Influence of silicon on growth and some physiological attributes of maize (Zea mays L.) under salt stress

Abstract

Three independent experiments were carried out in hydroponic and sand cultures to explore the alleviating effects of different levels of silicon (Si) on growth related attributes and some vital physio-chemical characteristics in two maize cultivars exposed to NaCl-induced salinity stress. Each experiment comprised two maize cultivars (Sadaf and Sahiwal-2002), two salt concentrations (0 and 120 mM NaCl) with varied Si concentrations. Initially, nine Si levels (0, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8 and 3.2 mM) were used for optimization of Si levels in Hoagland’s nutrient solution. Silicic acid [Si(OH) 4 ] was used as a source of Si. Four Si levels (0, 1, 2 and 4 mM) were selected from the optimization experiment, which then were employed for major experimentation. Interactive effect of Si and salt on growth, gas exchange characteristics, plant pigments, chlorophyll fluorescence attributes, biochemical parameters like proline, total phenolics, H 2 O 2 , MDA, antioxidant enzymes (CAT, POD and SOD) and ion accumulation (Na + , Ca 2+ , K + , Cl - and Si) were determined. Exogenous application of Si improved the growth, photosynthetic efficiency, membrane stability, and antioxidant activities and alleviated the toxic effect of Na + ion via improving plant K + , water status, photosynthetic efficiency, membrane stability and activities of antioxidant enzymes. Of various levels, 1 or 2 mM Si were found more effective in this regard under control conditions. However, under stressful environment, 4 mM of Si gave maximum protection against salt stress. Of yield attributes, a positive association was found between Si application and grain yield per plant, although, Si made no change in 100-grain weight. Conclusively, Si had a positive impact on overall health of plant especially under stressed environment and was found effective in the enhancement of salinity tolerance of maize plants.