Free Growth and Development MCQs with Answers

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

• A. Auxin
• B. Cytokinin
• C. Ethylene
• D. Abscisic Acid

Explanation: a) : Zinc is available to the plants for absorption in the divalent form. It occurs in the form of minerals as hornblende, magnetite, biotite etc., from where it is released by weathering. It is involved in the synthesis of Indoleacetic acid in plants. It is an activator in the enzyme tryptophan synthetase. Tryptophan is the precursor of Indoleacetic acid.

82. Which of the following prevents the fall of fruits?

• A. GA3
• B. NAA
• C. Ethylene
• D. Zeatin

Explanation: b) : Naphthalene acetic acid (NAA) is a synthetic or exogenous auxin. It prevent the formation of abscission layer, which is a layer of dead cells in the petiole and pedicel that causes fall of leaf or fruit. NAA prevents formation of this layer and so it prevents fall of leaf or fruit.

83. Hormone responsible for senescence is :

• A. ABA
• B. Auxin
• C. GA
• D. Cytokinin

Explanation: (a) : Abscisic acid is a growth inhibiting phytohormone. It induces senescence in leaves by promoting the degradation of chlorophyll and proteins. Auxin is a growth promoting phytohomone that results in cell division, cell enlargement and apical dominance. Cytokinin is a growth promoting phytohormone that causes cell division, morphogenesis and seedling growth. Gibberellins are growth promoting phytohormone that results in overcoming seed dormancy and bolting.

84. Which hormone breaks dormancy of potato tuber?

• A. Gibberellin
• B. IAA
• C. ABA
• D. Zeatin

Explanation: (a): Gibberellin is the hormone that breaks seed/ bud dormancy. The tubers of potato reproduce vegetatively to give rise to new plants. So the dormancy of these tubers can be overcome by applying gibberellins.

85. If the apical bud has been removed then we observe :

• A. More Lateral Branches
• B. More Axillary Buds
• C. Plant Growth Stops
• D. Flowering Stops

Explanation: (a) : Apical dominance is the phenomenon by which presence of apical bud does not allow the nearby lateral buds to grow. When apical bud is removed, the lateral buds sprout.

86. By which action a seed coat becomes permeable to water :

• A. Scarification
• B. Stratification
• C. Vernalization
• D. all of the above.

Explanation: (a) : Scarification means the application of those methods by which the hard seed coat is ruptured or softened so that it becomes permeable to water, gases and the embryo can expand. There are two methods of scarification as mechanical scarification and chemical scarification. This helps in overcoming seed dormancy.

87. Which hormone is responsible for fruit ripening?

• A. Ethylene
• B. Auxin
• C. Ethyl chloride
• D. Cytokinin

Explanation: (a) : Ethylene is largely a growth inhibiting phytohormone but is also involved in some growth promotion activities. It has been established that Chapterwise NEETAIPMT SOLUTIONS ethylene is a fruit ripening hormone. Ethylene stimulates all the biochemical changes which take place at the time of fruit ripening.

88. ABA is involved in :

• A. Shoot Elongation
• B. Increased Cell Division
• C. Dormancy of Seeds
• D. Root Elongation.

Explanation: (c) : Abscisic acid (ABA) is a growth inhibiting phytohormone. Abscisic acid is found in vascular plants, some mosses, some fungi and some green algae. If ABA is applied exogenously, seed germination is inhibited. It has been suggested that ABA inhibits the synthesis of some enzymes, for germination. These enzymes are synthesised under the direction of nucleic acids. A view has been expressed that the translation of a particular messenger RNA is inhibited by ABA and the result is that protein synthesis is blocked.

89. The closing and opening of the leaves of Mimosa pudica is due to :

• A. Seismonastic Movement
• B. Chemonastic Movement
• C. Thermonastic Movement
• D. Hydrotropic Movement.

Explanation: (a) : Nastic movements occur in response to a stimulus. It is independent of its direction. They are shown by bifacial organs (leaves, sepals, petals) and are in response to diffused external stimulus.Seismonastic movements are due to shock or touch stimulus. Such movements are shown by Mimosa pudica. The leaf ofMimosa is compound having four pinna and each pinna is having many pinnules. If a terminal pinnule is touched, the whole leaf droops down. This is due to fact that at the bases of pinnules, pinna and whole leaf, swollen structure called pulvinus is present and drooping is due to loss of turgidity of lower portion of pulvinus.

90. A plant hormone used for inducing morphogenesis in plant tissue culture is :

• A. Cytokinins
• B. Ethylene
• C. Abscisic Acid
• D. Gibberellins

Explanation: (a) : Cytokinins are growth promoting phyto homones. Cytokinin plays an important part in organ formation (morphogenesis) with auxin. Different auxin/cytokinin ratio decides the development of root shoot ratio. The major physiological function of cytokinins is to enhance cell division. If cytokinin to auxin ratio is low, then root formation takes place but if the ratio of cytokinin to auxin is high, then, there is formation of meristematic cells in the callus.