外源NO对镉胁迫下番茄活性氧代谢及光合特性的影响

Effects of exogenous nitric oxide on active oxygen metabolism and photosynthetic characteristics of tomato seedlings under cadmium stress

采用水培方法,研究了外源一氧化氮(NO)对镉(Cd)胁迫下番茄幼苗活性氧代谢及光合特性的影响.结果表明:在Cd胁迫下,外施100μmol·L-1硝普钠(SNP)显著增强了番茄超氧化物岐化酶(SOD)、过氧化氢酶(CAT)等抗氧化酶活性,提高了叶片、根系中Ca、Fe等元素含量,提高了叶片叶绿素含量、净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs),降低了过氧化氢(H2O2)、丙二醛(MDA)含量和胞间CO2浓度(Ci).但SNP对Cd胁迫下的缓解效应可被牛血红蛋白(Hb,NO的清除剂)消除.在Cd处理液中加入100μmol·L-1NOx-(NO的分解产物)或100μmol·L-1亚铁氰化钠(SNP的相似物或分解产物),对Cd胁迫无显著改善.表明外源NO可通过提高活性氧清除能力,维持矿质营养元素平衡,缓解Cd胁迫对番茄幼苗叶片光合机构的破坏,从而维持番茄光合效率.

A hydroponic experiment was conducted to study the effects of exogenous sodium nitroprusside （SNP）,a NO donor,on the active oxygen metabolism and photosynthetic characteristics of tomato （Lycopersicon esculentum Mill.） seedlings under Cd stress. The results showed that under the stress,applying 100 μmol·L-1 SNP promoted the activities of plant superoxide dismutase （SOD） and catalase （CAT） significantly,increased the leaf-and root calcium （Ca） and iron （Fe） contents and the leaf chlorophyll content,net photosynthetic rate （Pn）,transpiration rate （Tr）,and stomatal conductance （Gs）,and decreased the contents of H2O2 and MDA and the concentration of intercellular CO2 （Ci）. The addition of hemoglobin,a NO scavenger,eliminated the effects of SNP,while applying 100 μmol·L-1 sodium nitrate or nitrite （the decomposition products of NO or its donor SNP） or 100 μmol·L-1 sodium ferrocyanide （an analog of SNP） had no significant alleviation effects on Cd stress. This study suggested that exogenous NO could promote the scavenging of reactive oxygen,keep the mineral nutrition in balance,and alleviate the damage of Cd stress to the leaf photosynthetic apparatus,making the tomato seedlings preserve their photosynthetic efficiency.