Silicon (Si) ameliorates the gas exchange and reduces negative impacts on photosynthetic pigments in maize plants under Zinc (Zn) toxicity

This research aimed to (i) measure oxidative stress, (ii) evaluate the responses on gas exchange, (iii) determinate the repercussion on photosynthetic pigments, and (iv) respond if application of exogenous silicon (Si) is efficient to attenuate negative impact on maize plants exposed to Zn toxicity. The experiment employed an entirely randomized design with four treatments (0, 2 mM Zn; 2 mM Zn + 2 mM Si; and 2 mM Si). Hydrogen peroxide and electrolyte leakage were evaluated in root and leaves of maize plants. The gas exchange, net photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency were measured. The pigments such as chlorophylls and carotenoids were measured in leaf. Zn application produced increases in hydrogen peroxide and electrolyte leakage to both tissues, confirming the effects of toxicity. The Zn toxicity + Si presented significant increases of 33.3, 25.2, 15 and 9.8% to stomatal conductance, net photosynthetic rate, transpiration rate, and water use efficiency, respectively, compared to Zn-only treatment. The total, a and b chlorophyll and carotenoids presented non-significant increases, when compared to plants exposed to Zn toxicity. This study revealed the positive contribution of the Si on gas exchange and reduction of the negative effects provoked on chlorophylls and carotenoids in maize plants under Zn toxicity.