Which one among the following is not a plant hormone ?
- A.Gibberellins
- B.Abscisic acid
- C.Auxins
- D.Thyroxine
Correct answer
Explanation
The correct answer is D, Thyroxine. Thyroxine is an animal hormone, made by the thyroid gland in the neck, and it controls the rate of metabolism in the human body. Iodine is needed to make it, which is why a lack of iodine causes goitre. Plants have their own growth regulators, called phytohormones, and the five main ones are auxins, gibberellins, cytokinins, abscisic acid and ethylene. Option A is wrong because gibberellins are plant hormones that lengthen stems, break seed dormancy and are used to enlarge grapes. Option B is wrong because abscisic acid is a plant hormone that closes stomata during drought and keeps seeds and buds dormant, earning it the name 'stress hormone'. Option C is wrong because auxins are plant hormones that cause cell elongation and make shoots bend towards light. Exam tip: auxin, gibberellin, cytokinin = growth promoters; abscisic acid and ethylene = inhibitors and ripening; thyroxine belongs to animals.
Practice Questions
View allWhich one of the following is monatomic?
- A.Hydrogen
- B.Sulphur
- C.Phosphorus
- D.Helium
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Read the full explanation →The normal systolic pressure in human beings is :
- A.80 mm of Hg
- B.100 mm of Hg
- C.120 mm of Hg
- D.140 mm of Hg
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- A.Archaeologists
- B.Anthropologists
- C.Palaeontologists
- D.Geologists
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Read the full explanation →Which of the following catalytic systems is used for the reduction of unsaturated hydrocarbon to saturated hydrocarbon?
- A.Copper and H2
- B.Iron and H2
- C.Zinc and H2
- D.Nickel and H2
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Read the full explanation →A chemical that donates a proton (hydrogen ion) is called
- A.Hydrophilic
- B.Protophilic
- C.Hydrophobic
- D.Acid
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In the Brønsted–Lowry theory an acid is any substance that gives away a proton, that is a hydrogen ion (H⁺), to another substance.
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