47. Which one of the following combinations of cytokinins (CKs) represent only Isoprenoid CKs?
1. Trans-Zeatin and Benzyladenine
2. Ortho-Topolin and meta-Topolin
3. Cis-Zeatin and Dihydrozeatin
4. Trans-Zeatin and Benzyladenine

Understanding Isoprenoid Cytokinins: Key Roles and Types

Cytokinins (CKs) are essential plant hormones that regulate cell division, differentiation, and senescence. They are broadly classified into two types: isoprenoid cytokinins and aromatic cytokinins.

Classification of Cytokinins

1. Isoprenoid Cytokinins
   • Derived from isoprenoid precursors.
   • Found naturally in plants.
   • Examples: Trans-Zeatin, Cis-Zeatin, Dihydrozeatin, Isopentenyladenine (iP).
2. Aromatic Cytokinins
   • Derived from aromatic rings.
   • Less common in nature.
   • Examples: Benzyladenine (BA), Ortho-Topolin, Meta-Topolin.

Correct Answer: 3. Cis-Zeatin and Dihydrozeatin

These two cytokinins belong to the isoprenoid category and play a crucial role in plant growth and development.

Functions of Isoprenoid Cytokinins

• Promote cell division and shoot initiation.
• Delay leaf senescence (anti-aging effects in plants).
• Regulate seed germination and root growth.
• Influence nutrient mobilization and stress responses.

Explanation of Answer Choices

Comparison Between Isoprenoid and Aromatic Cytokinins

Conclusion

Cytokinins play a critical role in plant development, and Cis-Zeatin and Dihydrozeatin are confirmed as isoprenoid cytokinins. Understanding their classification helps in plant biotechnology and agricultural advancements.

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