Physiological Response Of Bothriochloa Ischaemum Under Different Negative Pressure Water Supplying

With the shortage of water resources,how to realize the breeding and precise irrigation of drought-resistant varieties have become the key research topics and urgent problem in agricultural science.Bothriochloa ischaemum,the constructive and dominant species of warm shrub rangelands in Shanxi Province,is of great significance in rehabilitation of degraded rangelands,artificial grassland construction and ecological construction.However,their applications are seriously restricted because of shortage of water resources.In view of this,there is a need for the research of tolerate drought adaptability and water utilization,which provide theoretical basis for the breeding of high stress tolerance varieties.This experiment was designed to determine the changes in growth properties,osmotic adjustment substances and key antioxidant enzymes of 10 population of wild Bothriochloa ischaemum,and to screen out two populations with distinct difference in drought resistance.And then,their changes in osmotic adjustment substances,photosynthetic characteristics,kinetic characteristics of chlorophyll fluorescence and antioxidant capacity under drought stress were analyzed,to verify the drought resistance of two populations of Bothriochloa ischaemum and reveal their mechanism in response to drought stress.Main results are as follows:(1)Drought stress was was carried out on10 wild populations of Bothriochloa ischaemum with 75%~80%,60%~65%,45%~50% and 30%~35% of soil water content,and their changes in growth properties,osmotic adjustment substances and key antioxidant enzymes were analyzed.The results showed that their plant height declined,but their root shoot ratio,contents of Pro,SS and MDA,and activities of SOD and POD increased.The order of their comprehensive drought resistance was FY>LF>TG>XX>LL>ZY>YS>PD>HY>YQ.(2)NPWSCPD was used to carry out drought stress on FY and PD population of Bothriochloa ischaemum with 75%~80%,60%~65%,45%~50% and 30%~35% of soil water content.The results showed that NPWSCPD could guarantee the consistency of drought stress conditions,and there was a significant negative correlation between the water supply tension and soil water content.Under the same water supply tension,the total water consumption of FY population of Bothriochloa ischaemum was lower than PD population,while their rate of green leaf and RWC were higher than PD population.(3)NPWSCPD was used to carry out drought stress on FY and PD population of Bothriochloa ischaemum with 75%~80%,60%~65%,45%~50% and 30%~35% of soil water content.The results showed that the SPAD,Pn,Gs and Tr decreased in both populations with the increase of water supply tension,but their Ci was improved.The WUE of FY population was enhanced with the increase of water supply tension,but the PD population declined,and the WUE of FY population was higher than PD population under the medium and high water supply tension.This indicated that non-stomatal factor was the main reason for the decrease of Pn.The increase of drought stress led to the decrease of light saturation point and intercellular CO2 saturation point in the leaves of Bothriochloa ischaemum.(4)NPWSCPD was used to carry out drought stress on FY and PD population of Bothriochloa ischaemum with 75%~80%,60%~65%,45%~50% and 30%~35% of soil water content.The results showed that the ΦPSⅡ、Fv/Fm、q P and ETR of FY and PD population of Bothriochloa ischaemum dereased with the increase of water supply tension,and the decreasing amplitude of FY population was lower than PD population.This indicated that the photosynthetic activity of FY population was higher than PD population.The outer membrane of their leaf cells was destroyed,the inner membrane was disintegrated,the matrix was extravasated,the grana lamellae were twisted and disordered,and the chloroplasts dissociates into the center of the cells.FY population of Bothriochloa ischaemum had more starch grains under the high water supply tension,while PD population of Bothriochloa ischaemum had almost no starch grains,which was indicating that the drought stress damage of FY population was less than PD population.(5)NPWSCPD was used to carry out drought stress on FY and PD population of Bothriochloa ischaemum with 75%~80%,60%~65%,45%~50% and 30%~35% of soil water content.The results showed that the contents of Pro,Sp and SS were improved in both populations of Bothriochloa ischaemum with the increase of water supply tension,and the amplification in FY population was higher than PD population.Soil water content and RWC of leaf decreased with the increase of water supply tension,but the PMP and MDA contents of leaf increased,and the amplification in FY population was lower than PD population.The activities of CAT,POD,SOD,APX and GR also declined with the increase of water supply tension,but the amplification of As A and GSH in FY population was higher than PD population.(6)It was showed that the drought resistance of FY population was stronger than PD population by the comprehensive analysis of growth performance,antioxidant system,photosynthetic characteristics,osmotic adjustment substances and chlorophyll fluorescence parameters.