Callusogenesis as an in vitro Morphogenesis Pathway in Cereals

Callus is an integrated system formed both exogenously (as a result of proliferation of surface cells of different plant tissues) and endogenously (deep in tissues). Initially, callus consists of homogeneous cells gradually transforming into a system of groups of heterogeneous cells with species-specific morphogenetic potencies, which are realized via various pathways of morphogenesis. In this review, issues associated with studying the formation of calli in in vitro cultures of immature anthers and embryos of cultivated cereals are analyzed. Distinguishing the critical stages of callusogenesis is proposed. The features of hemmorhizogenesis in vitro as a type of organogenesis in calli are considered. The concept of the versatility of the processes of plant morphogenesis in vivo, in situ, and in vitro proposed by T.B. Batygina (1987, 1999, 2012, 2014) is confirmed. The prospects of the approach to calli as model systems for studying various problems of plant developmental biology are discussed.