Cadmium (Cd) is a common abiotic stress factor in the environment.Screening germplasm resources for Cd tolerance is an effective way to develop plants for use in biofuel production on l and contaminated by heavy metals.Switchgrass (Panicum virgatum) has been identified by the U.S.Department of Energy as having very high potential as a biofuel substrate.Hence, 14switchgrass cultivars under hydroponic culture were treated with 0 (control) or 10μmol·L-1 Cd, and morphological and physiological traits were investigated.Root morphology data of switchgrass were obtained using an EPSON scanner and WinRHIZO software.Net photosynthetic rate was determined with the LiCor-6400 portable photosynthesis system and a spectrophotometer was used to determine root activity.Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to examine Cd accumulation of switchgrass.Data for measured traits were transformed to units of statistical st andard deviation by division by their st andard error and aggregated with positive/negative sign reversal where relevant, so that Cd tolerance was additive across traits, and a composite index of Cd tolerance compiled.Lastly a cluster analysis was performed.It was found that Cd stress significantly reduced the root length, root surface area, number of root tips, total dry weight, net photosynthetic rate and root activity of different switchgrass cultivars to different degrees.Significant differences were found (P＜0.01) among cultivars.According to composite index (Dvalue), Kanlow was the most tolerant variety, while Foreburg was the least tolerant.On cluster analysis, the 14switchgrass cultivars were classified into 3Cd-tolerance types.One cultivar (Kanlow) had high Cd tolerance;9cultivars (Alamo, BoMaster, Carthage, Cave in Rock, Long Isl and, Newyork, Shawnee, Sunburst, Trailblazer) were medium-cadmium-tolerance types and 4cultivars (Blackwell, Dacotah, Foresburg, Shelter) were Cd-sensitive types.It was also found that the cultivar Kanlow with high Cd tolerance had a strong ability to accumulate Cd.This study provides a theoretical basis for selecting suitable switchgrass cultivars for the cultivation of Cd-polluted l and, and the results illustrate an operable method to evaluate the Cd tolerance of plant germplasm lines.%镉 (Cd) 是环境中常见的非生物胁迫因子, 从种质资源中筛选出不同耐镉型的植物材料有利于能源植物在重金属污染土地上的高效开发利用.基于此, 本研究以14个能源植物柳枝稷品种为供试材料, 外源施加浓度为10μmol·L-1镉, 结合形态和生理指标, 采用隶属函数及标准差系数权重法综合评价了柳枝稷幼苗对Cd的耐受性.结果表明:10μmol·L-1 Cd胁迫显著降低了柳枝稷根长、根表面积、根尖数、总生物量、净光合速率及根系活力, 且品种间差异显著 (P＜0.01) .根据隶属函数法得到柳枝稷对镉耐受性综合评价值 (D), 其中Kanlow最高, Forestburg最低.采用系统聚类法对D值进行聚类分析, 结果表明, 14份柳枝稷可分为3组不同耐镉型材料, 其中强耐镉型材料1份, 为Kanlow;中等耐镉型材料9份, 分别为Alamo、BoMaster、Carthage、Cave in Rock、Longisland、Newyork、Shawnee、Sunburst、Trailblazer;镉敏感型材料4份, 分别为Blackwell、Dacotah、Forestburg、Shelter.结合柳枝稷对Cd的吸收, 进一步分析发现耐镉性较强的品种镉富集能力也较强.可为选择适宜的柳枝稷材料种植于镉污染土地上提供理论依据, 同时为丰富评价植物耐镉种质资源提供可操作性的方法.
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