Question

Growth inhibitors are ethylene and abscisic acid.
A. True
B. False

Answer 1

Hint: Plant hormones are chemical substances which have a crucial role in plant’s growth and development. Growth inhibitors are the hormones that inhibit or stop the growth of a plant or any part of a plant mainly root, shoot and bud etc.

Complete Answer:
There are five plant hormones which can act as plant growth regulators (PGR) by initiating the growth of a plant or can act as growth inhibitors by retarding the plant growth. These hormones are auxins, gibberellins, abscisic acid, cytokinins and ethylene. They have their different functions in the plant such as organ formation, cell division dormancy etc.

Let us first focus on the two above given hormones: ethylene and abscisic acid.
- Ethylene promotes fruit ripening which is indirectly facilitated by auxin, geotropism, hastens senescence and inhibits plant growth.
- Abscisic acid on the other hand inhibits the synthesis of enzymes at translation level,imposes dormancy, promotes flowering in short day plants and nullifies the activity of plant growth hormones by promoting enzymes involved in abscission, dormancy.
- Both the hormones ethylene and abscisic acid promote growth inhibition.

Therefore, the correct answer to this question is Option A which is ‘True’.

Note: The other functions of ethylene and abscisic acid are,
1. Ethylene - It helps in fastening of ripening of fruits and also stimulates rapid elongation of internodes and petioles.
2. Abscisic acid - It induces senescence of leaves and inhibits seed germination.