Which plant hormone is known as the 'stress hormone' and promotes seed dormancy?
A. Abscisic acid (ABA)
B. Cytokinin
C. Gibberellin
D. Ethylene
Answer: Option A
Solution (By JKSSB Mock Tests)
Abscisic acid (ABA) is called the stress hormone because it accumulates under adverse conditions (drought, cold) and triggers adaptive responses like stomatal closure. It also promotes seed dormancy and inhibits germination. Gibberellins break seed dormancy, cytokinins promote cell division, ethylene promotes fruit ripening. ABA is antagonistic to gibberellins.
Explanation:
Anabaena azollae is a heterocystous cyanobacterium that lives symbiotically in the dorsal leaf cavities of the water fern Azolla. It fixes atmospheric nitrogen, providing a natural nitrogen source for rice paddies when Azolla is used as green manure. Nostoc is free-living or lichen symbiont, Rhizobium and Azotobacter are bacteria.
Consider the following statements regarding photosynthesis:
1. Light reactions occur in the thylakoid membranes.
2. Oxygen is released from carbon dioxide.
3. ATP and NADPH are produced in the light reactions.
Which of the above is/are correct?
Explanation:
Light reactions occur in thylakoid membranes, producing ATP, NADPH, and oxygen. Oxygen comes from water (photolysis), not CO₂. So statement 2 is incorrect. 1 and 3 are correct.
Explanation:
The colon (large intestine) primarily absorbs water, sodium, and some vitamins (produced by gut flora) from the indigestible food residue, converting it into semisolid feces. It does not secrete digestive enzymes; that is the small intestine's role. Protein digestion and amino acid absorption occur in the small intestine.
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