Question

Which one of the following pairs is not correctly matched?
A.Abscisic acid – Stomatal closure
B.Gibberellic acid – Leaf fall
C.Cytokinin – Cell division
D.IAA – Cell elongation

Answer 1

Abscisic acid, Gibberellic acid, Cytokines and IAA (indole Acetic Acid) all are the phytohormones also called as the plant hormones. Phytohormones are the signal molecules that occur in extremely low concentrations. Plant hormones are responsible for the plant growth and plant development, pathogen defense, stress tolerance, etc. They are the small organic molecules.

Complete answer:
Abscisic acid:
Abscisic acid was discovered by F.T. Addicott and his associates in the early 1960s.
Abscisic acid is found in the leaves, stems and green fruits.
Functions of the abscisic acid include closure of stomata, bud dormancy, seed dormancy, inhibits shot growth, etc. This hormone is important for plants in response to many environmental stresses like soil salinity, drought, cold stresses, heat stress, etc.
Gibberellic acid:
Gibberellic acid is also called as the gibberellin A3, GA and GA3.
When gibberellic acid is purified, it is a white to pale yellow solid.
Gibberellic acid is a pentacyclic diterpene acid. Gibberellic acid promotes the growth and elongation of the plant cells.
Gibberellic acid also stimulates rapid stem and root growth, induce mitotic division in the leaves of some plants and increase seed germination rates. Gibberellic acid is also used in laboratories in order to trigger germination in seeds.
Cytokinin:
Cytokinin promotes cell division or cytokinesis in plant roots and shoots.
Cytokinin are primarily invo;lved in the cell growth and differentiation. Cytokinin alos affects apical dominance, axillary bud growth and leaf senescence.
There are two types of cytokines-
Adenine type cytokinins – Kinetin, zeatin and 6-benzylaminopurine.
Phenylurea type cytokines – diphenylurea, Thidiazuron.
IAA (Indole Acetic acid):
Indole acetic acid is a plant hormone that belongs to the class of auxins.
Indole acetic acid is a derivative of indole.
It is colourless solid which is soluble in the polar organic solvents.
Indole acetic acid has many effects such as cell elongation and cell divisions.
This hormone acts as a signaling molecule for the development of the plant organs and coordination of the growth.
Therefore, it has been clear from the above discussion that all the pairs are correctly matched except one i.e. gibberellic acid – leaf fall.
Hence the correct answer is option(B)

Note: Apart from the above discussed plant hormones Ethylene is also a plant hormone. Ethylene is a first identified plant hormone. Ethylene is an unsaturated carbon compound which naturally acts as a plant hormone. It is a multifunctional hormone that regulates both growth and senescence.
Functions of Ethylene:
a.Stimulating the fruit ripening
b.Increases the speed of leaf and flower senescence
c.Induces flowering
d.Inhibits stem growth
e.Induces root growth in order to absorb more and more water
f.Helps in determining the sex of a flower.
g.Helps in root initiation and pollination.