Responses Of Festuca Sinensis And Epichlo(?) Endophyte Symbiont To Temperature And Soil Moisture Stress

With the continuous changes of global climate,temperature increase and water shortage have become the main factors limiting plant growth and agricultural production,especially in arid and semi-arid regions.In order to explore the most suitable moisture and temperature conditions of seeds germination and seedlings growth and the role of Epichlo? endophyte in the resistance of Festuca sinensis,different F.sinensis seed lots were collected from alpine meadow on Qinghai-Tibetan plateau and the seeds and seedlings of F.sinensis responsed to different temperature and water stress and effects of Epichlo? endophyte on the resistance of F.sinensis were studied in controlled greenhouse.The main results are as follows:(1)F.sinensis seeds had different germination performance under three different temperatures(15 ?,20 ? and 25 ?)and six water stress conditions(0,-0.2,-0.4,-0.6,-0.8 and-1.0 MPa).The germination rates were the highest at 25 ? whereas were the lowest at 15 ? which suggested higher temperature conditions can improve the seed germination viability.At 15 ? and 20 ? temperature conditions,germination rate,germination potential,germination index and vigor index of seeds under-0.2 MPa water treatment were significantly higher than those of seeds under control and other treatments(P<0.05)which indicated that low concentration of PEG can improve F.sinensis seed vigor under low temperature.However,at 25 ? temperature conditions,the germination rate and germination index of seeds under control treatment were significantly higher than those of seeds under others PEG treatments(P<0.05)which suggested that the PEG inhibited F.sinensis seed germination under higher temperature.The inhibition effects increased with the increase of PEG concentration.The indices including seed germination rate,germination index,plumule length,radicle length,shoot ratio of seeds,seedling moisture content and seed germination drought resistance decreased with the increase of PEG concentration which suggested that high concentrations of PEG has inhibitory on the seed vigor whereas low concentration of PEG had promotion effects on F.sinensis seed under lower temperature condition.(2)The growth performance of F.sinensis seedlings were studied under four soil moisture contents(80%,65%,50% and 35% RSMC,Relative Soil Water Content)and three temperature conditions(15 ?,20 ? and 25 ?).The results showed that the germination rates of F.sinensis seeds were the highest under the condition of 25 ? and 65% RSMC.At 15 ? and 20 ? temperature conditions,the blade width,plant tissue water content,plant height stress index and dry matter stress index of F.sinensis seedlings were the highest at 65% RSMC and were the minimum at 35% RSMC.However,all of the above indices decreased with the decrease of the soil moisture content at 25 ? temperature condition.At all 3 temperature conditions,the root-shoot ratios of F.sinensis seedlings increased with the decrease of the soil moisture content.The seedling root length was the longest at 35% RSMC at 20 ? temperature whereas it was the longest at 50% RSMC at 15 ? and 25 ? temperature and was significantly longer than control and other moisture treatments(P<0.05).Therefore,it is concluded that the conditions of 20 ? temperature and 65% soil moisture content were the most optimal for F.sinensis seedlings growth.(3)Meanwhile,the physiological and biochemical parameters of F.sinensis seedlings were also evaluated beside growth performance.With the decrease of soil moisture content,the peroxidase(POD)activities and the contents of malondialdehyde(MDA),soluble protein,soluble sugar and free proline of F.sinensis seedlings firstly decreased,and then increased at 15 ? and 20 ? temperature conditions,and were the minimum at 65% RSMC.However,these indices of seedlings increased at 25 ? temperature condition and reached the maximum at 35% RSMC.The relative water contents of seedlings at three temperature conditions decreased with the decrease of soil moisture content.With the decrease of soil moisture content,the root activities of the plants increased at 15 ? and 20 ? temperature condition,however,that of the plants increased firstly,and then decreased at 25 ? temperature condition,it was the lowest at 80% RSMC and reached the maximum at 35% RSMC.All of these variations suggest that F.sniensis seedlings could adapt to different ecological environment by regulating their physiological and biochemical reaction.(4)In addition,the growth performances of two ecotypes of F.sniensis endophyte symbiont were also evelated under five soil moisture stress conditions(80%,65%,50%,35% and 20% RSMC).The results showed that the 65% RSMC condition was optimal for F.sniensis seedlings growth,and drought(20% RSMC)and waterlogging(80% RSMC)significantly inhibited the growth of F.sinensis seedlings.The plant heights,tiller number,blade widths,stem diameters,total biomass and root-shoot ratio of endophyte infected(E+)F.sinensis plants were significantly higher(P<0.05)than those of endophyte free(E–)plants under drought and waterlogging conditions which suggested that the presence of endophyte could significantly(P<0.05)promote the plants performance.No significant difference was observed between the two different ecotypes of F.sinensis.These results showed that endophyte infection could enhance the host plant resistance to drought and waterlogging.In conclution,the study clearly demonstrated that optimal temperature and water conditions for F.sinensis seeds germination and seedling growth and evaluated the endophyte positive effects for F.sinensis plant growth.These researches provide the foundation for F.sinensis germplasm selection and breeding.