Research On The Screening Of Germplasm Resources Of Low P And Al Tolerance Of Chinese Fir And Its Related Physiological Mechanism

Cunninghamia Lanceolata(Lamb.)Hook,a fast-growing coniferous tree with high quality timber and good stem shape,and thus is an excellent afforestation tree species in southern China.C.Lanceolata is also an ideal green tree species for landscape because of its high adaptability to marginal field,drought,aluminum toxicity and so on.It can not only greatly improve the urban landscape,but also give full play to the ecological functions of landscape,therefore,play a critical role in landscape.C.Lanceolata is a native plant in acidic soil,and this types of soil is often found in the mountain of southern China,and it was demonstrated that phosphorus(P)stress and aluminum(Al)toxicity were the main limiting factors that impeded the growth of plants in acid soil,therefore,it is of great important to reveal the underlying mechanisms of C.Lanceolata in response to phosphorus and aluminum interactions,and screening some suitable C.Lanceolata families for urban landscape.However,the underlying mechanisms of C.Lanceolata in response to P and Al coupled stress remain unknown.Therefore,in order to make qualitative analysis on the tolerance capacity of C.Lanceolata for low phosphorus and aluminum stress,72 C.Lanceolata families were investigated in this study,the P and Al tolerant capacity of 72 families of C.Lanceolata were classified based on the membership function method,and sequentially analyzed the growth of C.Lanceolata,the related indexes of oxidative damage in different C.Lanceolata families.Then,2 C.Lanceolata families with different tolerance to low phosphorus and aluminum stress were selected to study the underlying tolerance mechanism of C.Lanceolata under P and Al coupled stress,and providing a theoretical basis for the selection of C.Lanceolata in garden planting,and thus promoting its application in the urban landscape construction.The main results are as follows:1.Membership function was used to evaluate the tolerance of C.Lanceolata in yellow soil by comparing the biomass(ground.diameter,plant height,lateral branch)among 72 C.Lanceolata under families.The results showed that the biomass of No.3,No.26,and No.5 families were significantly higher than the average value of 72 families,they were 24.44%,24.22%,8.85%higher than the average value,respectively.Whereas,the biomass of No.22,No.55,No.12 of C.Lanceolata families were significantly lower than the average value,they were 22.00%,28.67%,31.94%lower than the average value,respectively.Therefore,the preliminary results of this study showed that 3 C.Lanceolata families including No.3,No.26,No.5 showed relative strong tolerance to yellow soil,while the other 3 C.Lanceolata families including No.22,No.55,No.12 showed relative poor resistance to yellow soil.2.The content of soluble protein,MDA in leaf and the root activity of six C.Lanceolata families under different treatments(P without Al(ck),P and Al,Al without P,without P and Al)were analyzed by physiological methods.The results showed that there were significant differences in MDA content,root activity,soluble protein content among six C.Lanceolata families under different stress times and conditions.The MDA contents of six C.Lanceolata families showed a tendency to increase first and then decreased after they reach the peak values.The soluble protein content was increased with time after treatment,while an opposite tendency was observed for root activity.The tendency and value of other indexes varied greatly when the C.Lanceolata family and the stress time were different.The results showed that the tolerance of 6 C.Lanceolata families to P and Al stress was:No.3>No.26>No.5>No.55>No.22>No.12,which was r similar to those of biomass evaluation.3.According to the preliminary screening results,2 C.Lanceolata families No.3(tolerance to-P+Al)and No.12(sensitive to-P+Al)were selected for further studied.The role of enzyme activities in AsA-GSH cycle were analyzed in 2 different C.Lanceolata families under P and Al coupled stress(4 treatments including P without Al(ck),P and Al,Al without P,without P and Al).The results showed that there were significant differences in the activities of antioxidant enzymes(CAT,POD,SOD and PPO)and ASA-GSH cycle related enzymes in No.3 and No.12 of C.Lanceolata.Compared with the CK,the activities of protective enzymes,GR,APX,MDAR,and DHAR of No.3 and No.12 were increased,and the increase of No.3 was higher than No.12 under different treatments.ASA and DHA content were increased,an increase of ASA content that No.3 is greater than No.12,the content of DHA increase less than No.12,Under P and Al,Al without P,without P and Al treatments the ASA/DHA content of No.3 and No.12 were 0.85,1.60,1.60,and 1.99,1.88,1.89.GSH and GSSG content were increased under P and A1 treatment,an increase of GSH content that No.3 is greater than No.12,the content of GSSG increase less than No.12.Under Al without P,without P and Al treatments the GSH and GSSG content were decreased,and an decrease of GSH content that No.3 is less than No.12,the content of GSSG increase greater than No.12,Under P and Al,Al without P,without P and Al treatments the GSH/GSSG content of No.3 and No.12 were 3.35,4.77,5.09 and 5.64,7.25,5.32.The higher antioxidant enzyme activity,the greater the ASA/DHA and GSH/GSSG,the stronger the ability of antioxidant stress of Chinese-fir families.The results showed that the No.3 could increase the antioxidant capacity of ROS by increasing the value of antioxidant enzymes and antioxidants,and then enhance its tolerance to P and A1 coupling stress.