Protocorm Regeneration and Protocorm-Like Bodies

Protocorm readily regenerates, giving rise to protocorm-like bodies (PLBs) when cultured using suitable media and appropriate levels of plant growth substances. The relative ease of manipulation and high regeneration frequency make the protocorm a useful experimental system for studying the regeneration process in plants. Single cells or multicell groups from epidermal and subepidermal cell layers are primarily responsible for PLB formation in orchids using various explants. We envisage that PLB somatic embryos will first be initiated during regeneration. PLB somatic embryos are small globular cell masses with a dense cytoplasm. The somatic embryos soon “germinate,” giving rise to PLBs, a process analogous to the precocious germination of immature zygotic embryos. Thus, PLBs are germinating somatic embryos comparable to a protocorm from a zygotic embryo, with the primary goal of forming a shoot and becoming a functional seedling. Recognizing the presence of the PLB somatic embryo stage and how these embryos develop into PLBs will aid in our understanding of the regeneration process and PLB development.