【作者】 浦铜良；

【导师】 张承烈；

【作者基本信息】 兰州大学 ， 植物学， 2000， 博士

【摘要】 干旱,高温,低温,高盐等胁迫环境施加于植物时,最为明显的共同点之一是引起植物细胞水分的丧失和氧化伤害,并伴有光合作用的下降。几乎所有生物抵抗非生物胁迫的方法之一是累积或大量累积一些不会干扰正常生化反应的相容性溶质(Compatiblesolutes),即文献中通常出现的渗透物质和渗透保护物质。这些溶质积累可降低细胞水势,增强吸水保水能力,和稳定生物膜和/或保护细胞大分子结构。我们用柱层析等手段从该沙漠地区沙丘芦苇叶片中分离提纯了一种为该生态型芦苇所特有的小分子化合物,分子量为Mr856,易溶于水、稀酸、稀碱和含水醇中,具有多氨基芳香族强极性特征和极强的UV(213nm)和UV-B(287,312nm)吸收,元素组成仅为C、H、O、N,其化学特征与已报道的逆境胁迫诱导累积的相容性溶质均不同。该化合物在叶片中的自然丰度与当地月平均气温和月极端高温为指标的生境高温程度之间呈显著相关性,在夏季高温时期,它在沙芦叶中含量可达0.5-0.6mg/g FW,但如按平均分布于细胞内计算,则其对细胞渗透势降低的作用十分有限(大约1.5mmol/L),可能不具有明显的渗透调节的功能。利用分步离心分离方法证明它大量存在于叶绿体以及类囊体组分中。在实验条件下,表明在高温下该化合物对叶绿体电子传递链的功能具有保护作用,在35 和40℃温度下,离体水芦叶绿体的Hill 放氧活性仅为25℃时的37 和18%左右,而同样条件下经其处理(200μg/ml)的水芦叶绿体仍能保持较高的光合放氧活性,分别为50 和33%。因此推测,该独特小分子化合物可作为一种渗透保护物质通过稳定和保护光合器官的功能等而赋予沙丘芦苇较强的抵御生境高温及干旱的能力,以适应沙漠地带恶劣的生长环境。研究还表明,与当地的水生芦苇比较,沙芦叶片内的多种ROS 清除酶类活力的配合处于一种失衡状态。较高的SOD 和较低的CAT、POD 等活性将导致容易形成.~OH。但沙芦所累积这一特有的小分子物质,有很强的直接清除.~OH 的作用,可高效率地清除胁迫条件下产生的.~OH 自由基,极大地抑制高温高光强下离体叶绿体的膜脂过氧化。在低浓度(200μg/ml)实验条件下的.~OH 清除效率远比已知的.~OH 清除剂甘露醇高。沙芦同时还通过显著地降低叶片叶绿素含量(单位叶面积基础)以减少高光强下光能的摄入,从而更多还原

【Abstract】 It is well documented that environmental or abiotic stresses such as drought, high orlow temperature as well as high salinity have in common their effects on plant water statusand oxidative damage, accompanied by lower photosynthetic rate. On the other hand,almost all the plants often accumulate some metabolites to certain levels in cell inintensifying its anti-abiotic-stress capacity. These stress-induced metabolites, osmolytes orosmoprotectants, usually do not interfere with or have little negative effect on the normalbiochemical metabolic network. Instead, they usually play a multiple role of adjusting cellosmotic potential and maintaining the integration of proteins(enzyme) and biomembraneunder stresses. These metabolites are often termed as compatible solutes. During ourstudy on reeds from different habitat, A small solute was obtained with columnchromatography, which only exists and accumulates in the leaves of dune reed innorthwest China’s desert region. The purified compound showed a dark brown, non-crystalappearance and tasted smell-less and a bit astringent. Chemical composition was onlyC(61.9%), H(5.8%), O(18.1%), N(14.2%), with apparent alkalinity and high polarity. Thecompound was soluble in water, lite acid or alkali, and aquatic alcohol but not in commonesters, ketones, benzene or trichloromethane. It has unique polyamine and aromaticfeatures, which are quite different from those known ones accumulated under stresses byplants and has a very strong absorption in UV(213nm) and UV-B(287, 312nm) fields. Wepreliminarily suggest that the solute is a polyamine aromatic compound (PAAC)The natural quantity of the PAAC was strikingly proportional to monthly average airtemperature or monthly maximum temperature as the index of high-temperaturestress(r=0.91, 0.88 respectively, p<0.05). On other hand, the community of DR is farscattered than that of SR, resulting in higher leaf and air temperature at crown due to theradiation and limited water supply as well. So certain causality could be concludedbetween the accumulation of the PAAC and the adaptation of DR to high temperature ofthe habitat.The accumulated PAAC in July could amount to 0.5-0.6mg/g FW, but which could onlyaccount for a concentration of about 1.5mmol/L if it is equally distributed in cells. Thus if更多还原