Cellular and Morpho-histological Foundations of In Vitro Plant Regeneration

In vitro plant regeneration systems have turned into invaluable tools to plant biotechnology. Despite being poorly understood, the molecular mechanisms underlying the control of both morphogenetic pathways, de novo organogenesis and somatic embryogenesis, have been supported by recent findings involving proteome-, metabolome-, and transcriptome-based profiles. Notwithstanding, the integration of molecular data with structural aspects has been an important strategy of study attempting to elucidate the basis of the cell competence acquisition to further follow commitment and determination to specific a particular in vitro regeneration pathway. In that sense, morpho-histological tools have allowed to recognize cellular markers and patterns of gene expression at cellular level and this way have collaborated in the identification of the cell types with high regenerative capacity. This chapter ties together up those fundamental and important microscopy techniques that help to elucidate that regeneration occurs, most of the time, from epidermis or subepidermal cells and from the procambial cells (pericycle and vascular parenchyma). Important findings are discussed toward ultrastructural differences observed in the nuclear organization among pluripotent and totipotent cells, implying that regeneration occurs from two cellular mechanisms based on cellular reprogramming or reactivation.