Plants deficient of element zinc, show its effect on the biosynthesis of plant growth hormone:

Step-by-step solution

Chemically auxins are weakly acidic growth hormones that have an unsaturated ring structure. They are capable of promoting cell elongation, especially of shoots but are inhibitory to the roots. Zinc is involved in the synthesis of Indoleacetic acid in plants and act as an activator in the enzyme tryptophan synthetase. Tryptophan is the precursor of Indole-acetic acid. Related Theory Antiauxins are a group of chemicals that can prevent auxin-action in plants. Transcinnamic acid, ascorbic acid, 7-phenyl butyric acid