秋华柳和枫杨幼苗对镉的积累和耐受性

以秋华柳和枫杨当年实生幼苗为研究对象,采用向土壤添加外源镉(CdCl₂ · 2.5H₂O)的形式设置了0(对照组)、10 、20 、50、100 mg/kg 5个处理,研究了镉胁迫下秋华柳和枫杨幼苗的生长、生物量变化和根茎叶镉含量,并评价了两树种的耐性指数(Ti)、转移系数(Tf)和生物富集系数(BCF)。结果表明:(1)在镉含量为10 mg/kg时,秋华柳和枫杨幼苗基于生长和生物量参数的耐性指数(Ti)分别为91.72和91.62,与对照组相比无显著变化,其余各组(20、50、100 mg/kg)则显著低于对照植株(P<0.05);(2) 土壤镉浓度小于20mg/kg时,秋华柳植株茎、叶镉积累量分别高达61.73 mg/kg、163.04 mg/kg,根镉积累量为91.05 mg/kg;枫杨植株茎、叶镉积累量最高分别为7.9 mg/kg、5.25 mg/kg,仅为秋华柳茎、叶的12.8%和3.2%,根镉积累量高达190.68 mg/kg;(3) 除对照外,秋华柳幼苗各部分镉含量为叶＞根＞茎,转移系数(Tf)介于0.789-1.513之间,枫杨幼苗各部分镉含量为根＞茎＞叶,转移系数(Tf)介于0.037-0.044之间,远远小于秋华柳Tf;(4)秋华柳和枫杨幼苗在土壤镉浓度为10 mg/kg时具有很高的生长适应性和耐性,秋华柳根吸收的镉向地上部分转移能力、地上部分积累镉的能力都远远大于枫杨,生物富集系数(BCF)进一步证实了这一特性。研究证明,秋华柳植株具有很高的镉耐性、镉转移能力及地上部分积累镉的能力,适合于镉污染严重区域的植物修复。

Accumulation and tolerance of Salix variegate and Pterocarya stenoptera seedlings to cadmium

Cadmium (Cd) is the most popular heavy metal element in the contaminated soil of Three Gorges Reservoir Region. Cadmium has significant negative effects on the health of soil-plant system in the research area due to its high concentration and biological activity. Thus, it is essential to study the tolerance and accumulative ability of plant species in cadmium contaminated soils in order to protect the ecological environment and plan the reasonable land use. Salix variegate and Pterocarya stenoptera are two native riparian plants which can be used widely in the vegetation restoration of the hydro-fluctuation zone in Three Gorges Reservoir Region. In order to reveal the response of these two species to cadmium, five different kinds of cadmium treatment were applied to determine the growth, biomass and cadmium concentration in various parts of S. variegate and P. stenoptera seedlings. The cadmium treatments were 0(control), 10, 20, 50, and 100 mg/kg. The results showed that: (1) The root biomass, aerial biomass, changes of stem length and stem diameter of S. variegate and P. stenoptera seedlings decreased with Cd content raised. Tolerance index (Ti) based on the dry biomass and growth parameters of two species showed no significant difference in 10 mg/kg in contrast with a significant decrease in 20, 50, and 100 mg/kg (P<0.05), when compared to the control respectively. (2) The cadmium concentration reached up to 61.73, 163.04, and 91.05 mg/kg in stems, leaves, and roots of S. variegate in turn when treated with cadmium less than 20 mg/kg. However, in the same treated condition, the highest cadmium concentration was 7.9, 5.25, and 190.68 mg/kg in stems, leaves, and roots of P. stenoptera, respectively. (3) Cd accumulation in S. variegate was highest in leaves and lowest in stems except in the control, with the translocation factor (Tf) between 0.789 1.513. Very differently, Cd accumulation in P. stenoptera was highest in roots and lowest in stems also except in the control, with the translocation factor (Tf) between 0.037 0.044. Thus, the translocation factor (Tf) of P. stenoptera was far less than that of S. variegate. These characteristics indicated strategies of cadmium uptake and translocation by two plant species growing in Cd-contaminated soil were not totally different: Cd tended to be immobilised and held primarily in the roots of P. stenoptera, whereas it was more easily translocated to the aerial tissues of S. variegate. The tolerance of species to cadmium was demonstrated by these two strategies so that the plants were able to survive and had a high productivity. (4)The results indicated that S. variegate and P. stenoptera seedlings had a high capacity of growth adaptation and tolerance under 10 mg/kg Cd stress, and also, the capacities of translocation and cadmium accumulation in aerial parts of S. variegate seedlings were higher than that of P. stenoptera seedlings, which verified that the differences in accumulation of cadmium were not correlated with tolerance ability of plants. Such a behavior in the seedlings of two species was further confirmed by the calculation of the bio-concentration factor (BCF). The study suggested that S. variegate had considerable potential application to those cadmium contaminated areas in the hydro-fluctuation zone of the Three Gorges Reservoir Region.