外源NO对镉胁迫下长春花质膜过氧化ATP酶活性及光合特性的影响

为了解镉胁迫下外源NO对地被植物生理响应的调控机制，采用盆栽试验研究了外源NO（SNP）对镉胁迫下长春花幼苗生长、活性氧代谢、质膜ATP酶活性及光合特性的影响。结果表明，外施100μmol·L^-1SNP能缓解25mg·kg一镉胁迫对长春花幼苗生长的抑制，增加叶长、叶宽、株高、基径和生物量。与镉胁迫相比，施用SNP能够降低叶片和根系中丙二醛（MDA）、过氧化氢（H2O2）含量和过氧根离子自由基（O2^-·）产生速率，提高过氧化氢酶（CAT）、过氧化物酶（POD）、超氧化物歧化酶（SOD）活性及还原型谷胱甘肽（GSH）含量。SNP能显著缓解镉胁迫对叶绿素a（Chla）、叶绿素b（Chlb）和总叶绿素的抑制，提高叶片净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）和气孔限制值（Ls），降低胞间CO2浓度（G）和瞬时光能利用效率（LUE）。同时，外源NO能诱导叶片和根系中质膜H＋-ATPase和Ca2＋-ATPase活性提升到正常水平（对照）。但外施100μmol·L-1 NO分解产物NaNOx或SNP相似物Na3Fe（CN）6对镉胁迫则无明显缓解作用。因此，外源NO可通过提高活性氧清除能力，增加叶绿素含量，增强质膜ATP酶活性，从而提高叶肉细胞光合能力，加强离子跨膜运输和信号转导，缓解镉胁迫对细胞质膜的损伤。

Effects of Exogenous Nitric Oxide on Lipid Peroxidation and ATPase Activity in Plasma Membrane and Photosynthetic Characteristics of Catharanthus roseus Under Cadmium Stress

Ornamental plant Catharanthus rose us is an important landscaping and anticancer drug source plant that widely grows in the city gardens and on the roadsides in China. A controlled pot-experiment was carried out to investigate the effects of exogenous nitric oxide（NO） supplied with the sodium nitroprusside （SNP, an exogenous NO donor） on growth, photosynthetic characteristics, and the reactive oxygen metabolism and ATPase activity in plasma membrane of Catharanthus roseus tissues under cadmium stress. The results showed that addition of 100 μmol·L^-1 exogenous SNP alleviated the inhibitory effects of 25 mgCd·kg^-1 on the growth of C. roseus seedlings, increased the leaf length and width, plant height, basal diameter and biomass （fresh and dry weight） of the plants. Applying SNP decreased the contents of malondialdehyde （MDA）, hydrogen peroxide（H2O2）, and glutathione （GSH） and the production rate of superoxide anion radical （O2^-）, but significantly promoted the activities of catalase（CAT）, peroxidase（POD ） and superoxide dismutase（SOD ） in the leaves and roots compared with no SNP treatment. Also, SNP supply alleviated the Cd inhibitory effects on chlorophyll a（Chla）, chlorophyll b （Chlb） and total chlorophyll, increased the net photosynthetic rate （Pn）, stomatal conductivity degrees （Gs）, transpiration rate （Tr） and stomatal limit value （Ls）, and decreased the intercellular CO2 concentration （Ci） and instantaneous light use efficiency （LUE）. Furthermore, exogenous NO elevated H＋- ATPase and Ca2＋-ATPase activities of plasma membrane in the leaves and roots to the levels without Cd stresses. However, applying 100 μmol·L^-1 sodium nitrate or nitrite （the decomposition products of NO） or the same concentration of sodium ferrocyanide （an analog of SNP） had no significant alleviating effects on cadmium stress. These results suggest that exogenous NO could mitigate Cd damages to the cell membrane of C. roseus seedlings via scavenging reactive oxygen species, increasing chlorophyll contents and promoting ATPase activity in the plasma membrane.