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Cristation (Forma cristata) [ Botany - Morphology ]  
Synonym: Fasciation
Adjective: Crested - Cristata
Noun: Crest

Dictionary of botanic terminology
index of names

       
    Fasciation or cristation is an abnormal development of an apical meristem characterized by indeterminate proliferative growth. A plant becomes crested when its apex develops laterally from a linear meristem rather than a single point  
       
From the Latin word “fascia”, meaning “a band”.
 

Rebutia heliosa "cristata" Clone A
(Photo 1)
Rebutia heliosa
 forma cristata
This  crest clearly shows the elongated line of growth (due to a linear meristem) at the tip.

Fasciation or cristation is a widespread phenomena that may randomly affect vascular plants both in nature and in culture. Out of 290 families the fasciations were found at least in 107 of them. There are no direct confirmation of absence of fasciations in any of taxonomic groups of vascular plants.
A fasciation (abrupt changes of organ forming activity of meristems resulting from somatic mutations) is an abnormal enlargement or coalescence of a shoot tips ( not a disease) in which a single apical meristem has become unusually broadened and flattened , suggesting many stems have fused together (Photo 1), this establish the following unlimited growth,
As a result the shoots have axial symmetry instead of central symmetry.  The plants reached take initially the form of a fan, then undulate, and end up resembling brains (Photo 2). Side shoots are usually absent or remain small and undeveloped. It is especially prevalent in species with indeterminate growth patterns. Although there is another much rarer type, characterised by a ring-shaped growing point, which produces a hollow shoot (ring fasciation).
Some cristation are real living sculptures, sought after by collectors, coveted by plant amateurs, and widely cultivated by commercial grower, they look very outstanding when potted and certainly attract a lot of attention.
The plant showing this abnormal growth are indicated as "forma cristata" or  "f. cristata" following the name of the species
   
Cause of Fasciation

Fasciation can be caused by a variety of natural and artificial agents. It may follows disturbance of the growing point by insects, mites, fungi (e.g. white rusts), and other agents.
The exact nature of the disturbance is unknown, but it appears to involve the hormone balance in the plant. For instance, the bacterium Corynebacterium fascians produces cytokinins and causes a range of symptoms, including witches' brooms and fasciation. Fasciations have also been reported to occur spontaneously.


(Photo 2)
Mammillaria theresae
forma cristata

  1) Genetic Fasciation
It is not truly known if the fasciations are inherited. However, the tendency toward fasciation is transmissible by budding and grafting once the plant develops a fasciation. Growers who prune off fasciated branches often find this condition returns with the development of new branches. At least in some occurrences fasciation is controlled in plants by genes. Many species exhibit true-breeding fasciated lines, although the expression of the character is very dependent on environmental conditions - especially temperature and nutrition. Because the gene conditioning fasciation exhibits incomplete penetrance, the character may assume any of many degrees of expression. The cockscomb celosia (Celosia argentea var. cristata) is an excellent example of a plant with inherited fasciation.
 
  2) Physiological Fasciation  
    A) Natural Environmental Factors  
      I Attack by Insects. Several insect species have been found to produce fasciation.  
      II Pressure. Underground shoots that pierce the ground, such as asparagus, tend to become fasciated.  
      III Seasonal Influences. Time of sowing may influence the degree of fasciation, with earlier sowing appearing to produce larger numbers of fasciated plants.  
      IV Crowding:  has often been reported to produce a decrease in the percentage of fasciated plants.  
      V Temperature. Low temperature followed by high temperature causes fasciation in Hyacinthus and may be a cause of fasciation in other plants.  
      VI Mineral Deficiency. Zinc deficiency is known to cause fasciation.  
    B) Artificially Applied Factors  
    I Decapitation of Seedlings and Defoliation: Amputation of the main stem of seedlings induces fasciation in several species.  
    II Wounding of the Growing Point: Wounding causes fasciation as well as all kinds of abnormalities.  
    III Ionizing Radiation: (X-rays and gamma-rays).  
    IV Infection with Fungi, Bacteria, and Viruses  
    V Polyploidizing Agents (colchicine, morphine, phenyl-urethane, etc).  
    VI Nutrition Good nutrition, including high rates of nitrogen, increases the occurrence of fasciation.  
    VII Water Shortage Plants with indeterminate inflorescences when kept under drought conditions prior to flowering and then subjected to heavy watering and high nutrient levels will produce fasciations  
    VIII Application of Growth Regulators and Herbicides: TIBA (2,3,5-triodobenzoic acid), for example, induces fasciation, particularly ring fasciation, and many other abnormalities, including distortions and fusion of organs.  
    IX Photoperiod: Fasciation may be induced by increasing or decreasing the photoperiod - the lenght of day experienced by the plants.
 
