Eco-physiological Responses And Metabolomics Analyses Of Dalbergia Odorifera Seedlings Under Waterlogging And Salt Stress

Dalbergia odorifera T.Chen.,is one of the important redwood species in China.Its heartwood can be used for traditional Chinese medicine,possessing important economic and medicinal values.Understanding its tolerance and eco-physiological responses to salt condition,and waterlogging with tap water and salt water by the controlled experiments is of great importance in providing theory foundation and research reference for its expanding cultivation,which could relieve the imbalance between its supply and demand and eventually maximize its comprehensive benefits.Therefore,4 treatments including the control（CKM）,waterlogging with tab water（WM;5 cm above the soil surface）,salt treatment（SM;200 mM NaCl）and waterlogging with salt water（SWM;100 mM NaCl）were performed to get a well understanding of the eco-physiological responses of D.odorifera seedlings to these stress conditions mentioned above.Results show that:（1）after6-day treatments,all stress conditions decreased the leaf stomatal conductance（g_s）,net photosynthetic rate（Pn）,leaf water potential（Ψ_l）and relative water content;at the level of leaf phytohormone,IAA content was downregulated in WM and upregulated in SM,ABA content was upregulated in all treatments,ZR content was downregulated in SM and SWM,and GA₃ was upregulated in WM;（2）after 30 days,all seedlings in stressed conditions presented the decreased values in terms of leaf area and shoot height,and the survival ratio of the seedlings in SM and SWM was 83.33%and 66.67%,respectively;All seedlings in WM survived after130-day treatment.All these results would lay a foundation for the future work in its introduction and extended cultivation.Besides,the metabolomics studies employed on plants,especially on non-model woody plants,under waterlogging with tab and salt water are relatively less.Taking the leaves of D.odorifera as experimental materials,this paper carried out widely-targeted metabolomics analysis based on ultra performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）.Results show that:543 kinds of metabolites were identified from all samples,most of which belong to organic acids and derivatives,flavonoid,amino acid and derivatives,lipids or phenylpropanoids.A total of 200 differentially accumulated metabolites（DAMs）were found in all stress treatments comoared with the control:113 in WM with 61 up-regulated and 52 down-regulated;86 in SM with 36 up-regulated and 50down-regulated;131 in SWM with 73 up-regulated and 58 down-regulated;31 common DAMs were found in stress treatments,among which flavonoids,such as persicoside,genistein（4’,5,7-trihydroxyisoflavone）,2’-hydroxygenistein and isorhamnetin 3-O-glucoside etc.,and phenylpropanoids and procyanidin A1 were significantly and steeply up-regulated,perhaps playing important roles in antioxidant defense and environmental adaptation.（2）metabolites were differentially accumulated in different treatments:phenylpropanoids and isoflavones were almost up-regulated in the stressed treatments;lipids were almost up-regulated in WM and SM,but down-regulated in SWM,suggesting that the responses of metabolites are treatment-specific and that biomaker could be selected for the specific treatment based on these work.Leaf metabolomics analyses were firstly performed in D.odorifera,therefore,these results could lay a foundation for the future research on the metabolites and metabolic pathways related to environmental stress,enriching the research area of plant metabolomics.