Analyze the specific functions of Auxins vs Cytokinins in tissue culture callus differentiation:
(i) Auxin alone added to tissue culture medium induces root differentiation. (ii) Cytokinin plus auxin in appropriate ratio induces callus proliferation and shoot formation. (iii) High cytokinin to auxin ratio favors shoot differentiation. (iv) Omission of cytokinin from nutrient medium prevents cell division in callus.
All four statements (i), (ii), (iii), and (iv) are correct statements regarding auxin-cytokinin interactions in plant tissue culture.
Question 82 of 100
📘 CLASS XI
Examine the role of Gibberellins in seed germination and enzyme induction:
(i) GAs break seed dormancy in cereal grains. (ii) GAs induce synthesis of hydrolytic enzymes like alpha-amylase in aleurone layer during cereal germination. (iii) Hydrolytic enzymes break down stored starch into sugars for embryonic growth. (iv) ABA acts synergistically with GA to increase alpha-amylase synthesis.
Statements (i), (ii), and (iii) are correct regarding GA induction of alpha-amylase during cereal seed germination. Statement (iv) is incorrect because ABA inhibits GA action and inhibits seed germination.
Question 83 of 100
📘 CLASS XI
Consider the effect of ethylene on flowering and sex expression in crop plants:
(i) Ethylene initiates flowering in pineapples. (ii) Ethylene synchronizes fruit-set in pineapples. (iii) Ethylene induces flowering in mango. (iv) Ethephon promotes male flowers in cucumbers to decrease fruit set.
Statements (i), (ii), and (iii) are correct regarding pineapple flowering/fruit-set and mango flowering. Statement (iv) is incorrect because ethephon promotes female flowers in cucumber, increasing yield.
Question 84 of 100
📘 CLASS XI
Evaluate the physiological action of ABA during water stress / drought conditions:
(i) ABA concentrations increase rapidly in leaves during water stress. (ii) ABA stimulates stomatal closure to prevent transpirational water loss. (iii) ABA increases tolerance of plants to various environmental stresses. (iv) ABA opens stomata wide to increase transpiration and cool leaf surface during drought.
Statements (i), (ii), and (iii) are correct regarding ABA accumulation, stomatal closure, and stress tolerance. Statement (iv) is incorrect because ABA closes stomata.
Question 85 of 100
📘 CLASS XI
Examine the historical discoveries of plant growth regulators and their key researchers:
(i) Auxin phototropism experiments: Charles Darwin and Francis Darwin. (ii) Isolation of auxin from oat coleoptiles: F.W. Went. (iii) Bakanae disease / Gibberellin discovery: E. Kurosawa. (iv) Ethylene discovery from ripened oranges: H.H. Cousins.
All four pairings (i: Darwins/phototropism, ii: Went/auxin isolation, iii: Kurosawa/gibberellin, iv: Cousins/ethylene) are completely correct based on textbook historical accounts.
Question 86 of 100
📘 CLASS XI
Regarding the discovery of cytokinins by Skoog and Miller, evaluate these statements:
(i) F. Skoog and co-workers used tobacco stem internodal segments in tissue culture. (ii) Proliferation of callus required auxin plus vascular extract, yeast extract, coconut milk, or DNA. (iii) Miller et al. (1955) crystallized kinetin from autoclaved herring sperm DNA. (iv) Skoog and Miller isolated kinetin from fresh living tobacco leaves.
Statements (i), (ii), and (iii) are correct regarding Skoog's tobacco stem callus experiments and Miller's isolation of kinetin from herring sperm DNA. Statement (iv) is incorrect because kinetin was isolated from autoclaved herring sperm DNA.
Question 87 of 100
📘 CLASS XI
Which of the following compounds are recognized as synthetic auxins?
Statements (iii) and (iv) are synthetic auxins (NAA and 2,4-D), whereas statements (i) and (ii) are natural auxins (IAA and IBA) isolated from plants.
Question 88 of 100
📘 CLASS XI
Consider the effect of Auxins on flowering and fruit drop in pineapple and other crops:
(i) Auxins promote flowering in pineapples. (ii) Auxins prevent premature fruit and leaf drop. (iii) Auxins promote abscission of older mature leaves and fruits. (iv) Auxins prevent flowering in all monocotyledonous crops.
Statements (i), (ii), and (iii) are correct regarding auxin-induced pineapple flowering and organ drop prevention/promotion. Statement (iv) is incorrect.
Question 89 of 100
📘 CLASS XI
Examine the role of Gibberellins in bolting and stem elongation:
(i) Bolting is the internode elongation just prior to flowering. (ii) Gibberellins promote bolting in beet and cabbages. (iii) Plants with rosette habit undergo bolting upon treatment with gibberellins. (iv) Abscisic acid (ABA) promotes bolting in cabbage and beet.
Statements (i), (ii), and (iii) are correct definitions and examples of bolting promoted by gibberellins. Statement (iv) is incorrect because gibberellins, not ABA, promote bolting.
Question 90 of 100
📘 CLASS XI
Regarding the effects of Cytokinins on chloroplast development and leaf growth, analyze:
(i) Cytokinins promote production of new leaves. (ii) Cytokinins promote development of chloroplasts in leaves. (iii) Cytokinins promote lateral shoot growth and adventitious shoot formation. (iv) Cytokinins destroy chloroplast pigments and cause leaf yellowing.
Statements (i), (ii), and (iii) are correct regarding cytokinin roles in new leaves, chloroplast production, lateral shoot growth, and adventitious shoot formation. Statement (iv) is incorrect because cytokinins promote chloroplast development and delay leaf senescence.
