基于根系形态可塑性的空心莲子草克隆分工特征

Division of labor in Alternanthera philoxeroides based root morphological plasticity

关键词:  空心莲子草  异质性斑块  克隆分工  根系  形态可塑性

Key words:  Alternanthera philoxeroides  heterogeneous patch  the division of labor  root  morphological plasticity

摘要:

资源在空间和时间上不均匀分布现象往往形成资源异质性斑块,克隆植物凭借强大的侧向生长能力占据广阔空间,分株间的生理连接促进了其对异质性生境的适应。克隆分株首先通过资源获取结构的功能特化来提高从各种资源富养斑块中的养分获取,然后通过克隆整合作用实现分株间的养分传输,这种功能特化和资源共享模式被称为‘分工'。该文以入侵克隆植物空心莲子草(Alternanthera philoxeroides)为研究对象,研究其根系对资源异质性分布的形态可塑性响应; 通过调节光照强度和土壤养分来实现资源的异质性分布,共设置4个处理:①近端分株高光低养—远端分株高光低养(HL-HL),②近端分株低光高养—远端分株低光高养(LH-LH),③近端分株高光低养—远端分株低光高养(HL-LH),④近端分株低光高养—远端分株高光低养(LH-HL); 使用WinRHIZO Pro软件分析相关根系指标,SPSS 18.0单因素方差(one-way ANOVA)分析方法分析异质性条件对近、远端分株以及整个克隆片段的影响。结果表明:异质性斑块中经历高光低养的分株分配更多的生物量到地上部分,经历低光高养的分株分配更多的生物量到地下部分,空心莲子草通过调整对地上和地下部分的生物量分配比例实现了克隆分工; 异质性斑块中,生长在富养斑块中的空心莲子草分株根系有更高的根生物量、根长、根表面积、根体积以及分枝系数等,表明空心莲子草分株根系通过对异质性斑块的形态可塑性变化提高了土壤养分的吸收能力。由此可见,空心莲子草通过对资源获取结构的功能特化提高了其资源吸收能力,这可能是其具强入侵能力的重要原因。

Abstract:

The distribution of resources is uneven over space and time, which always leads to heterogeneous patches. Clonal plants usually occupy wider habitats because of powerful clonal growth and the physical connection between ramets promotes the adaptation to heterogeneous habitats. Clonal ramets can improve resource capture capacity in nutrient-rich patches by the functional specializing of resource acquisition organs, then share these resources with the ramets in low nutrient patches through clonal integration, this pattern is called ‘division of labor'. Our study selected Alternanthera philoxeroides, an invasive clonal weed, as the objective and studied on the morphological plasticity of roots in the heterogeneous patches of resources. Ramets were planted in the patches with heterogeneous distribution of light and soil nutrient and there were four treatments, e.g. ①two ramets experienced high light and low nutrient treatment(HL-HL); ②two ramets experienced low light intensity and high nutrient treatment(LH-LH); ③proximal ramets experienced high light and low nutrient treatment, distal ramets experienced low light and high nutrient treatment(HL-LH); ④proximal ramets experienced low light and high nutrient treatment, distal ramets experienced high light low nutrient treatment(LH-HL). Parameters of roots were analyzed with WinRHIZO Pro software and the effect of treatment on these parameters of proximal ramets, distal ramets and whole ramet pairs was tested with one-way ANOVA(SPSS 18.0). Our results were as follows: Ramets in high light and low nutrient patch allocated more biomass to aboveground parts, while ramets experienced low light and high nutrient allocated more biomass to the underground parts. A. philoxeroides ramets showed the division of labor by changing the root-shoot ratio of biomass. In heterogeneous environments, the root of A. philoxeroides ramets in the eutrophic patches had higher root biomass, root length, root surface area, root volume and branch coefficient, etc. A. philoxeroides increased nutrient uptake capacity through the form of root morphological plasticity in heterogeneity habitats. Thus, A. philoxeroides improved resource absorption capacity by specializing resource acquisition organs, which may play an important role in its successful invasion.