Silicon and cadmium interaction of maize (Zea mays L.) plants cultivated in vitro

The aim of the present study was to assess the effect of cadmium (100 µM Cd) and/or silicon (5 mM Si) on the maize hybrid Reduta cultivated for 15 days in an isolated in vitro conditions. The growth parameters, Cd and Si accumulation, the expressions of the genes for Si transporters (ZmLsi1, ZmLsi2, and ZmLsi6), the root developmental changes and activities of antioxidant enzymes (guaiacol peroxidase, catalase, superoxide dismutase) were investigated. Silicon and/or Cd application altered the maize primary root development in terms of growth and apoplasmic barriers; lignification and suberisation of the exodermal and endodermal cell walls were enhanced both in Cd, Si, and CdSi treatment. The content of Cd which was predominantly accumulated in the roots decreased in the CdSi treated roots and in the 1st leaf in comparison with the Cd treatment. On the contrary, maize plants accumulated Si mostly in the leaves with no differences between the Si and CdSi treatment. The expression of the gene for Si influx transporter (ZmLsi1) was in the roots up-regulated due to Cd (Cd and CdSi treatment), but down-regulated in the Si treatment. The relative expression of the gene for Si efflux transporter (ZmLsi2) was regulated positively due to the Si, Cd and CdSi treatment with the peak in the CdSi treatment. A strong up-regulation of the ZmLsi6 which encodes the protein responsible for Si releasing into the leaves was in the 2nd leaf in the Si and Cd treatment.