Effect of Silicon on Growth, Photosynthesis, Oxidative Status and Phenolic Compounds of Maize (Zea mays L.) Grown in Cadmium Excess

Accumulation of heavy metals due to pollution of the environment, particularly in agricultural ecosystems, can cause serious deterioration of crop yield and quality. In this study, we assessed the effect of silicon on physiological, photosynthetic and stress-related aspects of cadmium toxicity in hydroponically grown maize plants (Zea mays L., hybrid Valentina). One concentration of silicon (5 mM) and two concentrations of cadmium (5 and 50 μM) added to the cultivation medium were tested. Cadmium alone led to a significant growth inhibition and negatively affected the content of total chlorophylls and the efficiency of photosystem II. Especially in roots, application of cadmium resulted in the accumulation of reactive oxygen species and consequent membrane lipid peroxidation. The supplementation of silicon successfully ameliorated the toxic effect of cadmium on maize plants and enhanced growth, some of the photosynthetic parameters and reduced the level of oxidative stress. In plants exposed to higher concentrations of cadmium silicon also reduced its accumulation, especially in roots. Changes in the accumulation of phenolic compounds may indicate the influence of silicon on this aspect of secondary plant metabolism and its importance in the detoxification of heavy metals.