 
Cristation in cactus and succulents:

Turbinicarpus pseudopectinatus "inermis Cristatus" a very nice spineless crested form
(Photo 3)
Turbinicarpus pseudopectinatus forma inermis cristata

Cristation is a quite frequent phenomenon in Cactaceae ( reported in more than 50 genera) and also in many other succulents family like in Euphorbiaceae, Crassulaceae, Asclepiadaceae, etc.. A pure cristation is also completely different then monstruosity, where axils (areoles) are multiple-activated and the apical meristem stopped growing.
All column-like and globular cacti, as well as Opuntias, can be touched by this anomaly growth form which remains however rare because it cannot be caused. One did not find yet a cristation for all the existing species.
Cactus horticulturists and collectors believe that cristation results from somatic mutation(s) at the apical meristem region of the main stem or branches and that a predilection for occurrence of this mutation is heritable.

As a result of unlimited growth of linear meristem (see: photo 1) the stem gets flattened, areolae with spines are situated on all the surface of the crests. The number of ribs and/or of parastichs (spiral lines formed by areoles) increases but the structure of areolae themselves does not practically change. Depending on the age there are fan-shaped (Photo 6), wavy and brain-shaped crests. More thick crests seldom grow into brain-shaped (e.g. crests of Carnegia gigantea). All fasciated species grow faster than normal ones which corresponds to the opinion of most authors, the increase of photosynthesizing surface leads to better carbon nutrition and faster growth of fasciated plants. Crests may remain at any stage for a long time. But at the stage of brain-shaped crest when the curves begin to crowd defasciation (Photo 4) occurs rather often. That is the linear meristem turns into a number of small apical meristems that form normal shoots. Seldom defasciation occurs without any reason at an earlier stage of the development of the crest. In general with age meristem gets less active or not active at all. The growth continues only at some parts of linear meristem. Thanks to this process the upper surface becomes uneven. The more active parts are usually situated at its ends. This type of developing crest prevails among cacti, and for a long time it was considered to be the only possible.


(Photo 4)
Mammillaria luethyi
forma cristata

an example of crest defasciation


(Photo 5)
Strombocactus disciformis
forma cristata

Juvenile and mature structure in response  to the use of different grafting stocks.

Many authors affirm that the crest of cacti has another specific feature. In spite of their rather large size the areolae frequently kept their juvenile structure and are situated like at the seedlings of the species.
Consequently the physiological age of crest may not depend on its real age and be determined by the stage of the development at which it appeared. It is quite possible that the crest that appeared at a juvenile plant will not be able to bloom during its life-time.

But this thesis is not based on a correct observations, the apparent age of the crest depends mainly by the hormonal balance furnished by the grafting stock. It is a well known phenomenon that crest grafted on different stocks may be very different one from each other.
The fact that crest forms flowers rarely is in part due to the consuetude to graft the crest on strong stock that enhance only a fast growth and delete the natural maturation and flowering. (photo 5)
In the ontogenesis a crest can appear any time, but development of crests at large columnar cactus species ( such as in saguaro Carnegia gigantea) in the early stages of ontogenesis is unlikely. On the other hand small species may crest early already at the cotyledons stage
That means fasciations can take place even in the first days of a seedling or at the stage of the forming of the embryo in the seed. As practice shows when cactus fanciers grow cacti out of seeds fasciations often take place at germs and juvenile plants especially when the regime changes (temperature, humidity, grafting onto a strong stock). It also takes place in any growing phases without any apparent reasons.
Fasciation in a taxon is clearly correlates with the degree of succulent characteristics of stems. Among widely spread fasciated plants there are many members the most advanced subfamily Cactoideae, which grows in arid conditions and are remarkable for the high degree of succulence. While primitive subfamily Pereskioideae  which grow in the conditions of sufficient or excessive humidity, have a high percentage of photosynthesizing surface to the volume of the plant and have almost no fasciations. A larger number of fasciations is found among   xerophytes as compared with hydrophytes were mentioned earlier for other families as well. Among succulents the frequency of fasciations is most likely to be at evolutionally advanced taxa with highly specialized vegetative organs. It is obvious that environmental conditions are more important for the appearance of fasciations than the origin of the species with high frequency of fasciations.


(Photo 6)
Geohintonia mexicana
forma cristata

 


(Photo 7)
Echeveria coccinea
San Bartolo Co. Hidalgo,
Mexico forma cristata

Cultivation of crested cacti and succulents.
Cultivation of the cristate forms of cacti is worthy of a special mention because an accidental appearance of a crest happens quite often and these plants attract attention of collectors thanks to their prominent ornamental features. Furthermore the crested forms can be usually reproduced vegetatively without difficulties Many crests should be kept on the dry side, in other words, grown hard. Too much water and/or fertilizer can cause cracks and spreading. Trimming any normal shoots off helps the crested form grow better and truer to form, but sometimes these normal shoots can crest again after some normal growth. Cuttings from crested cactus should be grafted for best results. Cuttings from other crested succulents can be replanted after the normal waiting period. Keep these very dry for at least a week or preferably two weeks and on the dry side during their normal growing cycle. For euphorbias, this would be in the Autumn.
For some leaf succulents it is sufficient to have any part of the mother plant - a leaf or even an ordinary, non-crested shoot (Photo 7) in order to reproduce crested form. In other cases only a fragment of the crested shoot is suitable for reproduction whereas leaves and normal, not crested shoots don't inherit desirable qualities.

 


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