Fasciation (or cresting) is a relatively rare condition of abnormal growth in vascular plants in which the apical meristem (growing tip), that normally is concentrated around a single point and produces approximately cylindrical tissue, instead becomes elongated perpendicularly to the direction of growth, thus producing flattened, ribbon-like, crested, or elaborately contorted tissue. Fasciation can also cause plant parts to increase in weight and volume in some instances. The phenomenon may occur in the stem, root, fruit, or flower head. Some plants are grown and prized aesthetically for their development of fasciation. Any occurrence of fasciation has several possible causes, including hormonal, genetic, bacterial, fungal, viral and environmental.
Fasciation can be caused by hormonal imbalances in the meristematic cells of plants, which are cells where growth can occur. Fasciation can also be caused by random genetic mutation. Bacterial and viral infections can also cause fasciation. The bacterial phytopathogen Rhodococcus fascians has been attributed as a cause of fasciation, but many fasciated plants have tested negative for the bacteria in studies, hence bacterial infection is not an exclusive causation. It has been demonstrated that the bacteria Rhodococcus fascians causes fasciation to occur in pea (Pisum sativum) plants.
Additional environmental factors that can cause fasciation include fungi, mite or insect attack and exposure to chemicals. General damage to a plant's growing tip and exposure to cold and frost can also cause fasciation. Some plants, such as peas and cockscomb Celosia, may inherit the trait.
Fasciation is not contagious, but bacteria that cause fasciation can be spread from infected plants to others from contact with wounds on infected plants and from water that carries the bacteria to other plants.
Although fasciation is rare overall, it has been observed in over 100 plant species, including members of the genera Acer, Aloe, Cannabis, Celosia, Delphinium, Digitalis, Euphorbia, Forsythia, Glycine max (specifically, soybean plants), Primula, Prunus, Salix and many genera of the Cactaceae (cactus) family. Cresting results in undulating folds instead of the typical "arms" found on mature Saguaro cactus.
Some varieties of Celosia are raised especially for their dependably fasciated flower heads, for which they are called "cockscomb". The Japanese Fantail Willow (Salix sachalinensis 'Sekka') is another plant that is valued for its fasciations.
Fasciation caused by bacteria can be controlled by not using and disposing fasciated plants. Avoiding injury to plant bases and keeping them dry can reduce the spread of bacteria. Avoidance of grafting fasciated plants and the pruning of fasciated matter can also reduce the spread of bacteria.
See also 
- White, Orland E. (June 1948). "Fasciation (Preview, page 319)". Volume 14, No. 6. The Botanical Review. pp. 319–358. Retrieved July 07, 2012. DOI: 10.1007/BF02861723 (subscription required)
- Albertsen, Marc E.; et al. (June 1983). "Genetics and Comparative Growth Morphology of Fasciation in Soybeans (Glycine max (L.) Merr.) (Preview, page 263)". Volume 144, No. 2. Botanical Gazette. pp. 263–275. Retrieved July 07, 2012. (subscription required)
- Lerner, B. Rosie (September 2007). "Fascinating Fasciation". Purdue University Extension. Retrieved July 03, 2012.
- Galun, Esra (2007). Plant Patterning: Structural and Molecular Genetic Aspects. World Scientific Publishing Company. p. 333. ISBN 9789812704085
- "Fasciation in Vegetables and Fruits". University of Delaware Cooperative Extension. May 27, 2011. Retrieved July 06, 2012.
- Swift, Curtis E. (April 12, 1999). "Fasciation: Fascinating distortions of the plant world". Colorado State University Extension. Retrieved July 03, 2012.
- Tilford, P.E. (1936). "Fasciation of Sweet Peas caused by Phytomonas fascians n.sp.". Volume 53, No. 5. Journal of Agricultural Research. pp. 383–394. Retrieved July 07, 2012. (subscription required)
- "Pests in Gardens and Landscapes". Statewide Integreated Pest Management Program, Agriculture and Natural Resources, University of California. October 13, 2008. Retrieved July 03, 2012.
- Yamamoto, Etsuo; et al. (April 25, 2000). "Molecular characterization of two soybean homologs of Arabidopsis thaliana CLAVATA1 from the wild type and fasciation mutant (Abstract)". Volume 1491, Issues 1-3. Gene Structure and Expression. pp. 333–340. Retrieved July 07, 2012. (subscription required)
- "Campus Arboretum". University of Arizona. 2008-08-20. Retrieved 2010-01-14.
Further reading 
- White, Orland E. (1945). "The Biology of Fasciation (Preview, page 11)". Volume 36, Issue 1. Journal of Heredity. pp. 11–22. Retrieved July 07, 2012. (subscription required)
- Crespi, M.; et al. (March 1992). "Fasciation induction by the phytopathogen Rhodococcus fascians depends upon a linear plasmid encoding a cytokinin synthase gene". Volume 11, No. 3. The EMBO Journal. pp. 795–804. Retrieved July 07, 2012.
- Nilsson, O.; et al. (October 1996). "Expression of the Agrobacterium rhizogenes rolC Gene in a Deciduous Forest Tree Alters Growth and Development and Leads to Stem Fasciation". Volume 112, No. 2. Plant Physiology. pp. 493–502. Retrieved July 07, 2012.
- Crespi, M.; et al. (May 1994). "The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants (Abstract)". Volume 176, No. 9. Journal of Bacteria. pp. 2492–2501. Retrieved July 07, 2012. (subscription required)
|Central Texas Gardener: Fasciated Mountain Laurel. KLRU-TV, Austin PBS.|
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- Ombrello, T. (PhD). "Fascinating Fasciated Plants". Union County College, Cranford, NJ. Retrieved July 06, 2012.
- "Definition of "Fasciation"". Merriam-Webster Dictionary. Retrieved July 06, 2012.