Effect of silicon on chlorophyll content and gas exchange characteristics of switchgrass under NaCl stress

The effects of silicon on chlorophyll content and gas exchange characteristics of two different ecotype varieties switchgrass (Panicum virgatum) including Alamo(lowland) and Cave-in-Rock(upland) under salt stress were investigated. The concentrations of NaCl and Si NaSiO39H2O were 0, 50, 100, 150 mmolL-1 and 0, 0.5, 1, 2 mmolL-1, respectively. The results showed that the chlorophyll contents of Alamo decreased significantly (P0.05) under salt stress, but that of Cave-in-Rock slightly increased. The net photosynthetic rate (Pn) and stomatal conductance (Gs) of Alamo increased at 50 mmolL-1 NaCl level, then decreased at 100 and 150 mmolL-1 levels of NaCl concentrations. Pn, Gs and intercellular CO2 concentration (Ci) of Cave-in-Rock decreased significantly (P0.05) with increasing NaCl levels. Optimal concentration of exogenous silicon addition had alleviated the reduction of chlorophyll and improved gas exchange ability of Alamo and Cave-in-Rock under salt stress. In our study, 1-2 mmolL-1 was the optimal concentration of silicon (Si).