外源亚精胺可缓解荇菜镉毒害

研究了外施浓度为0.01 mmol.L^-1的亚精胺(Spd)对不同浓度镉(Cd²⁺⁾胁迫下荇菜(Nymphoides peltatum)叶片的叶绿体结构、叶绿素含量、可溶性蛋白含量、超氧阴离子(O₂^-.)产生速率和丙二醛(MDA)含量, 以及保护酶——超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT) 活性的影响。结果表明, (1) Cd²⁺胁迫可使荇菜细胞的叶绿体结构遭到破坏,叶绿素含量减少。外施Spd则可有效地保护叶绿体结构, 减少叶绿素的流失。(2) 在单一Cd²⁺处理条件下, 随着Cd²⁺浓度的升高, 叶绿素含量呈现先升后降的趋势, 可溶性蛋白含量则逐渐下降。外源Spd处理显著提高了二者的含量, 并延缓了它们的下降速度。(3) 在单一Cd²⁺处理条件下, SOD、POD和CAT活性分别在Cd²⁺浓度为1、 1和2 mg.L^-1时达到最高值, 而后随着Cd²⁺浓度的增加其活性逐渐下降。外施Spd使它们的活性分别提高了5.8%、37.5%和3.3%, 并降低了O₂^-.产生速率和MDA的含量。上述结果表明, Spd增强了荇菜对Cd²⁺毒害的抗性, 并在一定程度上缓解了Cd²⁺对荇菜的毒害。

Exogenous Spermidine Can Mitigate the Poison of Cadmium in Nymphoides peltatum

This study focused on the changes in chlorophyll content, soluble protein content, O₂ ^.- generating rate, MDA content and activity of protective enzymes (SOD, CAT, POD) in leaves of Nymphoides peltatum under different concentrations of Cd²⁺ stress with 0.01 mmol.L^-1 exogenous spermidine. Transmission electron microscopy revealed that Cd²⁺ imposed injury on the ultrastructure of chloroplasts, with swelling, breakage and disappearance of the chloroplast envelope and reduced chlorophyll content. Spermidine treatment effectively protected the ultrastructure of chloroplasts against Cd²⁺ stress and maintained the arrangement of thylakoids. Under single Cd²⁺ stress, with Cd²⁺ increase, chlorophyll content in N. peltatum increased then decreased quickly, whereas soluble protein content decreased gradually. The content was much higher with the addition of sprayed spermidine than with only a single Cd²⁺ treatment, and the trend of decrease was lower. Under single Cd²⁺ stress, the maximal SOD, CAT and POD content appeared at 1, 1 and 2 mg.L^-1 Cd^2+_, respectively, and decreased gradually thereafter ; the activities of these protective enzymes were markedly increased under spermidine treatment, by 5.8%, 37.5%, and 3.3%, respectively, and therefore decreased the generation rate of reactive oxygen species such as O₂ ^-. and MDA content.