Synergistic response mechanisms in xylem and phloem of Artemisia ordosica to changes in precipitation
Aims Investigating the adaptive regulation of stem anatomy in desert plants under different precipitation scenarios will lead to a better understanding of the coordination mechanisms between water and carbon transport in desert plants under future precipitation patterns.Methods In this study,a two-factor completely randomized experiment was conducted to determine the axial and radial variation in the xylem and phloem anatomy of Artemisia ordosica stems under different precipitation conditions by manipulating precipitation in the field in a semi-arid climate zone,with three precipitation treatments in amounts(30％precipitation reduction,natural precipitation and 30％precipitation increase)and two precipitation intervals(5 d precipitation interval and 15 d precipitation interval).Important findings The results indicate:1)Under altered precipitation,A.ordosica did not develop more conductive axial xylem structures and more conductive axial phloem structures to adapt to the changes;2)Precipitation changes affected the radial anatomical traits of xylem and phloem of A.ordosica by altering the moisture content of the 40-60 cm soil layer.Under low moisture habitats,A.ordosica reduced the conduit diameter and increased the conduit wall thickness to ensure the safety of water transport,and maintained the phloem conductivity by increasing the lumen area of phloem sieve cells to ensure the effective transport of carbon,thus ensuring the normal physiological activities of A.ordosica;3)The xylem conduit and phloem lumen of A.ordosica had an equal scaling axial scaling pattern,and the two were synergistically related to each other to maintain the hydraulic function,and this correlation was not affected by changes in precipitation.This study showed that A.ordosica adapted to changes in precipitation by altering the radial stem structure rather than the axial.This study is a valuable addition to the anatomical knowledge of the hydraulic structure of desert shrubs and provides a theoretical basis for future management of vegetation stability maintenance under changing precipitation patterns in semi-arid desert areas.
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