Histological Approach to the Study of Morphogenesis in Callus Cultures In Vitro: A Review

Abstract

The use of in vitro callus cultures as experimental model systems allows us to get closer to understanding the patterns and features of morphogenesis in intact plants. In this regard, the problem of realizing the morphogenetic potential of callus cells due to their pluri- and totipotency properties is of great interest. To solve this problem, it is important to use the histological approach, which involves studying the structures of developing tissues, organs and organisms in their interactions and relationships. This review article analyzes data devoted to the study of the histological features of formed primary morphogenic calli (formation of morphogenetic centers and superficial meristematic zones), as well as the in vitro morphogenesis pathways in calli that lead to the formation of regenerants (de novo organogenesis and in vitro somatic embryogenesis). The terminology used is considered. Some questions for discussion are raised. The opinion is expressed that histological (structural) studies should be considered as a methodologic basis for further investigation of various morphogenetic scenarios in in vitro callus cultures, especially in economically valuable plants and for biotechnological purposes.

Ultrastructure, CO2 Assimilation and Chlorophyll Fluorescence Kinetics in Photosynthesizing Glycine max Callus and Leaf Mesophyll Tissues

“…In contrast to the compact callus tissue, the friable callus tissue was composed of cells with sharp, uneven edges (Figure 3). The compact callus tissue had inclusions of densely located cells (Figure 3), which are commonly referred [31] to as meristemoids. Chloroplasts with a clearly exhibited granal structure were observed in the cells of the compact callus tissue; however, these cells showed strongly marked signs of senescence-very thin layer of cytoplasm and cytoplasm sequestration, rupture of the vacuolar membrane, delamination of the cytoplasm from the cell wall and targeting of organelles (including chloroplasts) into vacuoles, with a low number or absence of mitochondria (Figure 4A,B,D,E).…”

Morpho‐histology of co‐occurrence of somatic embryos, shoots, and inflorescences within a callus of Limonium ‘Misty Blue’

“…This approach is an important tool for understanding structural changes at the cellular level during genetic reprogramming for organogenesis and somatic embryogenesis. This study also revealed the dedifferentiation process in competent cells of highly differentiated mature tissues, identified the zone within the callus from which the acquisition of pluripotency or totipotency occurs, and, most importantly, revealed the spatial and temporal development of vegetative shoots, floral organs, and somatic embryos (Kruglova et al, 2023). Moreover, anatomical studies during the regeneration process will explain the role of programmed cell death (PCD) and polyphenol accumulation during the origination and pattern formation of shoot buds and somatic embryos.…”

“…(Awal et al, 2013) and Arabidopsis thaliana (Cheng et al, 2010), but no one has previously reported co‐occurrence of shoot, flower, and somatic embryo differentiation from a single piece of callus in any plant system. The simultaneous differentiation of vegetative and reproductive organs, together with somatic embryogenesis, depends on differential genetic reprogramming of existing somatic cells of the callus and the acquisition of either cellular totipotency or pluripotency from the stem cell niche (Kruglova et al, 2023). To learn the tangible facts, it is pertinent to study the ontogeny of the redifferentiation process based on sequential histological observations.…”

The Influence of Light Intensity and Duration on the Formation of Primary and Secondary Metabolites in Tea Plant Cell Culture

“…These are "young" cells that are formed after the transfer of callus to a fresh nutrient medium [49]. It is believed that their formation is due to the functional activity of the so-called "meristematic zone" of plant calluses [50].…”