Fasciation in plants is a bizarre mutation in the meristem (growing point) leading to flattened flower stems and distorted flowers, fruits and roots. It can also lead to a ring of small flowers surrounding the main flower, this is known as ‘hen and chicks’ and can be seen in some of the Veronicastrum pictures below. The meristem is where cells actively divide in order to grow or create new flowers and leaves, a disturbance to this process can lead to the cell division intensifying and occurring in a haphazard manner, leading to distortion. Essentially the growing point ceases to be a point and instead forms a cockscomb. For many plants this is most commonly noticed with flowers, which then go on to form distorted fruits, but with cacti and ferns it is often seen in the leaves.
In some plants, such as the soybean (Glycine max), fasciation is caused by a single recessive gene. This means that fasciation will only occur if both parents of a plant have that gene and pass it on.
In plants without the gene, fasciation is caused by disturbance to the meristem at the time of growth. This disturbance can be caused by
- Mites or insects feeding on the shoot
- Fungal, bacterial and viral diseases
- A sudden change in temperature – eg going from low to high or high to low (especially in Hyacinthus)
- Zinc deficiency or nitrogen excess
- Drought followed by heavy watering
Frequently Fasciated Plants
The following plants have exhibited fasciation: soybean, many cacti, ferns, Euphorbia, Prunus, Salix, cannabis, Aloe, Acer, Forsythia, Delphinium, Digitalis, Taraxicum and Syringa.
Artificially Induced Fasciation
In some cases fasciation is seen as a desirable characteristic, it can lead to increased yield in crops due to the enlarged heads, or provide a talking point in ornamental displays. Examples are the maize, Celosia cristata and Asplenium cristata (note the species name ‘cristata’ – cristate is another word for fasciation). To this end, the above conditions can be induced or one of the following methods used:
- Manipulating the photoperiod (exposure to light)
- Using susceptible cultivars (see below)
- Using radiation – gamma rays or ionizing x-rays.
- Chemical application – growth regulators or polyploidzing agents
- A cutting or scion taken from a fasciated plant will create a new fasciated plant
Veronicastrum ‘Fascination’ is a cultivar grown for its tendency to fasciate.
Fasciation in Cacti and Other Succulents
Many cacti and succulents are subject to fasciation, although the word more commonly used to describe this state is cristate. More than fifty cacti genera have shown cristation, as well as the succulent families Crassulaceae, Asclepiadaceae and Euphorbiaceae. Some cacti have ‘Cristata’ in the name. Fasciated cacti form ribbon like weaves, or have many divisions. Cristation is often cultivated in cacti, with cuttings used to perpetuate the cristate cacti. It is thought that some cacti species have a genetic propensity to cristation and somatic mutation (genetic alteration caused by environmental factors as described above) leads to the physical changes. Seeds from fasciated stems in cacti often lead to fasciated seedlings, although this is not necessarily true of other plants, Digitalis, when fasciated, does not produce fasciated seedlings.
Some more cacti showing signs of cristation
Fasciation in Ferns
Several ferns are especially cultivated to be cristate, such as Dryopteris affinis ‘Cristata’ or Asplenium cristata