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Mixed statements: plant physiology and anatomy
Concepts tested here
- Chemiosmosis
All Questions
2012 AIPMT-MAINS 1 question
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Read the following four statements (A – D).
(A) Both photophosphorylation and oxidative phosphorylation involve uphill transport of protons across the membrane
(B) In dicot stems, a new cambium originates from cells of pericycle at the time of secondary growth
(C) Stamens in flowers of $Gloriosa$ and $Petunia$ are polyandrous
(D) Symbiotic nitrogen-fixers occur in free-living state also in soil
How many of the above statements are right?(A) is right: in both chloroplasts and mitochondria, the energy of electron transport is used to pump protons across the membrane against their concentration gradient (uphill), and the resulting proton gradient drives ATP synthesis.
(B) is wrong: in dicot stems the new (interfascicular) cambium arises from the cells of the medullary rays lying between the vascular bundles. A cambium originating from the pericycle is a feature of dicot roots.
(C) is not accepted as right: the stamens of $Petunia$ (Solanaceae) are epipetalous, i.e., attached to the petals, so the two plants cannot be described together simply as polyandrous.
(D) is right: symbiotic nitrogen fixers such as $Rhizobium$ live freely in the soil as aerobes and enter the symbiotic association only when they infect the roots of a legume.
Statements (A) and (D) are right, so two statements are right.