香蒲对不同浓度Pb~(2+)胁迫的生理应答及其细胞超微结构变化

通过室内水培试验,研究了不同浓度Pb2+(0、0.25、0.50、1.00和2.00mmol·L-1)胁迫对东方香蒲根和叶中Pb含量、叶绿素含量、丙二醛(MDA)含量、抗氧化酶(SOD、CAT和POD)活性以及亚细胞结构的影响。结果显示:(1)随着外源Pb2+浓度的增加,Pb在香蒲根和叶中的积累量均显著高于对照,且Pb在根中的含量明显高于叶中,并与外源Pb2+浓度呈显著正相关关系。(2)香蒲叶片中的叶绿素a和叶绿素b含量随着外源Pb2+浓度的增加呈先升后降趋势,均在处理浓度为0.50mmol·L-1时达到峰值。(3)胁迫处理叶片的MDA含量与对照相比变化不显著,但根中MDA含量呈显著下降趋势。(4)叶片中SOD活性在1.00mmol·L-1 Pb2+处理时达到峰值,然后下降,但始终高于对照,CAT和POD活性则均低于对照组;根中SOD活性除1.00mmol·L-1 Pb2+处理组外均显著低于对照组,CAT和POD活性分别在0.25和0.50mmol·L-1 Pb2+处理时达到峰值,然后随处理Pb2+浓度升高而下降。(5)电镜观察发现,Pb2+胁迫使香蒲叶细胞中叶绿体被膜破裂,类囊体膨胀、破损;根和叶细胞中的线粒体被膜均破裂、内腔空泡化,细胞核核膜破损、核仁消失、染色质凝集。研究表明,Pb2+胁迫致使东方香蒲根、叶生理代谢失衡,亚细胞结构出现不可逆的损伤,这为从分子水平研究Pb2+作用的具体机理以及香蒲在重金属污染修复中的应用提供了依据。

Physiological Responses and Ultrastructural Changes of Typha orientalis Presl under Pb2+ Stress

Effects of different concentrations of Pb²⁺(0,0.25,0.50,1.00,2.00 mmol·L^-1) on contents of Pb,chlorophyll and malondialdehyde (MDA),activities of antioxidant enzymes (SOD,CAT and POD) and subcellular structure in the leaves and roots of Typha orientalis Presl were studied in this experiment.The results indicated that:(1)with the increase of exogenous Pb²⁺ concentrations,Pb accumulation in roots and leaves were significantly higher than that of the control,and Pb contents in roots were significantly higher than those in leaves,which had significant positive correlation with exogenous Pb²⁺ concentrations.(2)Both contents of chlorophyll a and chlorophyll b in leaves increased first and then decreased,which both reached the peak value in 0.50 mmol·L^-1 Pb²⁺ treatment.(3)There was no significant change of MDA contents in leaves compared with the control,whereas MDA content in roots significantly declined.(4)In leaves,superoxide dismutase (SOD) activity reached the peak value in 1.00 mmol·L^-1 Pb²⁺ treatment and then decreased compared to the control,which was always higher than that of control.However,peroxydase (POD) and catalase (CAT) activities in Pb²⁺ treatment groups were all lower than that of control group.In roots,superoxide dismutase (SOD) activity decreased significantly compared to the control except 1.00 mmol·L^-1 Pb²⁺ treatment.Catalase (CAT) and peroxydase (POD) activities reached their peak values in 0.25 mmol·L^-1 and 0.50 mmol·L^-1 Pb²⁺ treatments,respectively,and then decreased with the increase of exogenous Pb²⁺ concentration.(5) By means of transmission electron microscope technology,it was observed that Pb²⁺ induced damages of cell ultrastructure:chloroplast envelope was damaged,thylakoid swelled and broke in leaves cells;in leaf and root cells,mitochondria were vacuolated and the envelope was broken;nuclear membrane was damaged,nucleolus lost and chromatin condensed.It was concluded that Pb²⁺ stress induced imbalance of physiological metabolism and irreversible damage of subcellular structure.This research could provide theory basis for the specific mechanism of Pb²⁺ stress at the molecular level and application of Typha orientalis Presl in heavy metal pollution repair.