1. What is the main effect of gibberellins on the stems of many plants?
A.
They promote stem elongation
B.
They stop cell division
C.
They cause stem tissues to dry
D.
They prevent internode growth
Correct Answer:
They promote stem elongation
Explanation:
Gibberellins promote stem elongation by stimulating the growth of cells, especially in the internodes.
2. Which part of a plant stem usually becomes longer due to gibberellin action?
A.
Internodes
B.
Root hairs
C.
Leaf veins
D.
Seed coats
Correct Answer:
Internodes
Explanation:
Gibberellins increase the length of internodes, the regions between two successive nodes of a stem.
3. Gibberellins increase stem length mainly by promoting:
A.
Cell elongation
B.
Cell death
C.
Water loss from leaves
D.
Formation of root caps
Correct Answer:
Cell elongation
Explanation:
Stem elongation occurs because gibberellins stimulate the elongation of cells in growing stem regions.
4. The rapid elongation of the stem before flowering in some plants is called:
A.
Bolting
B.
Germination
C.
Transpiration
D.
Pollination
Correct Answer:
Bolting
Explanation:
Bolting is the rapid elongation of the stem, often seen before flowering, and gibberellins can promote this process.
5. Which plant growth regulator is commonly used to increase the length of stems?
A.
Gibberellin
B.
Abscisic acid
C.
Ethylene
D.
Cytokinin
Correct Answer:
Gibberellin
Explanation:
Gibberellins are widely known for promoting stem and internode elongation.
6. A dwarf plant may become taller after treatment with gibberellin because gibberellin promotes:
A.
Stem elongation
B.
Leaf fall
C.
Fruit decay
D.
Root shrinkage
Correct Answer:
Stem elongation
Explanation:
Gibberellin treatment can increase the length of stems and may partially overcome genetic dwarfness in some plants.
7. What visible change is most likely after applying gibberellin to a suitable young stem?
A.
Longer internodes
B.
Shorter internodes
C.
Complete loss of nodes
D.
Immediate stem bending
Correct Answer:
Longer internodes
Explanation:
Gibberellin promotes elongation of the internodal regions, making the stem longer.
8. Gibberellin-induced stem elongation is especially noticeable in:
A.
Young growing stems
B.
Dead stems
C.
Fully dried stems
D.
Removed bark only
Correct Answer:
Young growing stems
Explanation:
Gibberellins act most effectively on actively growing stem tissues, where cells can elongate.
9. If gibberellin activity increases in a plant stem, the distance between adjacent nodes generally:
A.
Increases
B.
Disappears
C.
Remains absent
D.
Changes into a root
Correct Answer:
Increases
Explanation:
Gibberellins increase internode length, so the distance between adjacent nodes becomes greater.
10. Why are gibberellins useful in producing taller plants?
A.
They stimulate elongation of stem cells
B.
They remove all leaves
C.
They stop stem growth
D.
They destroy the growing regions
Correct Answer:
They stimulate elongation of stem cells
Explanation:
Gibberellins make plants taller mainly by stimulating the elongation of cells in the stem and internodes.
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