Abstract

Photosynthesis, the fundamental process of energy conversion, is critically dependent on the efficient and regulated flow of electrons within the thylakoid membranes of chloroplasts. Plants have evolved diverse strategies to adapt their photosynthetic machinery to varying light environments, particularly contrasting shade and high-light conditions. This study investigates the differences in electron transport processes within the chloroplast membranes of two contrasting *Tradescantia* species: a shade-tolerant species (*T. fluminensis*) and a light-loving species (*T. sillamontana*). Using biophysical techniques, including chlorophyll fluorescence and P700 measurements, we comparatively analyzed the photosynthetic electron transport chain (PETC) activity, the efficiency of Photosystem I (PSI) and Photosystem II (PSII), and the regulatory mechanisms like cyclic electron flow (CEF) under varying light intensities. The results indicate that the shade-tolerant species exhibits a higher quantum yield of PSII and a more stable PETC under low light, while the light-loving species demonstrates superior capacity for non-photochemical quenching (NPQ) and a more robust CEF to protect the photosynthetic apparatus from photo-oxidative damage under high light. These findings reveal distinct membrane-level adaptations in electron transport regulation that underpin the ecological success of these species in their respective light niches, contributing to a deeper understanding of plant photoprotection and photosynthetic plasticity.