Growth and Development in Plants MCQs for NEET — Botany Questions with Answers

Page number-198

12.2.2 Role of Macro and Micronutrients

Mineral Nutrition

(b) Parthenocarpy is the phenomenon of development of seedless fruits (without pollination and fertilization). Parthenocarpy can be induced by auxins as well as gibberellins but the latter are more potent parthenocarpic agents.

(b) : Vernalization is a process of shortening of the juvenile or vegetative phase and hastening flowering by a previous cold treatment. The term vernalization was coined by Lysenko (1928).

The bud dormancy is induced by abscisic acid (ABA). The level of endogenous ABA increases with the onset of dormant period and decreases when it is broken.

Answer is (d)

Growth regulators are organic substances, other than nutrients, which in low concentration regulate growth, differentiation and development by promoting or inhibiting the same. Phytohormones are growth regulators produced naturally in plants and translocated to another region for regulating one or more physiological reactions when present in low concentration. Phytohormone can have at promoting or inhibiting effect on a process.

(d) Abscisic acid acts as a general plant growth inhibitor and an inhibitor of plant metabolism.
ABA inhibits seed germination. ABA stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone.

(b) Auxins promote root initiation at a concentration which otherwise is inhibitory for growth of intact root. Auxins are often employed for inducing flowering in litchi and pineapple. Application of auxins to unpollinated pistils make them develop into seedless fruits or parthenocarps.

(c) Vernalisation refers specially to the promotion of flowering by exposure to a period of low temperature. Many temperate plants have vernalisation requirement and must experience a period of low temperature in winter, to initiate or accelerate flowering process, or in many fruit tree species, to induce dormancy and then break dormancy prior to flowering.