The Research On Anatomical Traits And Phylogeny On Fine Roots Of 30 Lauraceae Plants

Functional traits of fine roots reflect the ecological adaptation strategy of plant roots in soil.Previous studies have shown that there were significant differences in fine root traits among tree species at large spatial and phylogenetic scales such as subtropical zones.However,the extent to which anatomical traits of related species are affected by phylogeny and the evolutionary adaptation strategies of fine roots remain to be further studied.In this study,30 Lauraceae species in subtropical zone were selected.The anatomical traits of firstorder roots(root diameter,cortical thickness,stele diameter and stele:root diameter ratio)were obtained through field sampling,cultivation and experimental measurement,aiming to illustrate the general variation of first-order anatomic traits of Lauraceae species at the species level.Blomberg’s K value was used to test the influence of phylogeny on anatomical traits and reveal the evolutionary adaptation strategies to the environment in Lauraceae.The study will help to provide evidences for further exploring the ecological synergistic function of root system in the process of evolutionary adaptation,and to further supplement the data of subtropical evergreen broad-leaved forest for the global fine root database.Specific conclusions are as follows:(1)There were significant interspecific differences in the four anatomical traits of firstorder roots of 30 Lauraceae species in homogenous as well as wild habitats.The interspecific coefficients of variation of fine root diameter,cortical thickness,stele diameter and stele:root diameter ratio were 34.12%,37.60%,41.41%and 25.74%,respectively.The variation of first-order root diameter in Lauraceae was mainly due to cortical thickness.(2)The four anatomical traits in Lauraceae all showed significant phylogenetic signals(p<0.001),but the Blomberg’s K value was small,indicating that anatomical traits were limited not only by phylogenetic history,but environmental factors.(3)The cortex thickness of Lauraceae was positively correlated with root diameter of first order(r=0.914,p<0.001),and the stele diameter was positively correlated with stele:root diameter(r=0.772,p<0.01).After phylogenetic independence comparisons,the correlation between these two pairs of traits remained unchanged.The synergistic effect of root anatomical traits reveals the evolutionary strategies for Lauraceae to adapt to environmental changes.(4)Lauraceae plants belong to thick-root strategy species.At the species level,the firstorder roots of Lauraceae species preferred to decreased root diameter in the process of evolution.At the global level,Lauraceae species were easy to be colonized by mycorrhizal fungi due to their thick roots,large cortex area and stele diameter,which is conducive to the absorption and transportation of water and nutrients.Therefore,the thick-root strategy is another advantage for Lauraceae species in humid subtropical forests.In conclusion,the first-order root anatomical traits of 30 common subtropical Lauraceae species showed significant interspecific differences and phylogenetic signals,which were determined not only by phylogeny,but also environmental factors.The coevolution of fine root anatomical traits and thick-root strategy is the key for Lauraceae to better adapt to environmental changes.