Origin, morphology, and anatomy of fasciation in plants cultured in vivo and in vitro

Abstract

Fasciation (or cristation) is a variation in the morphology of plants, characterized by the development of various widened and flattened organs. According to origin, fasciations are classified as physiological or genetic but comparatively little is known on their epigenetic or genetic nature at the molecular level. Physiological fasciations are caused by natural environmental factors or artificial treatments including exogenously applied growth regulators. CLAVATA genes (CLV1, CLV2, and CLV3) have been shown to be the main genetic factors associated with fasciation. Despite the great variety of fasciation-induction factors, fasciations have similar features of development during the first few weeks, i.e., increased mitotic activity and size of the apical meristem and an altered arrangement of cells in the meristematic zones, often leading to an increased number of organs and changes in the plastochron. The enhanced activity of apical meristem and cambium results in a significantly increased circumference of the stem and enlarged proportions of pith and cortical parenchyma, associated with a delayed differentiation of the vascular tissues. An elliptical or irregular shape of the cross section of a fasciated organ corresponds to a similar shape of the vascular cylinder. Later stages of the ontogenic development of fasciations are species-specific, may depend on the origin of fasciation, and in some cases may lead to deviations from the normal structure of the epidermis, shape of leaves, as well as altered development of axillary buds. Studying the causes and patterns of development of fasciations could provide a better understanding of the growth processes in the vegetative apex. Further anatomical and physiological research should focus on the structure and activity of meristems of fasciated shoots, as well as on their transcriptome analysis, in order to better understand the pattern of fasciation development.

Molecular identification of phytoplasmas in fasciated cacti and succulent species and associated hormonal perturbation

“…The circumferences of fasciated tissues are several times greater than those of the symptomless ones due to increases in rates of cell growth and cell division (Iliev & Kitin 2011). These fasciation characteristics indicate perturbations in plant hormonal balance.…”

“…Similarly, fasciation in pea is characterized by abnormal enlargement of the stem apical meristem leading to distortions in shoot structure (Sinjushin & Gostimsky 2006. Fasciated shoots of Betula pendula induced in vitro as well as Prunus avium and Fraxinus excelsior formed flattened stems with densely arranged lanceolate leaves that were dramatically increased in size (Kitin et al 2005;Mitras et al 2009;Iliev & Kitin 2011). …”

“…It occurs in the morphology of plant organs and typically involves broadening of the shoot apical meristem, flattening of the stem, and changes in leaf arrangement (Iliev & Kitin 2011). It has been noted that many biotic and abiotic causes lead to the development of fasciated forms including fungal and nematode infections (Stange et al 1996) and mineral deficiency; zinc deficiency is known to cause fasciation (Rance et al 1982), temperature fluctuation (Binggeli 1990), chemical mutagens (Soroka & Lyakh 2009), and mutations (El-Banna et al 2013).…”

“…All column-like and globular cactican be touched by this anomaly growth form which remains, however, rare. According to origin, fasciations are classified as physiological or genetic, but comparatively little is known on their epigenetic or genetic nature at the molecular level (Iliev & Kitin 2011). Previous studies on fasciation of cacti and succulent plants focused mainly on the causative factors of fasciation (Snyder & Weber 1966;Boke & Ross 1978;Werner 1988;Bourque & Pierson 1998).…”

Strategy for shoot meristem proliferation in plants

“…This morphological abnormality is well known as fasciation, which is observed in various plant species in a natural environment as well as under laboratory conditions. 19 In addition, fasciated shoots are also found in several garden varieties, such as Japanese fantail willow (Salix sachalinensis) and feather cockscomb (Celosia cristata).…”