Protection of exogenous silicon and CoQ10 on mitochondria in cucumber (Cucumis sativus L.) roots under salt stress

Chinese. 探明外源Si和辅酶Ｑ10(CoQ10)对NaCl胁迫下黄瓜(Cucumis sativus L.)幼苗根系离体线粒体膜生物物理特性和呼吸功能的保护作用。试验设置3个处理：CK; 加50 mmol/L NaCl; 加1.0 mmol/L K2SiO3 + 50 mmol/L NaCl。处理10 d后取各处理植株根系提取线粒体，在离体线粒体中加入10 mmol/L CoQ10。Si能显著降低盐胁迫下黄瓜线粒体的H2O2含量，抑制线粒体的脂质过氧化，增加线粒体膜的流动性和膜电位(ΔΦM)，降低膜的肿胀度，使线粒体呼吸控制比(RCR)和氧化磷酸化效率(P/O)显著升高，提高线粒体的呼吸速率。CoQ10也有降低线粒体膜膨胀度，增加线粒体膜流动性和膜电位的作用，同时可以降低线粒体的H2O2和MDA含量，缓解盐胁迫的伤害作用。外源Si和CoQ10能有效缓解盐胁迫对黄瓜根系线粒体膜的损伤，增强线粒体抗膜脂质过氧化能力和膜完整性，提高线粒体的呼吸作用。

English. The purpose of this paper is to clarify the protective effects of exogenous silicon and CoQ10 on the biophysical characters and respiration of mitochondria in vitro from the salt-stressed cucumber (Cucumis sativus L.) roots. The treatments with K2SiO3 (1.0 mmol/L) were divided into three groups: CK group, NaCl group, NaCl＋K2SiO3 group; and the isolated mitochondria were treated with 10 mmol/L CoQ10. The results showed that additional silicon in nutrient solution could significantly decrease H2O2 and MDA contents, increase membrane fluidity and membrane electronic potential (ΔΦM) in mitochondria from salt-stressed cucumber roots, decrease membrane swelling, increase the rate of respiration by prominently increasing respiratory control ratio（RCR）and oxidative phosphorilation ratio (P/O). The addition of CoQ10 in isolated mitochondria also decreased membrane swelling, increased membrane micro-viscosity and electronic potential, decreased the contents of H2O2 and MDA in the meantime, especially under salt stress. The above results suggests that exogenous silicon and CoQ10 may effectively antagonize the afor ementioned changes in mitochondria induced by salt stress, increase its ability of protection against lipid peroxidation and membrane integrity, which leads to the increase of respiratory rate.