Abstract:

In order to explore the sensitivity differences of shrub seedlings and different test endpoints to cadmium （Cd） poisoning， 12 common shrubs were selected for hydroponic experiment of Cd toxicity to shrub seedlings， and the seedlings growth parameters （apparent toxicity symptoms， plant height， fresh and dry weight of shoots， root growth state） under different concentrations of Cd treatments ［0（CK）， 0.5， 1.0， 2.0， 4.0， 8.0， 16.0， 32.0 mg·L^-1］ were determined to compare the stability of different test endpoints. Meanwhile， the species sensitivity distributions （SSD） were made using the Burr-Ⅲ model to analyze the sensitivity of different shrub seedlings to Cd. All the studied plant seedlings showed toxicity symptoms in Cd concentrations ranges of 1.0~4.0 mg·L^-1. The discrapency of Cd toxicity thresholds on different toxic endpoint of plant shoots and roots growth was large. Toxicity thresholds corresponding to 10% （EC₁₀） and 50% （EC₅₀） inhibition of shoot dry weight values ranged from 0.11 （Pittosporum tobira） to 1.30 mg·L^-1 （Fatsia japonica） and 2.58 （Ligustrum japonicum ‘Howardii’） to 10.90 mg·L^-1 （Fatsia japonica）， and the difference multiple reached 11.8 and 4.2 times， respectively. The EC₁₀ and EC₅₀ values of root branch number ranged from 0.08 （Ligustrum japonicum ‘Howardii’） to 1.27 mg·L^-1 （Fatsia japonica） and 2.40 （Ligustrum japonicum ‘Howardii’） to 10.30 mg·L^-1 （Fatsia japonica）， and the difference multiple reached 15.8 and 4.3 times， respectively. The toxicity sensitivity for different test endpoints were as following： root branch number> total root length> total root surface area> total root tip number> shoot dry weight> plant height> shoot fresh weight. It indicated that the root elongation indexes are more sensitive to Cd toxicity than other endpoints. The SSD based on EC₅₀ of shoot dry weight and root branch number showed almost consistant sensitivity distribution for most plants，among them， Ligustrum japonicum ‘Howardii’ and Pittosporum tobira were sensitive plants to cadmium toxicity and Fatsia japonica were proved to be tolerant plant to cadmium toxicity. At the same time， the thresholds HC₅ of ecological risk to protect 95% plant quality without cadmium toxicity were derived according to SSD.

Key words: shrub seeding, cadmium toxicity, resistance, sensitivity, ecological risk

摘要：

为探究灌木幼苗及不同测试终点对镉（Cd）毒害的抗性和敏感性差异，选取了12种常见的灌木植物，通过Cd对灌木幼苗毒害的水培试验，测定不同含量Cd处理［0（对照）、0.5、1.0、2.0、4.0、8.0、16.0、32.0 mg·L^-1］下植物的生长状况（表观毒害症状、株高、地上部鲜重和干重、根系生长状态），比较不同测试终点稳定性，并运用Burr-Ⅲ模型制作物种敏感性分布图（species sensitivity distributions，SSD），分析不同灌木幼苗对Cd的敏感性。结果表明，供试植物在Cd含量为1.0~4.0 mg·L^-1时开始出现表观毒害症状；Cd对不同的植物地上部和根系毒害阈值差异较大，地上部干重减少10%（EC₁₀）和50%（EC₅₀）对应的毒性阈值变化范围分别为0.11（海桐）~1.30 mg·L^-1（八角金盘）和2.58（金森女贞）~10.90 mg·L^-1（八角金盘），差异分别达到了11.8和4.2倍；根分支数对应的EC₁₀和EC₅₀变化范围分别为0.08（金森女贞）~1.27 mg·L^-1（八角金盘）和2.40（金森女贞）~10.30 mg·L^-1（八角金盘），差异分别达到了15.8和4.3倍；不同测试终点的敏感性从大到小依次为根分枝数>总根长>总根表面积>总根尖数>地上部分干重>株高>地上部分鲜重，说明根系指标对Cd毒性更为敏感；基于地上部干重和根分支数的EC₅₀数据得到的SSD表明，大部分植物的敏感性分布趋于一致，其中金森女贞和海桐对Cd毒害最为敏感，八角金盘为Cd毒害的抗性品种；同时，根据SSD得出保护95%林木品质不受Cd毒害的生态风险阈值HC₅。

关键词: 灌木幼苗, 镉毒害, 抗性, 敏感性, 生态风险