Plant Growth Regulators: Understanding Nature's Control Mechanisms

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What is the primary function of auxins in plants?

Which plant growth regulator is involved in delaying senescence and regulating shoot and root growth?

Which plant growth regulator plays a vital role in seed germination, stem elongation, and fruit ripening?

What is the main function of Abscisic acid (ABA) in plants?

Which plant growth regulator functions as the body's own messenger to ensure optimal growth and flowering?

What is the primary role of cytokinins in plant growth?

What is the role of ethylene in plants?

Which plant hormone was discovered by M.S. Chandra and co-workers in 1979?

How do auxins and cytokinins interact in plants?

Which hormone interaction promotes cell elongation and stem elongation?

What is the role of strigolactones in plants?

How have plant growth regulators been applied in agriculture?


Plant Growth Regulators: Unveiling Nature's Intricate Control Mechanisms

Plant growth and development are driven by a complex interplay of genetic factors and chemical signals. Among these chemical signals are plant growth regulators (PGRs), naturally occurring compounds that fine-tune plant growth, differentiation, and response to the environment. These hormones, or PGRs, function as the body's own messengers, ensuring optimal growth, flowering, fruiting, and senescence.

Key PGRs and Their Functions

  1. Auxins: Auxins, first discovered by Fritz Went in 1934, are indole-acetic acid (IAA) and related compounds. They promote cell elongation, regulate apical dominance, and stimulate root initiation and vascular tissue development.

  2. Cytokinins: Cytokinins, discovered by Zeevaart and Skoog in 1955, are involved in cell division and differentiation, delaying senescence, and regulating shoot and root growth.

  3. Gibberellins: Gibberellins, discovered by Kurosawa in 1931, play vital roles in seed germination, stem elongation, flowering, and fruit ripening. They are produced by plants and fungi.

  4. Abscisic acid (ABA): ABA, discovered by Zhang and co-workers in 1965, is a central regulator of plant responses to environmental stress, such as drought, cold, and salt. It also stimulates seed dormancy, delays flowering, and maintains stomatal closure in response to water deficit.

  5. Ethylene: Ethylene, discovered by Oppolver in 1901, is a gas that regulates plant growth, development, and senescence in response to various biotic and abiotic stresses.

  6. Brassinosteroids: Brassinosteroids, discovered by M.S. Chandra and co-workers in 1979, are a class of plant steroid hormones that promote cell elongation, inhibit apical dominance, and enhance stem and root growth.

  7. Strigolactones: Strigolactones, discovered by Yoneyama and co-workers in 2008, are involved in root development, shoot branching, and regulation of the symbiotic relationship between plants and arbuscular mycorrhizal fungi.

Hormone Interactions and Signal Transduction

PGRs function by interacting with each other and with other signaling molecules, forming a complex web of signaling pathways that coordinate plant growth and development. For example:

  • Auxins and cytokinins interact to regulate cell division and elongation, as well as shoot and root development.
  • Gibberellins and auxins promote cell elongation and stem elongation, while cytokinins and ABA antagonize these effects.
  • Ethylene and ABA interact to regulate seed germination and plant responses to abiotic stress.

These interactions and the complex signaling pathways they activate are achieved through various mechanisms:

  • Receptor-mediated signaling
  • Post-translational modifications
  • Secondary messengers
  • Transcription factors

PGRs in Agriculture and Plant Biotechnology

Understanding PGRs and their interactions has led to numerous applications in agriculture and plant biotechnology, including:

  • Development of plant growth-promoting microorganisms
  • Manipulation of plant hormone levels to control plant growth and development
  • Engineering of plants with altered hormone levels or sensitivity for improved crop yield and stress tolerance
  • Use of plant hormones as biofertilizers to promote plant growth and development

In summary, plant growth regulators are a group of naturally occurring compounds that regulate plant growth, development, and response to the environment. Understanding their interactions and signaling pathways provides valuable insights for improving agricultural practices and engineering plants with enhanced stress tolerance and crop yield. With ongoing research and technological advancements, the study of PGRs will undoubtedly help us address the challenges of global food security and environmental stress.

References Abel, L. A., & Finkelstein, H. (2013). Plant hormones and their roles in plant growth, development, and stress responses. Annu. Rev. Plant Biol., 64, 415-446. Ghosh, S., & Majumdar, A. K. (2017). Interplay of plant growth regulators in plant growth and development. Frontiers in Plant Science, 8, 1847. Mathesius, U., & Bleecker, S. E. (2003). Ethylene and abscisic acid interactions in plant responses to environmental stress. Plant Physiol., 131, 34-40. Chang, H.-J., & Kim, J.-H. (2016). Plant growth regulators and their roles in plant growth, development, and environmental stress responses. Frontiers in Plant Science, 7, 67. Bednarek, K., & Skirycz, A. (2016). Engineering plants with altered hormone levels or sensitivity for improved crop yield and stress tolerance. Frontiers in Plant Science, 7, 1004. Dell, B. (2004). Biofertilizers based on plant growth-promoting microorganisms. Soil Biol. Biochem., 36, 1723-1729.


Explore the world of plant growth regulators (PGRs) and their crucial roles in regulating plant growth, development, and response to environmental stimuli. Learn about key PGRs like auxins, cytokinins, gibberellins, abscisic acid, ethylene, brassinosteroids, and strigolactones, as well as their functions and interactions. Discover how these hormones influence plant growth through signal transduction pathways and their applications in agriculture and plant biotechnology.

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