living tissue.
8
Question
What role does rubisco play in plants and why is it significant?
Answer
Rubisco catalyzes the start of the Calvin Cycle in photosynthesis and is a costly molecule for plants to manufacture. It accounts for about 40% of protein in chloroplasts and is likely the most abundant protein on Earth.
9
Question
What is phenotypic plasticity in relation to plant responses to light?
Answer
Phenotypic plasticity is the ability of individuals of the same species to exhibit different photosynthetic and morphological traits when grown under different light conditions.
10
Question
How are shade-intolerant and shade-tolerant plants adapted differently?
Answer
Shade-intolerant (sun-adapted) plants are adapted to high-light environments, whereas shade-tolerant plants are adapted to low-light environments, showing differences in physiological and morphological traits.
11
Question
How do terrestrial and aquatic plants exchange heat to maintain energy balance?
Answer
Terrestrial plants exchange heat primarily through convection and evaporation, while aquatic plants mainly rely on convection to maintain positive net photosynthesis.
12
Question
What is photosynthetically active radiation (PAR) and why is it important for plants?
Answer
PAR is the portion of sunlight that plants can use for photosynthesis. Its availability greatly influences plant growth and carbon balance, especially under competition with other plants.
13
Question
How does the presence of other plants influence individual plant access to PAR?
Answer
Other plants affect the amount of PAR available to each plant, creating trade-offs in resource access and affecting their photosynthesis and growth strategies.
14
Question
Describe the relationship between plant temperature and energy balance with the environment.
Answer
Plant temperature reflects their energy balance as they absorb radiation that powers metabolic processes and heats leaves and surrounding air; plants must exchange heat (via convection and evaporation) with the environment to maintain photosynthesis.
15
Question
Why is measuring oxygen release or carbon dioxide uptake important in studying plant respiration and photosynthesis?
Answer
Measuring oxygen release or CO₂ uptake provides direct information about the rates of photosynthesis and respiration, indicating the plant's net carbon gain or loss.
16
Question
How do seedlings grown under low light conditions differ in terms of respiration and photosynthesis?
Answer
They have a lower rate of respiration, decreased light compensation point, and decreased maximum rate of net photosynthesis at light saturation.
17
Question
What morphological changes occur in seedlings grown under low light conditions?
Answer
They develop larger and thinner leaves (greater specific leaf area) and allocate more carbon to leaf production and less to roots.
18
Question
What was the focus of Stuart Davies' greenhouse experiments with Macaranga seedlings?
Answer
Studying trade-offs in leaf respiration rate, light compensation point, and maximum rate of net photosynthesis among nine species.
19
Question
What is the primary function of the C₄ carbon cycle in plants?
Answer
To prevent the cost of photorespiration (O₂ build-up) by incorporating CO₂ into four-carbon compounds in mesophyll and bundle sheath cells.
20
Question
Describe the main steps of the C₄ carbon cycle.
Answer
PEP carboxylase in mesophyll cells converts PEP to oxaloacetate (4C), which becomes malate (4C). Malate moves to bundle sheath cells, converted to pyruvate (3C), releasing CO₂ used in the Calvin cycle to produce sugars. Pyruvate returns to mesophyll cells to restart the cycle.
21
Question
Which types of plants commonly use the C₄ carbon cycle?
Answer
Plants in 16 families including monocots and dicots such as corn, millet, sugarcane, and maize.
22
Question
How does temperature relate to a plant’s water demand and adaptations?
Answer
Higher temperatures increase water demand, prompting plants to develop adaptations such as alternative photosynthetic pathways that increase water-use efficiency.
23
Question
What photosynthetic pathways have plants adapted to in warmer, drier environments to improve water-use efficiency?
Answer
The C₄ photosynthetic pathway and the CAM pathway.
24
Question
What are some plant responses to moisture stress?
Answer
Leaf curling and wilting, inhibition of chlorophyll production leading to leaf loss, drought deciduous behavior, and modified photosynthetic pathways.
25
Question
Why must plants balance the opening and closing of stomata?
Answer
Because closing stomata reduces water loss but also limits CO₂ intake and evaporative cooling, which can reduce photosynthesis and increase leaf temperatures.
26
Question
What is phenotypic plasticity in plants regarding light environments?
Answer
It is the ability of individuals of the same species to adjust their photosynthetic and morphological traits depending on different light conditions.
27
Question
How do shade-intolerant and shade-tolerant plants differ?
Answer
Shade-intolerant (sun-adapted) plants are adapted to high-light environments, while shade-tolerant (shade-adapted) plants thrive in low-light environments.
28
Question
What advantage do C₄ plants have over other plants concerning stomatal opening and water loss?
Answer
For a given stomatal opening and water loss, C₄ plants fix more carbon, resulting in greater water-use efficiency.
29
Question
In what regions are C₄ plants most commonly found?
Answer
In tropical and subtropical regions, especially among grasses.
30
Question
Compare the spatial and temporal separation of carbon fixation steps in C₄ and CAM plants.
Answer
C₄ plants separate steps spatially between mesophyll and bundle-sheath cells, while CAM plants separate steps temporally by fixing CO₂ at night and using it during the day.