施氮对干旱胁迫下毛竹幼苗生物量和根系形态的影响

Effects of nitrogen addition on biomass and root morphology of Phyllostachys edulis seedlings under drought stress

为探讨氮素添加对水分胁迫下毛竹幼苗地上生物量及地下根系形态的调控作用,选取1年生毛竹实生苗为材料,采用水分和施氮双因素完全随机区组设计,以田间持水量的80%~85%作为水分对照(CK)、50%~55%为中度干旱(MD)、30%~35%为重度干旱(HD)设置3个水分水平,氮处理分未施氮(N0,0 mg N·kg^(-1))和施氮(N1,100 mg N·kg^(-1))2个水平,通过盆栽试验,测定毛竹实生苗根系形态特征及各器官生物量。结果显示:施氮显著增加了同一水分下毛竹幼苗叶、根及整株生物量,其中,N1MD和N1HD分别较N0MD和N0HD地上生物量增加15.6%、11.9%,总生物量分别增加36.7%、25.0%(P<0.05);施氮降低了相同水分处理下毛竹的比根长、茎叶比,显著促进了中度和重度干旱下根冠比的增加(P<0.05);水分胁迫下,除根生物量比显著增加外,茎、叶生物量比均随氮素添加呈减小的趋势;施氮对毛竹幼苗根系形态特征(根长、根表面积、根体积)具有不同程度的促进作用;施氮对中度干旱下毛竹幼苗干物质积累的缓解作用比重度干旱大,但在毛竹根系形态中,施氮对于重度干旱的作用效果更强。研究表明,施氮促使干旱胁迫下毛竹调整自身物质分配以优化对有限资源的获取,也有助于干旱胁迫下毛竹根系形态的塑造,在一定程度上缓解了干旱胁迫对毛竹幼苗生长的抑制作用。

We investigated the responses of aboveground biomass and root morphological characteristics of Phyllostachys edulis seedlings to nitrogen addition under different levels of drought stress.The experiment followed a two-factor completely random block design,with three levels of soil water condition(CK,MD,and HD with 80%-85%,50%-55%,and 30%-35%of field water-holding capacity,respectively)and two levels of nitrogen addition(N0,0 mg N·kg^(-1);N1,100 mg N·kg^(-1)).The root morphological characteristics and biomass of seedlings were measured.The results showed that nitrogen addition increased the biomass of leaf and root in Ph.edulis seedlings under the same water level.Compared with N0 MD and N0 HD,the aboveground biomass of N1 MD and N1 HD increased by 15.6%and 11.9%,while the total biomass increased by 36.7%and 25.0%,respectively(P<0.05).Nitrogen addition reduced the specific root length and stem/leaf ratio of Ph.edulis seedlings under the same water level,but significantly promoted root/shoot ratio under moderate and high drought stresses(P<0.05).Under water stress,the proportion of root biomass increased significantly,while the proportion of stem and leaf biomass showed a decreasing trend with nitrogen addition.Nitrogen addition improved root morphological characteristics(root length,root surface area,root volume)of Ph.edulis.Nitrogen addition showed stronger enhancement on dry matter accumulation of Ph.edulis seedlings under moderate drought than under high drought stress,while better alleviated the stress of high drought on root morphology.In conclusion,nitrogen application prompted Ph.edulis to adjust its biomass allocation under drought stress to optimize the access to limited resources.It also facilitates to shape root morphological characteristics through alleviating the inhibitory effect of drought on the growth of Ph.edulis seedlings.