CBSE Questions for Class 11 Medical Biology Plant Growth And Development Quiz 3 - MCQExams.com

• Gibberellic acid stimulates intercalary meristem which promotes elongation of the internode. This is called as bolting effect.
  
• Bolting is when agricultural and horticultural crops prematurely produce a flowering stem before the crop is harvested in a natural attempt to produce seeds. 

Solution:

• Correct answer is option B.
• Explanation for correct option:
•  Gibberellin is a phytohormone which is usually found in acidic nature and hence called as gibberellic acid.
• Gibberellins have role in promoting seed germination.
• Action of mechanism is gibberellins induce production of hydrolysing enzymes.  
• When these hydrolysing enzymes in endosperm are produced, they in turn stimulates the production of digestive enzymes like proteases, amylase and lipase which help to mobilise stored nutrients. Thus inducing the seed germination. 

• Photoperiodism is the ability of plants and animals to measure environmental day length to ascertain the time of year. 
• The GA-induced bolting in rosettes is exploited commercially to induce the early production of seeds. When a cabbage head is kept under warm nights, it retains its rosette habit. 
• Bolting can be induced artificially by the application of gibberellins under normal conditions.

• The cells from the cambium, root apical meristem, and shoot apical meristem differentiate to do various functions. When these differentiated cells regain the capacity to undergo mitotic division the phenomenon is called differentiation.
• Differentiation is the process in which cells of the root system shoot apical meristem and the cambium mature to perform specific functions. 
  
• Cytodifferentiation occurs either spontaneously or under the stimulus of specific nutritional or hormonal factors.
  
• A dedifferentiated plant cell once again loses its capacity to divide and becomes mature. This phenomenon is called redifferentiation.
  
• Thus, the correct answer is option A.

• Cytokinins give the 'Richmond Lang effect', by which the aging (senescence) is delayed in plants. 
• It happened because of the retardation in the destruction of chlorophyll, etc. 
• Thus, it helps in the reduction of leaf fall.

Solution

Correct answer is option B.

Explanation for correct option:

• If a pulse crop shows premature yellowing of leaves and a decrease in yield then the application of magnesium and iron to promote synthesis of chlorophyll may become most beneficial to overcome the problem and to obtain maximum seed yield.
• Magnesium is an important part of ring structure of chlorophyll molecule and its deficiency causes chlorosis and premature leaf abscission.
• In iron deficiency also, the leaves become chlorotic because iron is required for the synthesis of some of the chlorophyll protein complexes in the chloroplast.