摘要: 镉(Cd)是重要的重金属污染源,一氧化氮(NO)是近年来发现的一种普遍存在于生物界的信使分子,研究表明其参与了植物对Cd胁迫的应答反应调控。文章用硝普纳(SNP)作为NO供体,向番茄幼苗喷洒100 mol·L-1 SNP 1 d后加入50 mol·L-1 Cd 处理7 d,取完全展开叶片,提取叶绿体进行光谱学研究,分别测定了叶绿体室温吸收光谱、叶绿体低温荧光光谱和DCPIP电子传递效率等指标,研究外源NO缓解Cd对叶绿体毒性的影响。结果发现,Cd对叶绿素a、叶绿素b和类胡萝卜素含量都有不同程度的降低,NO处理缓解了Cd的影响,使叶绿体室温吸收光谱的吸收率提高;Cd导致686 nm处峰(PSII)偏移4 nm,峰值降低33%,734 nm处峰值降低23%,外源NO缓解了Cd对光合系统的影响,使得叶绿体低温荧光光谱在686和734 nm的峰值分别仅下降17%和10%;以DCPIP为人工电子受体,Cd处理的叶绿体中DCPIP还原速率较慢,光合电子传递(H2O→DCPIP) 速率降低1.5倍,外源NO处理显著缓解了Cd对电子传递链的抑制,使其光合电子传递速率恢复到对照的水平。该研究可为NO处理增强植物对Cd胁迫的抗性提供理论依据。
关键词:一氧化氮;镉;叶绿体;光合作用;重金属污染
Abstract:Cadmium (Cd) is an important heavy metal pollution, and NO is a bioactive molecule, which was found to participate in the reaction of plant to Cd. Leaves from tomato seedlings pretreated with 100 μmol·L-1 sodium nitroprusside (SNP, as NO donor) 1 day prior to being treated with 50 μmol·L-1 Cd for 7 days were used as materials, and chloroplasts were isolated from the leaves to study the effects of NO on the spectroscopic characteristics of chlorophyll. The results of absorption spectra of chloroplasts showed that NO alleviated the effects of Cd on absorption spectra of chloroplast by raising the relative absorbance at 436 nm, 480 nm and 470 nm, which caused lower contents of carotinoid and chlorophyll. Fluorescence emission spectra of chloroplasts indicated that NO alleviated effect of Cd, and the relative absorbance at 686 nm and 734 nm decreased 17% and 10% respectively, while they decreased 33% and 23% respectively in chloroplasts treated with Cd. DCPIP analysis results showed that NO alleviated the inhibition of photosynthetic electron transport by Cd, and consequently the electron transport rate reached the same level of control.
Key words:Nitric oxide;Cadmium;Chloroplast;Photosynthesis;Heavy metal pollution
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