镉胁迫对尾巨桉幼苗生长和生理特性的影响

以尾巨桉(DH_32-29)幼苗为试验材料，以植株的生长指标(苗高、地径、叶面积)、生物量、根冠比、氮平衡指数(NBI)、叶绿素相对含量(SPAD 值)、丙二醛(MDA)含量和叶绿素荧光参数为指标，通过盆栽试验设置8个10~140 mg·kg^-1浓度镉(Cd)盐溶液处理，研究了不同浓度 Cd 胁迫处理下尾巨桉幼苗的形态和生理特性变化规律。结果显示：低浓度(10 mg·kg^-1)Cd 处理对尾巨桉幼苗的形态和生理特性无明显影响。当 Cd 浓度大于20 mg·kg^-1，随着 Cd浓度的逐渐增大，其对尾巨桉幼苗的伤害程度也逐渐增加，主要表现为：植株生长缓慢、生物量减小、叶绿素相对含量和叶绿素荧光参数(Fv/Fm、φPSⅡ、NP、NBI)均下降，qP 无明显变化， MDA 含量升高。Cd 浓度大于60 mg·kg^-1以上时，尾巨桉幼苗生长出现一定程度上的损伤症状和生长停滞现象。结果表明低浓度(≤20 mg·kg^-1)Cd处理下尾巨桉幼苗能正常生长，随着浓度的增大，Cd 处理对尾巨桉的形态和生理特性造成显著影响。同时结合部分桉树适生区土壤 Cd 含量调查及相关研究结果认为，尾巨桉具有一定修复 Cd 污染区土壤的潜力。

Morphological and Physiological Characteristics of Eucalyptus urophylla ×E. grandis (DH32-29) Seedlings Under Different Cadmium Concentrations

Cadmium is one of the most common heavy metals causing soil contamination problems. Bioremediation is an effective way to rehabilitate soils contaminated with this comp. An pot trial was conducted to measure various morphological and physiological indices of Eucalyptus urophylla × E. grandis (DH_32-29) grown under treatments of eight different soil concentrations of Cadmium (Cd) ranging from 10 to 140 mg·kg^-1. There were no significant differences found among seedling grown at low concentration (10 mg·kg^-1) of Cd and the control (i.e. no Cadmium). Under higher Cd concentrations (>20 mg·kg^-1) seedling growth was significantly impacted. As Cd concentration increases, the biomass, chlorophyll content, fluorescent parameter (PSⅡ), maximum photochemical quantum yield (Fv/Fm), efficiency of PS Ⅱ photochemistry (φPS Ⅱ ), non-photochemical quenching coefficient (Np) and nitrogen balance index (NBI) decreased, photochemical quenching (qP) showed little change, whilst malondialdehyde (MDA) increased. Seedlings of clone DH_32-29 show clear visible symptoms of injury at levels above 20 mg·kg^-1 and at plant growth stagnated at Cd concentration exceeding 40 mg·kg^-1. It was concluded that DH_32-29 seedlings can grow normally at lower Cadmium concentrations (≤20 mg·kg^-1). But as the concentration increases, above this level, the morphological and physiological characteristics of seedlings start to display significant impacts. Surveys of soil Cadmium levels in areas suited to Eucalyptus plantations and related research results in combination with this current study illustrate the potential soil remediation value of DH_32-29 for areas where soils are affected by Cd pollution.