Fasciation
 Central Texas Gardener: Fasciated Mountain Laurel. KLRU-TV, Austin PBS. |
Fasciation (pronounced /ˌfæʃiˈeɪʃən/, from the Latin root meaning "band" or "stripe"), also known as cresting, is a relatively rare condition of abnormal growth in vascular plants in which the apical meristem (growing tip), which 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 "cristate"), or elaborately contorted tissue. Fasciation may 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 causes.
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 demonstrated as one cause of fasciation, such as in sweet pea (Lathyrus odoratus) plants, but many fasciated plants have tested negative for the bacteria in studies, hence bacterial infection is not an exclusive causation.
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