谷子萌发及苗期生理生化指标对铅胁迫的响应

The germination of foxtail millet seeds and the physiological and biochemical indexes of its seedlings in responses to lead stress

【目的】探究重金属元素铅(Pb)对谷子萌发及幼苗生理生化特性的影响,为Pb污染背景下谷子的安全生产和品质保障提供理论依据。【方法】以谷子品种晋谷21号为试验材料,采用土培盆栽试验,以自然土壤加水为对照(CK,0 mg/kg),设5个外源Pb浓度处理(50、100、250、500和1000 mg/kg),分析不同Pb浓度处理对谷子萌发及苗期叶片生理生化指标的影响。【结果】随着Pb浓度的增加,谷子的发芽势、发芽率及发芽指数等萌发指标均受到不同程度的抑制,1000 mg/kg处理的相对发芽率仅有52.5%。叶绿素含量随着Pb浓度的增加呈先升高后降低的变化趋势,各Pb胁迫处理均显著高于CK(P<0.05,下同),Pb浓度为500 mg/kg时,叶绿素a、叶绿素b和叶绿素a+b含量均达最大值,较CK分别增加58.3%、69.5%和64.3%。随着Pb浓度的增加,过氧化物酶(POD)活性、质膜透性、丙二醛(MDA)含量及脯氨酸含量均显著增加,其中POD活性对1000 mg/kg高浓度Pb胁迫尤为敏感。可溶性蛋白质含量随着Pb浓度的增加呈先升高后降低的变化趋势,Pb浓度为500 mg/kg时可溶性蛋白质含量达最大值,较CK显著增加54.1%;Pb浓度为1000 mg/kg时,可溶性蛋白质含量急剧下降,与CK相比显著降低14.9%。相关分析结果表明,谷子的发芽势、发芽率和发芽指数均与Pb浓度呈显著负相关,POD活性、质膜透性、MDA含量和脯氨酸含量均与Pb浓度呈极显著正相关(P<0.01)。不同Pb浓度下抗性指标相对值的平均值(敏感性)排序为:POD活性>质膜透性>脯氨酸含量>MDA含量>可溶性蛋白质含量。【结论】谷子在萌发阶段和幼苗时期均会受到Pb胁迫的影响,同时在响应Pb胁迫时,谷子能通过自身生理生化特性的改变提高其适应Pb胁迫的能力,但这种适应性有一定限度。

【Objective】To investigate the effects of heavy metal lead(Pb)on the germination of foxtail millet seeds and the physio-biochemical characteristics of its seedlings so as provide a theoretical basis for the safe production and quality assurance of this type of special rainfed cereal under the background of Pb pollution.【Method】A pot experiment was conducted using foxtail millet cultivar Jingu 21 as the experimental material to investigate its seed germination and seedling physio-biochemical indexes as influenced by five exogenous Pb concentrations(50,100,250,500,1000 mg/kg).Soil without added Pb was used as the control(CK,0 mg/kg).【Result】The germination energy,germination ratio and germination indexes of Jingu 21 were inhibited with increasing Pb concentrations,the relative germination rate of foxtail millet seeds under Pb treatment of 1000 mg/kg was only 52.5%compared with CK.The contents of chlorophyll increased firstly,and then decreased with increasing Pb concentrations,and all of these kinds of chlorophyll contents were significantly higher than those in the CK(P<0.05,the same below).When Pb concentration was 500 mg/kg,the chlorophyll a,chlorophyll b and chlorophyll a+b contents reached the maximum,which increased by 58.3%,69.5%and 64.3%respectively compared with CK.As Pb concentration increased,peroxidase(POD)activity,Plasma membrane permeability,malondialdehyde(MDA)content and proline content in leaves of Jingu 21 seedlings increased significantly,among with POD activity was especially sensitive to stress of high Pb concentration.Soluble protein content increased first and then decreased with increa-sing Pb concentrations.When Pb concentration was 500 mg/kg,the soluble protein content reached the highest,which was 54.1%higher than that of CK.When Pb concentration was 1000 mg/kg,soluble protein content decreased sharply,which was 14.9%lower than that of CK.The correlation analysis showed that the germination potential,germination rate and germination index of foxtail millet were negatively correlated with Pb concentrations.The POD activity,plasma membrane permeability,MDA content and proline content were positively correlated with Pb concentration(P<0.01).The average relative value of resistance index(sensitivity)at different Pb concentrations was in the order POD activity>plasma membrane permeabilyty>proline content>MDA content>soluble protein content.【Conclusion】Millet is affected by Pb stress during both germination and the seedling stage.Within a certain concentration range,foxtail millet can alleviate the damage caused by Pb stress by adjusting its own physiological and biochemical indexes.