Effect of light intensity and magnesium deficiency on chlorophyll fluorescence and active oxygen in cucumber leaves

Effects of different light intensities and Mg2+ concentrations on chlorophyll fluorescence and active oxygen in cucumber leaves were studied. The results showed that high light intensity and Mg deficiency induced obvious photoinhibition, which was mainly exhibited by the decrease of the photosynthetic rate (Pn), chlorophyll fluorescence parameters such as Fv/Fm, Fv/Fo, qP and qN, and the increase of O2- producing rate, H2O2 and MDA contents. Adequate shading would help to increase photochemical efficiency of PSII and reduce photoinhibition.