Effect Of Exogenous Silion On Physiology And Ecological Stoichiometry Characteristics Of Switchgrass Seedlings Under Salt Stress

To study the effect of silicon on physiological and ecological stoichiometry characteristics of switchgrass under salt stress, reveal the salt tolerance mechanism of switchgrass. We used sand culture method, set up the concentrations of Na Cl and Si were 0, 50, 100, 150 mmol/L and 0, 0.5, 1, 2 mmol/L, respectively and used two switchgrass varieties “Alamo”(lowland) and “Cave-in-Rock”(upland) to measure a series of indexes include physiological and ecological stoichiometry characteristics. The indexes were including the leaf relative water content(RWC), plant height, chlorophyll contents, gas exchange parameters, malonaldehyde(MDA) content, proline(Pro), the producting rate of O2·-, superoxide dismutase(SOD) activity, peroxidase(POD) activity, catalase(CAT) activity in switchgrass leaves and the content of nitrogen(N), phosphorus(P), potassium(K) and sodium(Na) and the ratio of N:P and K:Na in switchgrass roots. The results showed that:(1) The RWC, plant height, gas exchange parameters of two ecotype switchgrass and the chlorophyll contents of “Alamo” decreased under salt strss, but for “Cave-in-Rock”, the chlorophyll contents slightly increased. 1-2 mmol/L exogenous silicon addition had alleviated the reduction of RWC, chlorophyll and improved gas exchange ability of two ecotype switchgtass and enhanced the plant height of “Alamo” under salt stress. However, there was no affected of silicon on plant height of “Cave-in-Rock” under salt stress.(2) The producting rate of O2·-, MDA content, Pro increased and SOD, POD, CAT activity decreased with increasing salt concentrations. 1-2 mmol/L silicon addition had increased Pro and SOD, POD, CAT activity, decreased producting rate of O2·- of two ecotype switchgrass and decreased the MDA content of “Alamo”. But the effect of silicon on MDA content of “Cave-in-Rock” was not significant.(3) In two ecotype switchgtass roots, the content of N, P, K and the ratio of N:P and K:Na decreased, while the Na content increased under salt stress. After adding silicon, the Na content of Alamo decresed, the N, P and K content of two ecotype switchgrass enhanced and the ratio of N:P of Alamo increased. But there is no significantly effect of the ratio of K:Na of Alamo, the Na content and the ratio of N:P and K:Na of Cave-in-Rock. Meanwhile, the different ecotype switchgrass had different optimal silicon concentration. 1-2 mmol/L was beter for Alamo and 0.5-1 mmol/L was beter for Cave-in-Rock.Therefore, salt stress had affected the physiological indexes and ecological stoichiometry of switchgrass, exogenous silicon addition had alleviated water state, increased chlorophyll contents and light use efficiency, decreased producting rate of reactive oxygen species and peroxidation of membrane lipids, enhanced the antioxidase activities, osmotic adjustment and elements balance of switchgrass under salt stress. In our study, 1-2 mmol/L silicon was better than others, although there was lightly significantly in two ecotypes switchgrass.