Multiple Choice QuestionsWhich of the following statements is correct
Photorespiration is useful process.
C4 plants are more efficient than C3 plants.
C3 plants are more efficient than C4 plants.
Photorespiration is absent in C3 plants but present in C4 plants.
Which of the following is the characteristic of PS-I?
It is active only upto 680 nm of light.
The reaction centre of PS- I is P680.
PS- I is reduced by the electrons released in photolysis of water.
PS-I is involved in non-cyclic photophosphorylation.
Assertion : Dark reaction occurs only at night in the stroma of chloroplast.
Reason : CO2 fixation occurs only during C3 cycle.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
In succulent plants the stomata open in night and close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only.
CO2 accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.
Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.
Low CO2 concentration accumulates organic acids resulting in the increased concentration of cell sap.
CO2 used up, increase pH results in accumulation of sugars.
B.
Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.
In CAM plants stomata open at night. In these plants night acidification occurs. i.e., malic acid is
synthesised during night due to incomplete oxidation of carbohydrates.
In night. 2 C 6H12O6+ 3 O2 3 C 4H6O5+ 3H2O
(malic acid)
leads to opening of stomata
At night malic acid formed in guard cells dissociates into H and malate ions. K ion exchange from subsidiary cells with H ions. Thus due to accumulation of K ions osmotic pressure of guard cells increases, endosmosis occurs and guard cells become turgid due to which stomata opens. The malic acid at clay time breaks into CO2 and pyruvic acid thus increasing the concentration of CO2 in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.
Chlorenchyma is known to develop in the
cytoplasm of Chlorella
mycelium of a green mould such as Aspergillus
spore capsule of a moss
pollen tube of Pinus
Velamen present in orchids helps in
absorption of nutrients from host plant
respiration
absorption of moisture from air
synthesising food
Assertion: The higher concentration of O2 in the atmosphere is inhibitory to photosynthesis.
Reason: CO2 is the main substrate of photosynthesis.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
Assertion : Dark reaction is purely enzymatic reaction.
Reason : It occurs only in absence of light.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
What is common between chloroplasts, chromoplasts and leucoplasts
Presence of pigments
Possession of thylakoids and grana
Storage of starch, proteins and lipids
Ability to multiply by a fission-like process
Assertion: Under conditions of high light intensity and limited CO2 supply,
photorespiration has a useful role in protecting the plants from photo-oxidative damage.
Reason: If enough CO2 is not available to utilize light energy for carboxylation to proceed, the excess energy may not cause damage to plants.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
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