Question: 137. Spraying sugarcane crop with which of the following plant growth regulators, increases the length of stem, thus, increasing the yield?
(1) Auxin
(2) Gibberellin
(3) Cytokinin
(4) Abscisic acid
Answer: Option (2)
Explanation:
Gibberellins are plant growth regulators that promote stem elongation by increasing both cell division and cell elongation in the internodal regions.
In sugarcane, spraying gibberellin enhances the length of the stem by elongating the internodes,
which directly increases the overall yield of the crop.
Auxins mainly promote cell elongation in shoots but are not specifically used to increase internodal length in sugarcane.
Cytokinins primarily stimulate cell division and delay senescence but do not significantly increase stem length.
Abscisic acid is a growth inhibitor and does not promote stem elongation.
Therefore, spraying sugarcane with gibberellin increases stem length and yield.