CBSE Questions for Class 11 Medical Biology Plant Growth And Development Quiz 4 - MCQExams.com

• Cytokinins delay the senescence of leaves and other organs by controlling protein synthesis and mobilization. 
• This is reported by "Richmond and Lang" in 1957 while working on Xanthium leaves.

Nucleoproteins are any proteins that are structurally associated with nucleic acids, either DNA or RNA. Typical nucleoproteins include ribosomes, nucleosomes. Dedifferentiation refers to the reversion of cells from a highly specialized / differentiated form to less specialized / undifferentiated form or back close to embryonic stage, where the cells divide actively. Since, the main function of nucleoproteins is to participate in regulating DNA replication and transcription that is important for the process of dedifferentiation, nucleoprotein will be highly present during dedifferentiation.

$$\textbf{Correct option: }$$ C

$$\textbf{ Solution: }$$ 

$$\textbf{ Option (a): }$$

$$\bullet$$ Auxins are present at the tip region of the plant stem and promote the growth of the plant. 

$$\bullet$$ The tip of the plant stem is made up of meristematic tissue which is responsible for secretion and storage of auxin hormone.

$$\textbf{ Option (b): }$$

$$\bullet$$ Gibberellin is one of the plant hormones which promotes the growth and differentiation of the plant. 

$$\bullet$$ It also promotes cell differentiation and cell enlargement in the presence of auxin.

$$\bullet$$ Gibberellin are involved in seed germination in certain plants. They break seed dormancy by promoting mobilisation of reserve food material

$$\textbf{ Option (c): }$$

$$\bullet$$ Abscisic acid mainly acts as a plant inhibitor hormone.  It promotes the dormancy of seeds and buds. 

$$\bullet$$ This plant hormone is also responsible for the witting and falling of leaves. 

$$\textbf{ Option (d): }$$

$$\bullet$$ Cytokinins are the plant hormone that promotes the growth of the plant.

$$\bullet$$ Cytokinins promote the ageing of leaves and also help in breaking the dormancy of seeds and buds.

Hence, the correct option is (c).

• Gibberellin (GA) is one of the plant hormones that regulate a wide range of processes involved in plant growth, organ development, and environmental responses.
• Gibberellins are produced in greater mass when the plant is exposed to cold temperatures. They stimulate cell elongation, Growth of stem, breaking and budding, seedless fruits, and seed germination, etc.
  
• Hence the plant hormone responsible for the growth of stem is Gibberellin.
• So, the correct answer is 'Gibberlin'.

• Auxins are generally produced by the growing apices of the stem and roots, from where they migrate to the regions of their action. For example, IAA and indole butyric acid(IBA).
• The primary function of the auxin hormones is to elongate plant cells in the stem. For Example, auxins are the hormones responsible for phototropism, the growth of a plant toward the light.
  
• Hence The plant hormone responsible for elongation of cells. is Auxin.
• So, the correct answer is 'Auxin'.

A) Correct option (D)
B) Explanation of the correct option

• Cytokinin (CK) is a plant hormone.
• It promotes cell division and delays senescence in plants.
• It improves nutrient mobilization and thus delays leaf senescence.
• When applied externally, it mobilizes nutrients towards sites of application.
• It also promotes stomatal opening along with the auxin hormone.
• It also breaks the dormancy of seeds and induces seed germination. 

• Auxins promote stem elongation, inhibit the growth of lateral buds (maintains apical dominance). They are produced in the stem, buds, and root tips. Example: Indole Acetic Acid (IA). Auxin is a plant hormone produced in the stem tip that promotes cell elongation.
  
• Auxins are a powerful growth hormone produced naturally by plants. They are found in shoot and root tips and promote cell division, stem and root growth.
• Auxin and ethylene interaction have shown influence during fruit growth and ripening.
  
• As is the case during embryogenesis, auxin and cytokinin play
  a major role in postembryonic development. Cytokinin reporters are expressed in the procambium, whereas auxin reporters mark the xylem cells

• Auxins promote stem elongation, inhibit growth of lateral buds (maintains apical dominance). They are produced in the stem, buds, and root tips. Example: Indole Acetic Acid (IA).
• The gibberellins are named GA1 through GAn in order of discovery. Gibberellic acid, which was the first gibberellin to be structurally characterized, is GA3.
  
• Zeatin is a cytokinin derived from adenine, which occurs in the form of a cis- and a trans-isomer and conjugates. Zeatin was discovered in immature corn kernels from the genus Zea. It promotes growth of lateral buds and when sprayed on meristems stimulates cell division to produce bushier plants. W
• Abscisic acid (ABA), or Dormin is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure.

• Abscisic acid is a ubiquitous plant hormone which plays an important role in the inhibition of seed germination and budding. It is known as the plant stress hormone and is involved in the response of plants to weather stress, such as tolerance to cold and drought.
• Ethylene promotes senescence and abscission of plant organs especially of leaves and flowers.

• Seedless watermelon plants are grown from seeds. The seeds are produced by crossing a diploid parent with a tetraploid parent to produce triploid seeds. When sprayed on flowers, any of the plant hormones gibberellin, auxin and cytokinin could stimulate the development of parthenocarpic fruit.
• Abscisic acid inhibits germination of mature Arabidopsis seeds by limiting the availability of energy and nutrients. The addition of abscisic acid (ABA) to mature non-dormant seeds inhibits their germination