Question

Plant growth regulators (PGRs) are
A. Simple organic substances of different chemical composition
B. Complex organic substance of different chemical composition
C. Simple and complex organic substance of same chemical composition
D. None

Answer 1

Hint: The plant growth regulators are also called as phytohormones. These are chemical structures produced from various parts of the plant. They help in the growth and development of plants. The plants need hormones in lower concentration. Different hormones are classified into different classes depending on their chemical structures.

Complete answer:
-Plant growth regulators are the plant hormones which help in the growth and development of the plants. Plant hormones are also called as the phytohormones. Hormones are not nutrients, they are chemical compounds. These are the signal molecules produced within plants. The plant hormones have different chemical structures but similar physiological effects within the same class. The structure of phytohormones includes carbon, hydrogen, oxygen and nitrogen elements. Plant hormones biosynthesis is not always localized; it is often diffuse within plant tissues.
-Plants produce a wide variety of phytohormones. Among them five major classes of plant hormones are given here: Abscisic acid, auxins, cytokinins, ethylene, and gibberellins. The auxin is responsible for the cell elongation and growth. These are mostly present in the tip of the plant. The leaves of the plants contain the abscisic acid which acts as inhibiting hormone.
-The plant regulators are the simple organic substance of different chemical composition.

Hence, the correct answer is option (A).

Note: Phytohormones play an important role in the growth and development of plants. A single process can be influenced by multiple hormones. Abscisic acid has an adverse effect on growth. It increases seed dormancy by inhibiting cell growth. Phytohormones also break the seed dormancy for many plants and alleviate abiotic stress.