Silicon enhances photochemical efficiency and adjusts mineral nutrient absorption in Magnaporthe oryzae infected rice plants

Silicon (Si) has been verified to play an important role in enhancing plant resistance against pathogens, but the exact mechanisms remain unclear. Two near-isogenic lines of rice (Oryza sativa L.), CO39 (blast susceptible), and C101LAC (Pi-1) (blast resistant), were hydroponically grown to study the effects of exogenous silicon application on the changes of disease incidence, mineral nutrient concentrations, chlorophyll content, and photochemical efficiency in Magnaporthe oryzae infected rice plants. Si amendment in nutrient solution at a concentration of 2.0 mM significantly reduced the disease index of rice plants of CO39 and C101LAC (Pi-1). Silicon application alone had no effects on mineral nutrient contents, chlorophyll content, maximum/potential quantum efficiency (F (v)/F (m)), and the maximum primary yield (F (v)/F (0)) of photochemistry of PS II in healthy rice leaves. M. oryzae inoculation significantly increased the content of K, Na, Ca, Mg, Fe, and reduced the value of F (v)/F (0) and F (v)/F (m) in rice leaves. However, Si treatment suppressed M. oryzae induced increase of mineral nutrient contents, and significantly increased F (v)/F (0) and F (v)/F (m) value compared with Si-deficient infected plants. These results suggest that silicon-enhanced resistance to rice blast is associated with an enhancement of photochemical efficiency and adjustment of mineral nutrient absorption in M. oryzae-infected rice plants.