Relationship between photosystem activity and ultraweak luminescence excitation in Cerasus humilis leaves under low...

This study examines how low light stress affects photosystem (PS) activity and ultraweak luminescence (UWL) in Cerasus humilis (Bge) Sok (C. humilis) leaves, focusing on their interplay under varying light intensities. To clarify the impact patterns of low light stress on PS activity and UWL intensity in C. humilis leaves, and to elucidate the correlation between PS activity and UWL under varying light intensities. In this experiment, C. humilis potted seedlings were used as materials. Light treatments with different shading levels were applied, including mild low light stress (L1, 85 % shading) and severe low light stress (L2, 96 % shading). PS activity in leaves and UWL intensity were determined. The variation patterns and correlations between PS activity and UWL intensity were analyzed. Results showed: PS Activity: L1 reduced energy utilization efficiency but not PS activity; L2 significantly suppressed PS activity, disrupted thylakoid membranes, lowered PS II efficiency, and impeded electron transport. UWL Intensity: Both treatments reduced UWL, with L1 causing a slight decline and L2 a drastic reduction. Correlation: UWL intensity positively correlated with PS activity parameters, including PS II quantum yield, photosynthetic performance indices, and energy transfer efficiency. The PS activity in C. humilis leaves is closely associated with UWL generation, with UWL intensity decreasing as PS activity declines. While L2 treatment significantly weakened UWL by suppressing PS activity and PS II photochemical reactions, L1 had negligible effects on both parameters. This finding provides new insights into plant photostress response mechanisms and the physiological significance of UWL.