| Under the background of drought and climate warming,how to ensure the safety and effectiveness of water transport in plants has always been a hot and difficult research topic.The storage capacity and mechanical strength of branches of woody plants are closely related to the embolism resistance and water transport safety of xylem ducts of branches.To study the relationship between storage capacity and mechanical strength of branches and xylem anatomical characteristics of branches is helpful to understand the resistance strategies of different tree species under different stress conditions,and to predict the evolution direction of forest communities in Taishan Mountains.It provides the theoretical basis for screening the dominant afforestation species.Based on this,this study selected 9 tree species(Castanea mollissima、Diospyros kaki、Juglans regia、Pinus tabuliformis、Platycladus orientalis、Quercus acutissima、Robinia pseudoacacia、Styphnolobium japonicum、Yulania denudata)in Taishan Mountain as the research object.By measuring the content of NSC in xylem of branches,the proportion of thin-wall tissue and its components,and the mechanical strength related characteristics such as thick-span ratio,wood density,fiber tissue,etc.Potential maximum water conductivity,vessel hydraulic diameter,vessel density and other relevant characteristics of water transport,explore the relationship between the xylem anatomical characteristics of branches of different tree species,storage capacity and mechanical strength,and analyze the proportion tradeoff of xylem anatomical components.The results show that:(1)The contents of NSC and its components in 9 tree species were positively correlated with the proportion of parenchyma,especially the proportion of axial parenchyma,indicating that parenchyma is the main storage site of non-structural carbohydrates in plants.The proportion of detached parenchyma tissue(13.22±1.56%),the proportion of axial parenchyma tissue(21.86±1.99%)and the proportion of total parenchyma tissue(60.25±5.95%)were all the maximum values of the nine species,indicating that Quercus acutissima had the potential of maximum storage capacity.(2)The wood density of circumferential wood species was significantly higher than that of non-perforated wood and non-perforated wood.The thickness-span ratio of Styphnolobium japonicum was 92.95±22.93%,which was the maximum of the nine trees,indicating that the mechanical strength of xylem of branches might be related to the arrangement of conduits.(3)There is a trade-off between the efficiency and safety of water transport in the catheter.The efficiency of water transport is mainly related to the proportion of the catheter,while the safety is mainly related to the wall thickness of the catheter,the index of the catheter group and the connection degree of the catheter.(4)The proportion tradeoff of xylem components mainly existed between fibrous tissue and parenchyma tissue.In addition,the proportion tradeoff of xylem components of hardwood species was also related to the proportion of ducts.(5)Among the 9 tree species selected in this paper,Quercus acutisa has clustered catheters of both size and diameter,larger proportion of thin-walled tissue,catheter density,catheter connection and independent catheter index,and low-ray structure.Its mechanical strength and storage capacity are also relatively good,indicating that its xylem physiological structure is beneficial to better adapt to environmental changes.It is more likely to become the dominant tree species in the succession process of Taishan Mountains in the future.The comprehensive evaluation of drought resistance of 9 tree species was as follows: Quercus acutissima > Yulania denudata > Styphnolobium japonicum > Juglans regia > Castanea mollissima > Diospyros kaki > Robinia pseudoacacia > Pinus tabuliformis > Platycladus orientalis. |
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