Anatomical Characteristics In Roots Of Perennial Forbs In The Loess Plateau,China

Plant stem xylem system of woody species has an important role in long-distance water transport,and the scientific description of anatomical xylem structure and functions are essential for understanding the transportation mechanism and allocation strategies of water and nutrient of woody species.However,the related research on perennial herbaceous species has received scant attention.In this study,the main root samples of 30 perennial herbaceous along the precipitation gradient(from 250 mm to 530 mm)in the Loess Plateau were collected.We measured eight hydraulic conductivity traits and analyzed their spatial variability.The results indicated that:1)the value of xylem traits had comparatively large magnitude of variability.The number of vessel,vessel fraction,mean vessel diameter and total water transfer efficiency ranged from 25 to 295,24.46 ?n to 54.58?m,2.42%to 33.16%,and 0.034 kg·m-1.Mpa-l·s-1 to 25.357 kg·m-1·Mpa-1·s-1,respectively;2)The vessel diameter,vessel fraction and water transfer efficiency of xylem conduits roughly kept steady decreasing trend with the increasing precipitation.In particular,the negative relationship between water transfer efficiency and precipitation approached the significant levels(r=-0.3?-0.362,P<0.05).This emphasized the fact that moisture availability exerted significant influence on spatial variability of hydraulic conduct traits of the perennial herbaceous species in the Loess Plateau;3)The value of vessel diameter and water transfer efficiency were the highest of the herbaceous species in the family of Zygophyllaceae that mainly distributed in sub-desert regions,followed by the herbaceous species(planted species)of Leguminosae family,and the lowest value were found in the herbaceous species(native species)of Compositae family,indicating the heterogeneous hydraulic traits and diverse water transfer strategies of different phyto-groups of perennial herbaceous species on the Loess Plateau.During the early and late growing seasons,the water-carrying capacity of artificially cultivated Medicago saliva changed greatly,and at the same time,the water demand capacity was large in the early growing season,but gradually decreased in the late growing season.Compared with artificially cultivated species,the number of vessels(83.08%)and total vessel area(86.36%)of naturally distributed Potentilla chinensis throughout the growing season are much larger than those of Medicago sativa.The climate response has a strong consistency.In terms of precipitation gradient and temperature gradient,artificially cultivated Medicago sativa has a more stable change trend than naturally distributed Potentilla chinensis.This result laid the foundation for understanding the differences between the water-convesseling characteristics of artificially cultivated species and natural wild species,as well as the use of artificially cultivated perennial herbaceous plants to solve the problem of soil erosion in arid loess areas.