Photosynthesis in Higher Plants

Which 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.

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.