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A researcher is studying a C4 plant under controlled conditions. They suddenly increase the oxygen concentration in the environment while maintaining constant light and CO2 levels. Which of the following is the MOST likely immediate consequence?
A significant decrease in the rate of photosynthesis
A slight increase in photorespiration
A significant increase in the rate of photosynthesis
No change in the rate of photosynthesis or photorespiration
In a hypothetical experiment, a scientist genetically modifies a C4 plant to lack PEP carboxylase. Which of the following would be the MOST likely outcome under normal atmospheric conditions?
The plant would switch to CAM photosynthesis.
The plant would exhibit significantly reduced CO2 fixation and increased photorespiration.
CO2 fixation would remain unchanged, but the plant would require more water.
The plant would grow more efficiently due to reduced energy expenditure in the C4 pathway.
A plant is exposed to an environment with high CO2 and low O2 concentrations. Which process would be MOST directly and significantly inhibited under these conditions?
Calvin cycle
Photorespiration
Electron transport chain
C4 cycle
Under conditions of high temperature and light intensity, why do C4 plants show higher photosynthetic rates compared to C3 plants?
C4 plants have a higher affinity for CO2 than C3 plants.
C4 plants open their stomata more frequently than C3 plants.
C4 plants can utilize a wider range of light wavelengths compared to C3 plants.
Spatial separation of initial CO2 fixation and the Calvin cycle minimizes photorespiration.
Under conditions of high temperature and drought stress, a plant closes its stomata to conserve water. Which of the following is the MOST DIRECT consequence on the Calvin cycle?
Increased photorespiration due to oxygen accumulation.
Enhanced ATP synthesis due to increased proton gradient.
Reduced availability of CO2 limits carboxylation, leading to a decrease in RuBP regeneration.
Increased activity of Rubisco due to higher substrate concentration.
Which of the following combinations of factors would MOST SIGNIFICANTLY limit the rate of photosynthesis in a typical C3 plant?
Low light intensity, high CO2 concentration, and optimal temperature
High light intensity, low O2 concentration, and high humidity
High temperature, low CO2 concentration, and water stress
Low temperature, high CO2 concentration, and waterlogged soil
Which of the following is NOT a characteristic of C4 plants?
High CO2 compensation point
Kranz anatomy
Presence of PEP carboxylase
Dimorphic chloroplasts
PEP carboxylase
I. is involved in atleast some fixation in both and plants
II. Catalyses the reaction of fixing into pyruvic acid in bundle sheath cells
III. is capable of fixing more efficiently at lower atmospheric concentration than RuBP carboxylase
Select the correct option
I and II
I and III
II and III
I, II and III
I. Initial acceptor
II. Extent of photorespiration
III. Enzyme catalysing reaction that fixes
IV. Presence of Calvin cycle
V. Leaf anatomy
Which one does not differ in a and plants?
I and V
Only IV
II and III
Only II
The first product of fixation in pathway is
Oxaloacetic acid
RuBP
PGA
Inorganic acid
