Examine the general characteristics and diversity of gibberellins:
(i) More than 100 gibberellins have been reported from fungi and higher plants. (ii) They are denoted as GA1, GA2, GA3, etc. (iii) Gibberellic acid (GA3) was one of the first discovered and most intensively studied gibberellins. (iv) All gibberellins are chemically basic or alkaline compounds.
Statements (i), (ii), and (iii) are correct regarding GA diversity and GA3 discovery. Statement (iv) is incorrect because all gibberellins are acidic.
Question 32 of 100
📘 CLASS XI
Which of the following physiological effects are produced by gibberellins?
(i) Cause increase in length of axis, used to increase length of grapes stalks. (ii) Cause fruits like apple to elongate and improve its shape. (iii) Delay senescence, allowing fruits to be left on the tree longer to extend market period. (iv) Hasten abscission and senescence in ripening fruits.
Statements (i), (ii), and (iii) are correct because gibberellins elongate axes and grape stalks, elongate apples, and delay senescence. Statement (iv) is incorrect because gibberellins delay senescence.
Question 33 of 100
📘 CLASS XI
Analyze the commercial and agricultural applications of Gibberellic acid (GA3):
(i) GA3 is used to speed up the malting process in the brewing industry. (ii) Spraying sugarcane crop with gibberellins increases stem length, increasing yield by up to 20 tonnes per acre. (iii) Spraying juvenile conifers with GAs hastens maturity period, leading to early seed production. (iv) GAs promote bolting (internode elongation prior to flowering) in beet, cabbages, and rosette plants.
All four statements (i), (ii), (iii), and (iv) are correct regarding brewing malting, sugarcane yield, conifer seed production, and bolting in rosette plants.
Question 34 of 100
📘 CLASS XI
Regarding the discovery and nature of cytokinins, evaluate these statements:
(i) Cytokinins have specific effects on cytokinesis. (ii) Kinetin is a modified form of adenine (a purine) discovered from autoclaved herring sperm DNA. (iii) Zeatin is a naturally occurring cytokinin isolated from corn kernels and coconut milk. (iv) Kinetin occurs naturally in high concentrations in coconut milk and young maize grains.
Statements (i), (ii), and (iii) are correct regarding cytokinesis, kinetin, and zeatin. Statement (iv) is incorrect because kinetin does not occur naturally in plants.
Question 35 of 100
📘 CLASS XI
Identify the regions of synthesis and physiological effects of natural cytokinins:
(i) Natural cytokinins are synthesized in regions of rapid cell division (root apices, developing shoot buds, young fruits). (ii) Cytokinins help produce new leaves, chloroplasts in leaves, lateral shoot growth, and adventitious shoot formation. (iii) Cytokinins help overcome apical dominance. (iv) Cytokinins promote nutrient mobilization which helps in delaying leaf senescence.
All four statements (i), (ii), (iii), and (iv) accurately summarize cytokinin synthesis sites and physiological effects.
Question 36 of 100
📘 CLASS XI
Consider the biosynthesis and general physiological roles of ethylene:
(i) Ethylene is a simple gaseous plant growth regulator. (ii) It is synthesized in large amounts by tissues undergoing senescence and ripening fruits. (iii) Influences on dicot seedlings include horizontal growth, swelling of the axis, and apical hook formation. (iv) Ethylene prevents senescence and abscission of plant organs like leaves and flowers.
Statements (i), (ii), and (iii) are correct regarding gaseous ethylene, synthesis in senescing and ripening tissues, and the triple response. Statement (iv) is incorrect because ethylene promotes senescence and abscission.
Question 37 of 100
📘 CLASS XI
Evaluate the role of ethylene in fruit ripening and plant respiration:
(i) Ethylene is highly effective in fruit ripening. (ii) It enhances the respiration rate during ripening of fruits. (iii) The rise in rate of respiration during fruit ripening is called respiratory climactic. (iv) Ethylene suppresses cellular respiration to prolong fruit storage life.
Statements (i), (ii), and (iii) are correct regarding fruit ripening and respiratory climactic. Statement (iv) is incorrect because ethylene enhances respiration during ripening.
Question 38 of 100
📘 CLASS XI
Examine the effects of ethylene on seed/bud dormancy and aquatic adaptation:
(i) Ethylene breaks seed and bud dormancy. (ii) Ethylene initiates germination in peanut seeds and sprouting of potato tubers. (iii) Ethylene promotes rapid internode/petiole elongation in deep water rice plants. (iv) Rapid petiole elongation in deep water rice helps leaves and upper shoot parts to remain above water.
All four statements (i), (ii), (iii), and (iv) are true regarding dormancy breaking in peanuts/potatoes and petiole/internode elongation in deep water rice.
Question 39 of 100
📘 CLASS XI
Analyze the effects of ethylene on root growth and agricultural flowering applications:
(i) Ethylene promotes root growth and root hair formation, increasing absorption surface. (ii) Ethylene is used to initiate flowering and synchronize fruit-set in pineapples. (iii) Ethylene induces flowering in mango. (iv) Ethylene completely inhibits root hair development in all angiosperms.
Statements (i), (ii), and (iii) are correct regarding root hair formation, pineapple flowering/fruit-set, and mango flowering. Statement (iv) is incorrect because ethylene promotes root hair formation.
Question 40 of 100
📘 CLASS XI
Regarding ethephon and its agricultural applications, evaluate the following statements:
(i) Ethephon is the most widely used compound as a source of ethylene in agriculture. (ii) Ethephon in aqueous solution is readily absorbed and transported within the plant, releasing ethylene slowly. (iii) Ethephon hastens fruit ripening in tomatoes and apples. (iv) Ethephon accelerates thinning (abscission) in cotton, cherry, and walnut, and promotes female flowers in cucumbers.
All four statements (i), (ii), (iii), and (iv) accurately describe ethephon composition, slow ethylene release, tomato/apple ripening, thinning in cotton/cherry/walnut, and female flowering in cucumbers.
