ROLE OF SILICON IN MITIGATING THE ADVERSE EFFECTS OF SALT STRESS ON GROWTH AND PHOTOSYNTHETIC ATTRIBUTES OF TWO MAIZE (ZEA MAYS L.) CULTIVARS GROWN HYDROPONICALLY

An experiment was conducted in an aerated hydroponic system to examine the ameliorating effects of varying levels of silicon on growth and some key gas exchange characteristics in two maize cultivars subjected to salt stress. Various components of the experiment were two maize cultivars (Sahiwal-2002 and Sadaf), two salt treatments (0 and 150 mM NaCl) and nine Si levels (0, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8 and 3.2 mM) in Hoagland's nutrient solution (full strength). Salicic acid [Si(OH)(4)] was used as a source of Si. After the application of Si and NaCl treatment plants were allowed to grow for 28 days. Exogenously applied varying concentrations of Si significantly improved the growth of both maize cultivars under saline regimes. However, more improvement was observed under non-saline conditions as compared with that under saline conditions. Exogenously applied Si levels in the rooting medium also improved some key plant gas exchange characterstics such as net CO2 assimilation rate (A), stomatal conductance (g(s)), transpiration (E), and leaf sub-stomatal CO2 concentration (C-i) of both maize cultivars both under non-saline and saline regimes. Furthermore, the Si-induced growth improvement in the rooting medium was positively correlated with plant photosynthetic attributes. Of different exogenously applied Si levels, 0.8, 1.6 and 2.8 mM proved to be relatively more effective in enhancing the growth as well as gas exchange attributes as compared with other levels. Overall, exogenously applied Si was found beneficial for improving salt tolerance of maize plants.