Role of Major Hormone Presentation

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Cytokinin Growth Hormone

Presented by: Lashon Blakely, Antwan Nails, and Brittany ValdezBIO/204

Content

Introduction – Overview of CytokininHistory of scientific inquiry An experiment that led to better understandingDevelopment of structuresCytokinin influences on plant growthEffects of hormone deficiency and excessReview of hormone Conclusion

Introduction

Plant hormones function to protect plant development and to stabilize plant growth. The classic five hormones are auxin, ethylene, cytokinin, abscisic acid (ABA), and gibberellins.

Cytokinin and Functions

Cytokinin plant hormone is part of bud activation and promotes cell division. Cytokinins were named by the way that their addition to a tissue culture medium containing auxin and sugar stimulates cell division. In the spring, large amounts of cytokinins are transported to the shoot causing buds to expand and activate.

History of scientific inquiry

Discovered during the 1950s by Carlos Miller. It regulates cell division, and to stimulate shoot and root growth. Hypothesis predicted that cytokinin, together with auxin plays a main role.Cytokinin-deficent plants developed stunted shoots with smaller apical meristems.

Experiment that led to better understanding

Skoog and Miller experiment through tobacco plants show cytokinins are essential for growth.The purpose for the experiment was to get a better understanding of cytokinins.Root meristems of transgenic plants were enlarged and rise to faster growing.

Plant structures and functions are associated with Cytokinin

A typical plant body; a root system and a shoot systemThree types of meristems in plants; namely apical, intercalary and lateral meristems The lateral meristems are known as cambiumsMost of the cytokinins required for the plant body are synthesized in the root tipsCan also occur in root cap cells, ovules, phloem cells, leaf axills, fruit and seeds

Plant structures and functions are associated with Cytokinin

Involved in cell division by activating the cyclin-dependent protein kinases (cdks) and cyclinesHelp in promoting mitosis (werner, etal. 2001).Slow down the aging process of the plants by preventing protein breakdownDelays the leaf senescence Preventing the degradation of chloroplasts Many produce farmers use it for increasing the crop yield (QH ma. 2008).

Taiz, L. and Zeiger, E. (2010)

Used to treat dormant buds In inducing division in inflorescence tips which can lead to more fruitsRole in cell enlargement which helps in increasing the respiratory activityPlay a role in inducing resistanceLinked to controlling infections and other plant diseases

Plant structures and functions are associated with Cytokinin

Effects of hormone deficiency and excess on plant growth or function

Overabundant in the root, the cell division is inhibited (figure A) but if there is overabundance in the shoot, the cell division is promoted (figure D)Cytokinin oxidase dictates meristemic cytokinin concentrationsReference for the figures:Lu C & Fedoroff, N. 2000

Conclusion-Main points of cytokinin highlighted

Involved in DNA expressionRespond to plant needs and works with other hormonesPrevents protein breakdown, thereby slowing down the aging process.Excess or deficiency can cause damage to plants at various levels.

References

Cytokinin. (2015). In The Hutchinson unabridged encyclopedia with atlas and weather guide. Abington, United Kingdom: Helicon. Retrieved from http://search.credoreference.com/content/entry/heliconhe/cytokinin/0Mauseth, J.(2014). Botany: An introduction to plant biology (5th ed.). Burlington, MA: Jones & Bartlett Leahttp://labs.bio.unc.edu/Kieber/cytokinin%20historhttp://labs.bio.unc.edu/Kieber/cytokinin%20history.htmSantner, A., Calderon-villalobos, L., & Estelle, M. (2009). Plant hormones are versatile chemical regulators of plant growth. Nature Chemical Biology, 5(5), pp. 305-306. doi:http://dx.doi.org/10.1038/nchembio.165 Secondary Growth Structure. Retrieved from: http://bio1152.nicerweb.com/Locked/media/ch35/growth-secondary.htmlThe Structure and Function of Flowers. Retrieved from: leavingbio.netLu C & Fedoroff, N. 2000. A mutation in the Arabidopsis HYL1 gene encoding a dsRNA binding protein affects responses to abscisic acid, auxin, and cytokinin. Plant Cell. 2000 Dec;12(12):2351-2366. doi:10.1105/tpc.12.12.2351Taiz, L. and Zeiger, E. (2010) Plant Physiology. 5th Edition, Sinauer Associates, Inc., Sunderland.Werner, etal. 2001. Regulation of plant growth by cytokinin. retrieved from http://www.pnas.org/content/98/18/10487.full.pdf on March 27th, 2016.




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