The Relationship Between Xylem Embolism And Embolism Recovery And Plant Drought Resistance In Seven Genus Acer

The xylem embolism caused by drought stress affects the normal water transport function of plants,which is the key factor that restricts the growth and development of plants and affects their distribution.It has been widely concerned and studied.Numerous studies have shown that the drought resistance of plants is affected by embolism and embolism recovery.The study of embolism and its recovery are helpful to understand the regulation mechanism of plant water transport to explore drought response of plants,and to improve the short-term of plant in production practice.It is conducive to improving plant productivity in production practice,and is of great theoretical and practical significance for optimizing plant water use efficiency.Seven genus Acer(Acer buergerianum,Acer palmatum,Acer negundo,Acer ginnala,Acer platanoides,Acer truncatum,Acer mono)were selected for this study as Acer are wildly studied in the field of embolism resistance,which have the high resistance ability and is easy to be planted in the northwest region,and their shape are beautiful and has ornamental value.The embolism vulnerability curve was fitted by the centrifuge method and the twodimensional Boolean function,and the embolism vulnerability of the selected genus Acer were studied.The rehydration rate was meaured by method of low pressure liquid flow meter(LPFM)and the xylem anatomical structure.The anatomical structure of the xylem was observed by staining and microscopy and the parameters of the catheter were recorded.This study has shown that:1.Seven genus Acer can achieve their own drought resistance by regulating embolism characteristics: The genus Acer which embolism vulnerability curve is "s"-shape can increase their drought resistance by increasing embolism resistance,and The genus Acer which embolism vulnerability curve is "r"-shape can increase their drought resistance by increasing embolism vulnerability.The two-component curve Acer have higher drought resistance and the adjustment mechanism is more flexible and intelligent.Under mild drought stress,water consumption is reduced by active embolization,and under severe drought stress,plant drought resistance is improved by increasing embolism resistance.2.The xylem embolism recovery is one of the mechanisms of drought resistance of the genus Acer.When the water potential increases,the xylem embolism can quickly restore the water.The degree of embolism recovery of seven genus Acer are directly proportional to the rehydration time.The rehydration rate measured by hydralics and by the characteristic values of xylem conduit have some differences.3.Combining the anatomical structure of the xylem,the intuitive and in-depth analysis of the specific rules and mechanisms of embolism and embolism recovery is beneficial to the drought resistance of plants.(1)The anatomical structure of the xylem is closely related to its embolism vulnerability.By reducing the length of the conduit,increasing the inner diameter and the thickness of the tube wall,the degree of conduit connection is increased and the conduit is sparsely distributed,so that the embolism resistance performance of the "s"-shaped curve Acer are stronger,and the embolism vulnerability of "r"-shaped curve Acer species are stronger to form embolism and improve the drought resistance of plants.The two-component rule of the curve of Acer buergerianum and Acer platanoides caused a part of conduit to lose water quickly to form embolism,while the other part has a stronger embolism resistance ability.(2)The relationship between the anatomical structure of the xylem and the embolism recovery ability is as follows: The embolism recovery measured by LPFM found that the tree species with the characteristics of thick and short conduit,high degree of joint between the ducts and small duct density had strong embolic recovery ability.However,the embolism recovery measured by staining method has reached different conclusions,which is tree with slender tube,high degree of inter-catheter connection and high duct density has strong embolism recovery ability.The embolism recovery has a more complex internal mechanism and needs further study.(3)This study found that the embolism recovery of xylem began at both ends of the stem and then gradually extended to the middle of the stem.It is shown that in addition to the traditional embolism recovery mode by radial recovery of the xylem conduuit pit membrane,there is a new mode of embolism recovery along the axial direction of the xylem conduit.The study also confirmed Brodersen's hypothesis that in a specific structure in which multiple conduits are arranged side by side,a thin conduit with strong anti-embolism ability acts as an important "reservoir" and provides rehydration conditions for the thick conduits that is easy to embolism.This process serves to promote embolism recovery.In summary,the different xylem structural features of different species of Acer have different embedding characteristics and embolism recovery ability,thus showing different degrees of plant drought resistance and achieving drought stress response.