Pb-N复合胁迫对齿肋赤藓生理生化的影响

Effects of Pb-N Combined Stress on the Physiology and Biochemistry of Syntrichia caninervis Mitt.

在全球范围内,氮沉降水平和重金属污染事件的发生频率都在不断上升。为更好地了解苔藓植物对Pb-N胁迫的生理响应,以荒漠典型苔藓植物齿肋赤藓为研究对象,用不同浓度的硝酸铅(Pb(NO_(3))_(2))或硝酸铵(NH4NO_(3))及混合溶液胁迫处理,测定植株体内叶绿素含量、渗透调节物质含量、抗氧化酶活性等相关生理指标。结果表明:Pb、N单一处理均会显著降低齿肋赤藓Chl(a+b)含量,但可相应提高Chl(a+b)值。齿肋赤藓可通过提高渗透调节物质含量(Pro、SS)和抗氧化酶活性(SOD、POD、CAT)来耐受低浓度Pb胁迫,过量N处理显著降低了齿肋赤藓渗透调节物质含量(Pro、SS、SP),抑制了抗氧化酶活性(POD、CAT),形成了铵毒害。在Pb-N联合处理下,齿肋赤藓的叶绿素与渗透调节物质含量以及抗氧化酶活性会随着混合溶液中Pb浓度的升高而增加,较同浓度单一N处理下会得到一定程度的恢复。综合分析说明过量Pb、N对齿肋赤藓植株产生明显毒性,Pb、N联合添加存在一定的拮抗作用。齿肋赤藓在Pb-N复合胁迫下表现出交叉适应性。Pb是Pb-N复合胁迫的主导因子,同时,适度的Pb对齿肋赤藓的过量N胁迫有一定程度的缓解作用。

Nitrogen deposition and heavy metal pollution events are increasing all over the world.In order to better understand the physiological responses of bryophytes to Pb-N stress,Syntrichia caninervis Mitt.,a typical desert bryophyte,was selected to determine the chlorophyll content,osmotic adjustment substance content and antioxidant enzyme activity under different concentrations of Pb(NO_(3))_(2) or NH4NO_(3) and their mixed solution.The results showed that the content of Chl(a+b)was significantly decreased by Pb and N treatment,while Chl(a+b)value was increased.Under a single stress treatment,Syntrichia caninervis can tolerate low Pb stress by increasing the content of osmotic adjustment substances(Pro and SS)and the activity of antioxidant enzymes(SOD,POD,CAT).Excessive N treatment significantly reduced the contents of osmotic regulators(Pro,SS,SP),inhibited the activity of antioxidant enzymes(POD,CAT),and resulted in ammonium toxicity.Under combined Pb-N treatment,the contents of chlorophyll and osmotic adjustment substances and the activity of antioxidant enzymes increased with the increase of Pb concentration in mixed solution,compared with the treatment of the same concentration of single N,a certain degree of recovery can be obtained.Comprehensive analysis showed that excessive Pb and N had obvious toxicity on Syntrichia caninervis,and the combined addition of Pb and N had certain antago nistic effect,which means that Syntrichia caninervis showed cross adaptability under combined Pb-N treatment.It was also found that Pb was the dominant factor of Pb-N compound stress,meanwhile,moderate Pb concentration can alleviate excessive N stress of Syntrichia caninervis to some extent.