Evidence of somatic cell reprogramming toward embryogenic competence revealed through morphoanatomical and biochemical transitions in Piper aduncum L.

Somatic embryogenesis represents a well-established example of cellular plasticity in plants, allowing differentiated somatic cells to revert to a totipotent state and regenerate whole plants. In Piper aduncum L., a species of high economic value due to its dillapiole-rich essential oil, large-scale propagation remains limited by inefficient regeneration systems. This study provides integrative evidence of somatic cell reprogramming toward embryogenic competence from adult leaf explants cultured under controlled in vitro conditions. Morphoanatomical analyses revealed that reprogramming began within three days of culture, characterized by hypertrophic nuclei, dense cytoplasm, and perivascular clusters of small isodiametric cells acting as embryogenic niches. Sequential histological and histochemical changes accompanied the transition from callus proliferation to organized somatic embryos, culminating in cotyledonary structures exhibiting all primary meristems. The growth curve of embryogenic calli revealed five physiological phases, with the linear phase (28-49 days) corresponding to the optimal window for subculture and somatic embryo differentiation. Biochemical profiling indicated dynamic redox modulation, marked by transient peaks in antioxidant enzyme activity (SOD, CAT, APX, POD) and controlled lipid peroxidation, suggesting that oxidative signaling functions as a permissive factor during embryogenic induction and differentiation. Together, these findings demonstrate that somatic embryogenesis in P. aduncum arises from a coordinated sequence of cellular and physiological reprogramming events in adult tissues, providing new insights into the developmental plasticity and redox regulation underlying plant regeneration.