The Study Of Physiological Response Mechanism And Metabolomics On Belamcanda Chinensis L. Under Drought

Drought has become an increasingly important environmental problem and one of the major non-biological stress factors affecting the growth and development of crops.It is of great significance to elucidate the mechanism of plant drought resistance for improving plant drought resistance ability and breeding drought-resistant varieties.Belamcanda chinensis L.as a perennial herb belonging to the genus Irisidae is an important medicinal plant and garden plant in China.Its rhizome plays an important role in antioxidant,anti-inflammatory and anti-tumor,etc.In addition,because of its drought resistance,B.chinensis is widely used in greening parks and scenic spots.In this study,to reveal the defensive responsing mechanism of B.chinensis under drought,the physiological and biochemical response mechanism of B.chinensis seedlings under drought at 0 d,7 d,14 d,21 d,28 d and after rehydration was studied by pot water control method.The metabolomics of B.chinensis root system was also analyzed by liquid chromatography-mass spectrometry（LC-MS）.The main results are as follows:1.With the extension of drought stress time,the relative water content of plants decreased gradually,while plant height,leaf number and leaf area increased gradually slowly.Meanwhile,total root length,total surface area,volume,average ground diameter and specific root length all increased gradually,the root shoot ratio increased first and then decreased,the root activity decreased gradually,the root structure was damaged,and the cortex was irregular and cracked.Root anatomic radius,middle column diameter,cortical thickness and catheter diameter all increased first and then decreased.The root anatomic parameters recovered after rehydration.2.Drought leading to the loss of aboveground water,blocked chlorophyll synthesis and decreased chlorophyll content.Pn,Gs and Tr decreased,while Ci increased.The F₀,q N,NPQ increased,while the Fm,q P and Fv/Fm decreased.After 28 days of drought,the difference was significant（P<0.05）,and the chlorophyll content,photosynthetic parameters and chlorophyll fluorescence parameters were recovered after rehydration,which proved that B.chinensis had certain adaptability to drought resistance.3.With the extension of drought stress time,the function of cell membrane was damaged,the relative conductivity and malondialdehyde content of roots and leaves showed an increasing trend,and the contents of soluble protein,free proline and other osmotic regulating substances in roots also accumulated in large quantities.Meanwhile,the contents of H₂O₂and O₂^·-were gradually increased,and DAB and NBT staining were gradually deepened.After rehydration,all indexes recovered to a certain extent.At the same time,the activities of POD,CAT,GR,APX and MDHAR in roots and leaves and SOD in leaves reached the maximum value at 28 days of drought,and all of them recovered to different degrees after rehydration.4.Under drought,a total of 656 different metabolites were screened from the roots of the stem.KEGG annotation analysis revealed that the key metabolic pathways were glycerolipid metabolism,sphingolipid metabolism,amino acid metabolism,tyrosine metabolism,arachidonic acid metabolism,flavonoid and flavonol biosynthesis,steroid biosynthesis and tyrosine metabolism.The biosynthesis of flavonoids varied greatly,which indicated that flavonoids played an important role in drought response.5.Through weighted gene co-expression network analysis（WGCNA）,it was found that the three metabolite modules were highly correlated with root growth parameters and physiological and biochemical parameters.Among them,Meblue module was positively correlated with root activity.Megreen module is positively correlated with catalase.The Meturquoise module is positively correlated with malondialdehyde,catalase,soluble protein and relative conductivity.