3种土壤类型下镉胁迫对红椿生物量分配及其镉富集特性的影响

摘要

红椿(Toona ciliata Roem.)为中国国家级(Ⅱ)重点保护植物,同时也是(亚)热带珍贵速生用材树种.为了解镉(Cd)胁迫对红椿生长及镉富集特性的影响,采用盆栽控制试验研究了长江上游3种典型土壤(黄壤、酸性紫色土和冲积土)条件下,不同浓度Cd处理[0(对照)、20、40、80和160 mg·kg-1]对其幼树生长发育、生物量分配、镉积累与分配及镉富集特性的影响,为深入认识镉污染土壤的有效修复提供理论依据.结果显示,(1)低浓度镉胁迫(<40 mg·kg-1)可促进红椿幼树生长,而高浓度镉胁迫(≥40 mg·kg-1)则表现为严重抑制;各器官生物量随镉浓度增加而先升后降,除酸性紫色土壤上茎生物量外.(2)3种土壤条件下,红椿幼树各器官镉含量均随镉处理浓度增大而增大.相同镉浓度处理下主根镉含量表现为:黄壤>酸性紫色土≥冲积土,而冲积土条件下侧根镉含量均低于黄壤或酸性紫色土.同时,3种土壤下各器官镉含量随土壤镉浓度增大而增加,且地下部显著大于地上部.(3)随着镉处理浓度增大,除地上部富集系数(BC)在冲积土条件下无显著差异外,其他土壤条件下地上和地下部均显著增大;而3种土壤条件下转移系数(TF)均逐渐降低.高浓度镉胁迫下,幼树BC和TF虽均大于1,但地上部镉含量低于100 mg·kg-1.随着镉浓度升高,3种土壤条件下红椿耐性指数(TI)均先增后降,高镉处理下冲积土TI显著大于黄壤和酸性紫色土壤.红椿虽不是典型的镉超富集植物,但其能在较严重镉污染土壤中较好生存,可作为镉污染区域(特别是镉污染冲击土)潜在的土壤修复树种.%Toona ciliata Roem. is a vital and precious fast-growing species in tropical and subtropical regions due to the national class Ⅱ key protected plants. The presented work investigated the effects of different cadmium (Cd) stress on the growth and Cd accumulation characteristics of T. ciliata seedlings under three types of soil (yellow soil, acid purple soil and alluvial soil) in the middle and lower reaches of the Yangtze River, which will provide a theoretical basis for the effective restoration of Cd contaminated soil. A controlled pot-experiment was arranged with different treatments of five Cd dosages [0 (control), 20, 40, 80 and 160 mg·kg-1] to investigate the growth characteristics, accumulation and distribution of biomass and Cd, and Cd enrichment in the T. ciliata seedlings. The results indicated that: (1) low concentration of Cd stress (<40 mg·kg-1) promoted the growth of T. ciliata seedlings, while the high concentration of Cd stress (≥40 mg·kg-1) seriously inhibited its growth. In addition, the biomass of each organ was increased first and then decreased with the increase of Cd concentration, but for the decrease of stem biomass in acid purple soil. (2) Under three different soil conditions, the contents of Cd in the organs of the seedlings were increased with the increase of Cd concentration. In detail, the content of Cd in lateral root was the highest, followed by leaf, and the content of main root and stem was the lowest. Under the same dose of Cd treatment, the main root Cd content was yellow soil>acid purple soil≥alluvial soil, while the contents of root Cd were lower in alluvial soil than that in yellow soil or acidic purple soil. The Cd content of the organs in the three soils increased significantly with the increase of the soil Cd concentration, and the root Cd content was significantly higher than that of the shoots. (3) With the increase of Cd dose applied, there was no significant difference in the bioaccumulation Coefficient (BC) under alluvial soil conditions, while the BC of shoot and root increased significantly. However, the translocation factor (TF) decreased gradually with the increase of Cd dose applied under three soil conditions. Moreover, under the high dose of Cd stress, the BC and TF were higher than 1, but the Cd content in the shoot was less than 100 mg·kg-1. Additionally, with the increase of Cd dose, the tolerance index (TI) was increased firstly and then decreased under the three soil conditions, and the TI in the alluvial soil was significantly higher than that in the yellow soil and/or the acidic purple soil under higher Cd treatments. These results indicate that T. ciliate could have a good growth in the soils with severe Cd pollution even through it is not a typical cadmium hyperaccumulator plants, which could be a potential tree species for Cd phytoremediation in Cd contaminated areas, especially in alluvial soil with Cd pollution.