Free Growth and Development MCQs with Answers

111. Which is employed for artificial ripening of banana fruits?

• A. Auxin
• B. Coumarin
• C. Ethylene
• D. Cytokinin

Explanation: c) : Ethylene is a hormone which is used for ripening of fruit. In case of unripe banana, it can be made to ripe before proper time if they are kept in ethylene atmosphere. Uncontrolled application of this gas may spoil the fruits. Ethylene is produced in mature but unripe fruits and then it initiates a chain of reactions that finally lead to ripening.

112. Abscisic acid causes :

• A. Stomatal closure
• B. Stem elongation
• C. Leaf expansion
• D. Root elongation.

Explanation: a) : Absisic acid is a hormone produced during adverse environmental condition. It also causes the closure of stomata under conditions of water stress as also under high concentration of CO 2 in the guard cells. Abscisic acid inhibits the K+ uptake by guard cells and promotes the leakage of malic acid. It results in reduction of osmotically active solutes so that the guard cells become flaccid and stomata get closed.

113. The hormone responsible for apical dominance is :

• A. IAA
• B. GA
• C. ABA
• D. Florigen

Explanation: a) : In vascular plants especially the taller ones, if the apical bud is intact and growing of the lateral bud remains suppressed, removal of apical bud causes fast growth of lateral buds. This influence of apical bud in suppressing the growth of lateral buds is termed as apical dominance. Indole3acetic acid (IAA) is a natural auxin which is responsible for apical dominance. GA is Giberrellic acid causes rapid elongation growth. ABA (abscisic acid) is a powerful growth inhibitor. Florigen is a chemical involved in flowering.

114. A chemical believed to be involved in flowering is :

• A. Gibberellin
• B. Kinetin
• C. Florigen
• D. IBA

Explanation: c) : Chailakhyan in 1937 gave the view that flower hormone namely florigen is synthesized in the leaves under favourable photoperiodic conditions. This hormone is transmitted to the growing point where the flowering occurs.

115. Twining of tendrils is due to :

• A. Thigmotropism
• B. Seismonasty
• C. Heliotropism
• D. Diageotropism

Explanation: Thigmotropism involves nastic movements resulting from touch. It occurs in tendrils which coil around support and help the plant in climbing. Phototropism is a paratonic movement in response to unidirectional light stimulus. Chemotropism is a directional paratonic movement that occurs in response to a chemical stimulus.

116. Hormone primarily connected with cell division is :

• A. IAA
• B. NAA
• C. Cytokinin/zeatin
• D. Gibberellic acid

Explanation: c) : Cytokinin has a very specific effect on cell division (cytokinesis), hence the name cytokinin. They contain kinetin and related compound generally called as kinins chemically, cytokinins are degradation product of adenine, ATP, NAD and NADP. Cytokinins are essential for cytokinesis though chromosome doubling can occur in their absence. Cytokinins bring about division even in permanent cells.

117. Highest auxin concentration occurs :

• A. In growing tips
• B. In leaves
• C. At base of plant organs
• D. In xylem and phloem

Explanation: a) : Auxins are well known to promote elongation of stem and coleoptile. However when exogenous auxin is given to intact plants this is not observed because the required amount of auxin is already present in plants. When the apex of shoot is removed, then the exogenous application of auxin promotes growth, this clearly indicates that growing apex, having meristematic cells, is the site where endogenous auxins are present in sufficient amount, once the apex is removed the source of auxin is also removed.

118. Phytohormones are :

• A. Chemical regulating flowering
• B. Chemical regulating secondary growth
• C. Hormones regulating growth from seed to adulthood
• D. Regulators synthesised by plants and influencing physiological presses.

Explanation: d) : Growth hormones or phytohormones are defined as organic substances which are synthesized in minute quantities in one part of the plant body and transported to another part where they influence specific physiological processes. Phytohormones are chemical substances which are synthesized by plants and are naturally occurring.

119. Which of the following movement is not related to auxin level ?

• A. Bending of shoot towards light
• B. Movement of root towards soil
• C. Nyctinastic leaf movements
• D. Movement of sunflower head tracking the sun

Explanation: c) : Nyctinastic leaf movement is not related to auxin level. It is a movement of leaves of many species from nearly horizontal leaves during the day and nearly vertical at night. This movement are controlled by biological clock, while the bending of shoot towards light, movement of root towards soil and movement of sunflower head tracking the sun are the conditions related to auxins.

120. Mowing grass lawn facilitates better maintenance because :

• A. Wounding stimulates regeneration
• B. Removal of apical dominance and stimulation of intercalary meristem
• C. Removal of apical dominance
• D. Removal of apical dominance and promotion of lateral meristem

Explanation: b) : Mowing grass lawn facilitates better maintenance because of removal of apical dominance and stimulation of intercalary meristem.