056 | Thidiazuron exposure reprograms metabolic networks with lasting effects on growth and photosynthetic efficiency in Arabidopsis thaliana

Manuela Giraldo-Acosta¹, Giulia Giovanna Salerno², Marino B. Arnao¹, Cinzia Margherita Bertea³, Ada Ricci², Giuseppe Mannino³ | ¹Department of Plant Biology Plant Physiology, University of Murci, Spain; ²Department of Chemical, Life and Environmental Sustainability Sciences, University of Parma, Italy; ³Department of Life Sciences and Systems Biology, Plant Physiology Unit, University of Turin, Italy.

Thidiazuron (TDZ) is a synthetic plant growth regulator with cytokinin-like activity that is extensively used in plant biotechnology and in vitro culture systems. While its influence on plant growth and morphogenetic processes has been well documented, its physiological and molecular impacts during the earliest stages of plant development remain incompletely understood. In this study, we investigated the effects of increasing TDZ concentrations on seed germination and early seedling development in Arabidopsis thaliana, with a particular emphasis on dose-dependent physiological and molecular responses. Seeds of the Col-0 ecotype were germinated under graded TDZ concentrations and examined using an integrated experimental framework combining morphological analysis with assessments of photosynthetic performance and metabolic and hormonal profiling. This multi-level strategyallowed for a comprehensive evaluation of TDZ-induced effects across multiple levels of organization during early development. The results show that low TDZ concentrations do not cause significant alterations in key physiological parameters, indicating that early developmental processes are largely preserved under these conditions. In contrast, higher TDZ levels are associated with progressive changes in cotyledon vascular pattern, the emergence of hormonal imbalances, and a decrease in photosynthetic efficiency, collectively suggesting a reduction in functional capacity during early seedling establishment. Overall, these findings demonstrate that TDZ exert distinct, concentration-dependent effects during germination, defining a continuum ranging from responses compatible with normal development to conditions reflecting increased physiological constraint. This study provides a more refined understanding of TDZ activity and offers a valuable framework for critically evaluating its use in experimental and biotechnological applications.