异质性重金属镉胁迫下克隆整合对匍匐茎草本植物积雪草生长的影响

 采用盆栽试验研究了异质性重金属镉胁迫下, 克隆整合对匍匐茎草本植物积雪草(Centella asiatica)生长的影响。将远端分株(相对年幼的分株)分别置于对照和镉胁迫处理下, 并对远端分株与近端分株(相对年长的分株)之间的匍匐茎进行切断或保持连接处理。研究结果显示: 镉胁迫处理显著降低了积雪草远端分株的净光合速率(P_n)、最大光量子产量(F_v/F_m)、叶绿素含量、叶面积、分株数和生物量; 克隆整合缓解了镉胁迫对远端分株生长的不利影响; 克隆整合不仅未导致相连近端分株的损耗, 而且相连近端分株的光合效率也没有表现出补偿性增加; 克隆整合降低了远端受胁迫分株的根冠比, 从而使之减少了对土壤中重金属镉的吸收; 匍匐茎切断和镉胁迫处理对近端分株、远端分株的叶柄长没有显著的影响。结果表明: 克隆整合提高了积雪草遭受镉胁迫的远端分株的生长, 改变了其生物量分配格局, 并有助于整个克隆片段在异质性重金属胁迫下的生长。该研究对于丰富和发展异质性环境胁迫下克隆整合的生态适应对策具有重要意义。

Effects of clonal integration on growth of stoloniferous herb Centella asiatica suffering from heterogeneous heavy metal Cd~(2+) stress

Aims A pot experiment to examine the effects of clonal integration on growth of the stoloniferous herb Centella asiatica suffering from heterogeneous heavy metal Cd²⁺ stress was conducted to address two questions: (1) does clonal integration alleviate the negative effects on growth of clonal plants suffering from heterogeneous heavy metal stress; and (2) do the ramets growing in unfavorable microhabitats incur increased photosynthetic efficiency in the connected ramets?
Methods Relatively young, distal ramets of C. asiatica were assigned to normal or Cd²⁺ stressed soil, and the stolon connections between the relatively old proximal ramets and the young distal ramets were either severed or left intact. The net photosynthetic rate (P_n), chlorophyll fluorescence (maximum quantum yield of PSII, F_v/F_m) and chlorophyll contents of distal ramets and P_n of proximal ramets were measured. The growth performance of distal and proximal ramets was investigated at the end of the experiment.
Important findings Cd²⁺ stress treatment significantly decreased the P_n, F_v/F_m, chlorophyll contents and growth of distal ramets. Clonal integration significantly alleviated the negative effect of Cd²⁺ stress to distal ramets in terms of P_n, F_v/F_m, chlorophyll contents and biomass of distal ramets. There was no significant cost to the connected proximal ramets, and clonal integration did not incur increased photosynthetic efficiency in the proximal ramets. In addition, clonal integration significantly decreased root to shoot ratio of distal ramets suffering from Cd²⁺ stress, and reduced the uptake of the heavy metal. Petiole length of proximal and distal ramets was not significantly affected by stolon severing and Cd²⁺ stress. It is suggested that clonal integration may
enhance growth of clonal plants suffering from heterogeneous heavy metal stress.