Which one of the following tissues is responsible for increase of girth in the stem of a plant?
- A.Tracheid
- B.Pericycle
- C.Intercalary meristem
- D.Lateral meristem
Correct answer
Explanation
The correct answer is D, Lateral meristem. Lateral meristems divide along the sides of the stem and root and add new cells that make them thicker.
Meristems are groups of cells that keep dividing. Apical meristems at the tips of the stem and root increase length, which is primary growth. Lateral meristems, namely the vascular cambium and the cork cambium, run along the length of the organ and cause secondary growth, that is, an increase in girth. The vascular cambium adds secondary xylem inside and secondary phloem outside each year, and in trees this forms the annual rings used to estimate age, while the cork cambium forms the bark.
Option A is wrong because tracheids are dead, water-conducting cells of the xylem and do not divide. Option B is wrong because the pericycle is the layer from which lateral roots arise. Option C is wrong because the intercalary meristem, found at the internodes of grasses, adds length.
Exam tip: apical meristem = length, lateral meristem (cambium) = girth, intercalary meristem = internode length.
Practice Questions
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- C.4, 5
- D.3, 5
Show answer
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- D.Ascomycetes, a saprophytic fungi is multicellular or rarely unicellular
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- B.smaller than osmotic pressure
- C.equal to osmotic pressure
- D.equal to atmospheric pressure
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- A.Magnesium
- B.Lead
- C.Tin
- D.Silver
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Read the full explanation →The foul smell of urine of a healthy man having healthy food, when spilled on floor, is mainly due to the bacterial decomposition of
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- B.sugar into carbon dioxide
- C.lipids into methane
- D.urea into ammonia
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