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根系依赖根细胞内线粒体呼吸代谢产生的能量,不断从土壤中获取养分。在胁迫条件下,线粒体的结构和功能会发生一定的变化,从而影响根系的功能。土壤干旱是最容易引起苗木细根衰老死亡的非生物胁迫因子之一。为了更好地认识干旱胁迫下细根线粒体的结构和功能变化,对土壤干旱胁迫下水曲柳(Fraxinus mandshurica)不同颜色细根皮层薄壁细胞内线粒体的超微结构(线粒体数量、形态)、线粒体的呼吸功能、线粒体膜脂质氧化(膜透性变化、过氧化氢含量等)情况进行了研究。结果表明:(1)干旱胁迫下,水曲柳白色及黄色根皮层薄壁细胞内线粒体形状、结构及分布数量与对照相似,无显著差异。干旱胁迫下产生的褐色根皮层薄壁细胞线粒体数量减少,分布密度也变小。线粒体内、外膜先后发生不同程度的解体,最后消失。(2)干旱胁迫显著干扰了线粒体膜的正常呼吸耦联作用,细根线粒体呼吸控制率(RCR)与磷氧比(无机磷酸/分子氧,P/O)均显著低于对照(p<0.05)。随着细根颜色加深,线粒体RCR和P/O值逐渐下降,白色根﹥黄色根﹥褐色根。褐色根线粒体RCR值最低,接近极值1。说明褐色根线粒体结构完整性最差,能量转化效率最低。(3)干旱胁迫下,不同颜色细根线粒体内的H2O2含量、线粒体膜透性、膜脂氧化产物丙二醛(MDA)含量均显著高于对照(p<0.05)。且随着细根颜色加深,各个值增加明显。分析可能是由于干旱胁迫导致线粒体内H2O2含量升高,线粒体膜脂质过氧化(MDA含量升高),膜结构受到破坏(膜透性增加)(电镜下可见部分线粒体内膜电子密度下降及外膜解体)。线粒体膜结构完整性的破坏,直接影响了线粒体呼吸代谢反应,使线粒体呼吸功能下降。
The root system relies on the energy generated by the respiratory metabolism of mitochondria in the root cells, constantly harvesting nutrients from the soil. Under stress conditions, the structure and function of mitochondria will undergo some changes, thus affecting the function of the root system. Soil aridity is one of the most abiotic stress factors that cause the death of fine roots of senescens. In order to better understand the structure and function of mitochondria under drought stress, the effects of soil drought stress on the ultrastructure of mitochondria (mitochondria number and morphology), mitochondria Respiratory function, mitochondrial membrane lipid oxidation (membrane permeability changes, hydrogen peroxide content, etc.) were studied. The results showed that: (1) Under drought stress, the mitochondrial shape, structure and distribution of white and yellow cortex parenchyma cells were similar to the control, no significant difference. The number of mitochondria in the brown root cortex parenchyma cells produced under drought stress decreased and the distribution density also decreased. Mitochondria, the outer membrane has occurred in varying degrees of disintegration, and finally disappear. (2) Drought stress significantly interfered with the normal respiratory coupling of mitochondrial membrane, and mitochondrial respiratory control rate (RCR) and P / O ratio (inorganic phosphate / molecular oxygen, P / O) ). With the deepening of fine root color, mitochondrial RCR and P / O values gradually decreased, white roots> yellow roots> brown roots. Brown root mitochondria RCR lowest, close to the extreme 1. The brown root mitochondria showed the worst structural integrity and lowest energy conversion efficiency. (3) H2O2 content, mitochondrial membrane permeability and malondialdehyde (MDA) content in the mitochondria of different color were significantly higher than those of the control under drought stress (p <0.05). And as the fine root color deepens, each value increases significantly. Analysis may be due to drought stress leading to increased H2O2 content in the mitochondria, mitochondrial membrane lipid peroxidation (MDA content increased), the membrane structure is damaged (increased membrane permeability) (electron microscopy can be seen part of mitochondrial inner membrane electron density decreased and outside Membrane disintegration). The integrity of mitochondrial membrane damage, a direct impact on mitochondrial respiratory metabolism, so that mitochondrial respiratory function decline.