Question

Which hormone causes stunted growth in pea?
A.Gibberellic acid
B.Auxin
C.Cytokinin
D.Ethylene

Answer 1

Growth hormones are defined as organic substances which are synthesized in minute quantities in one part of the plant body and transported to another part where they influence specific physiological processes.
A group of plant hormones including auxins, gibberellins, cytokinins , ethylene and abscisic acids are presently known to regulate growth.

Complete answer:
-Auxin include all chemical substances which promote growth of stem or coleoptiles section
Gibberlines are the plant growth hormones which enhance the longitudinal growth of stem when applied to intact plants. The presence of meristematic cells is necessary for the elongation growth caused by them.
-The cytokinins are plant growth substances which act primarily on cell division and have little or no effect on extension growth.
-Ethylene prevents elongation of stem and roots in longitudinal direction however the inhibition of growth in length is associated with radial enlargement of the tissue.

So, the correct answer is D. Ethylene

Note:
-Abscisic acid which is also a growth hormone which inhibits growth and induces bud dormancy.
-Ethylene also causes suppression of bud growth and causes apical dominance
-The growth of fruit is stimulated by ethylene
-Ethylene stimulates the formation of a separation layer or abscission zone in leaves, flowers and fruits
-Ethylene stimulates rooting of cuttings, initiation of lateral roots and growth of root hair
-The other three growth hormones are growth promoters whereas ethylene is growth inhibitor