胡杨幼苗根系生长与构型对土壤水分的响应

Response of Root Growth and Architecture of Populus euphratica Seedling on Soil Water

胡杨实生幼苗成活率低是制约其更新与人工育苗保存的关键问题,而幼苗根系生长与构型是影响其存活的重要因素。该试验以1年生胡杨幼苗为材料,通过2种给水方式(断续给水和连续给水)下各6个土壤水分梯度处理的控制试验,探究胡杨幼苗根系生长与构型对荒漠地区关键因子水分的响应特征。结果表明:(1)2种给水方式下干旱胁迫均使根冠比增加,且断续给水处理下幼苗根冠比显著大于连续给水。(2)一定程度的干旱处理还可以促进幼苗根系形态发育特征的发展和根系生物量的积累,但过度干旱胁迫或土壤水分含量过多都会抑制根系生长,并以连续给水、土壤含水量15%处理下幼苗根系最为发达。(3)幼苗深扎根能力强,其根宽深比在2种给水方式下均小于1,且断续给水处理显著小于连续给水处理;2种给水方式下根宽深比都与土壤水分含量呈显著正相关。(4)根系拓扑指数在2种给水方式下无显著差异且均接近1,但都与土壤水分含量呈显著负相关。即幼苗根系趋向鱼尾状分支结构,次级分支少,这种根系延伸策略有利于胡杨幼苗在干旱贫瘠的土壤环境中生存。(5)根系构型参数的主成分分析显示,总根长、总根表面积、根宽深比和拓扑指数在2种给水方式下都能很好地表示胡杨幼苗根系构型特征。可见,胡杨幼苗根系通过构筑鱼尾状分支结构、增加垂直根纵向延伸能力和增大根冠比适应干旱环境;水分对于胡杨幼苗根系生长与构型作用显著,根系对水分因子的响应对于胡杨幼苗适应水分异质性环境具有重要意义。

By setting up the controlled-experiment with soil water content,we analyzed the root growth and architecture of Populus euphratica seedling to indicate the relationship between the root development and soil water content.The results showed that：（1）drought stress caused the increase of root to shoot ratio to adapt to the arid environment.（2）A certain degree of drought treatment promoted the development of root morphological characteristics and biomass.But excessive drought stress or soil water content may inhibit root growth.Root was most developed under the 15% water content with continuous water treatments.（3）Ration of width to depth of seedling＇s root system was less than 1with both water treatment,the root have a high ability to grow deeper.The ration under intermittent water treatment was significantly less than those under continuous water treatment.There is a significant positive correlation with water content for both water treatments.（4）Topological index of both water treatment was close to 1and the root branching patterns were herringbone-like,root branching ability was week.The root extension strategy was helpful for the seedling to survive in dry and infertile soil environment.The index was significantly negatively cor-related with the water content for both water treatments.（5）A total of 10 parameters of root architecture were analyzed by the principal component analysis.The parameters of total root length,total root surface area,ration of width to depth and topological index could well present the root architecture characteristics of P.euphraticaseedling＇s root with both water treatments.We concluded that P.euphraticaseedling adapt to the arid environment through the establishment of herringbone-like branching patterns,increase of the vertical longitudinal extension ability and root to shoot ratio.Soil water factor played an important role in regulating P.euphraticaseedling＇s root growth and architecture.The ability to response to soil water content of P.euphraticaseedling＇s root system may lead to the success to adapt to heterogeneity in soil water.