环境胁迫对库拉索芦荟叶片超微结构影响研究

对1年生库拉索芦荟分别用盐(1.8%的NaCl)、低温(10℃)、干旱[25%(w/v)的聚乙二醇-6000]3种胁迫条件处理7d后,对其叶肉细胞超微结构进行观察.结果发现:3种胁迫处理均可使库拉索芦荟细胞膜系统、叶绿体、线粒体、细胞核等结构受到不同程度的破坏,叶绿体周围出现许多小泡,导致细胞内膜系统紊乱,细胞器结构稳定性降低;盐胁迫下高尔基体在细胞质中解体;盐和低温胁迫下均可见线粒体膜与叶绿体膜发生融合、线粒体嵌在叶绿体当中的现象.另外,本研究发现,盐胁迫、低温胁迫比干旱胁迫对库拉索芦荟细胞膜的损伤更严重,而水分胁迫对其的伤害程度较小,表明库拉索芦荟的抗旱性较其抗盐性更强.     

盐胁迫对玉米叶片叶肉细胞生物膜超微结构的影响

研究了NaCl胁迫对玉米叶肉细胞生物膜超微结构的影响. 结果表明：NaCl胁迫破坏了玉米叶片叶肉细胞生物膜的正常结构,50 mmol·L^-1 NaCl处理胁迫下,玉米叶肉细胞核膜,线粒体膜,细胞膜,叶绿体膜,液泡膜都受到不同程度的破坏,叶绿体基粒类囊体膨胀,间质片层空间增大,片层紊乱。100 mmol·L^-1 NaCl处理胁迫下,质膜,液泡膜,线粒体,叶绿体都受到严重的破坏。细胞质膜破坏,破损的叶绿体充斥在细胞间隙中;叶绿体外膜破坏,甚至解体消失,叶肉细胞中充满膜结构,基粒排列方向改变,垛叠层数减少,基粒和基质片层界限模糊不清,有的基粒解体消失,甚至叶绿体完全解体;核膜破坏、解体,核中的染色质高度凝缩;线粒体的数量增多,线粒体膜破坏,脊的数量减少,甚至整个线粒体破损解体;液泡膜破坏;由于各种生物膜的破坏,使细胞内充满许多囊状小泡、多泡体或斑层小体;叶肉细胞发生严重的质壁分离,严重时发生细胞壁断裂;甚至整个细胞溶解。     

黄河三角洲不同生态型芦苇对盐度适应生理的研究 Ⅱ.不同生态型芦苇的光合气体交换特点

黄河三角洲不同生态型芦苇光合速率和气孔导度有明显差异 ,随生境盐度的增加而降低 ,气孔限制因素是盐胁迫下芦苇光合降低的原因之一。低盐度生境中生长的芦苇的 Rn BPCase活性均大于高盐度下的 ,而 PEPCase活性均小于高盐度下的 ,表明在盐渍条件下 ,叶肉光合器官光合活性的降低也限制芦苇的光合速率。随盐度升高 ,Ru BPCase与PEPCasc活性之比降低。高 PFD下 ,盐胁迫加剧 Fv/Fm降低程度。此外 ,在高盐度下由于叶片蒸腾下降而导致的叶温较高也可能与光合活性降低有关。     

盐胁迫对大麦胚根细胞膜系统的影响

研究了大麦种子在盐下吸胀时胚根细胞超微结构的变化，电镜观察发现，盐胁迫下胚根细胞的膜系统修复困难，细胞器分室重建受阻；并且，这种伤害作用随着盐时间的延长而加剧。作者认为，盐胁迫下吸胀对种子伤害很可能是由于盐离子毒害造成膜系统修复不完善所致。     

Na2CO3胁迫对星星草叶肉细胞超微结构的影响

利用透射电镜技术对Na2CO3胁迫下星星草叶肉细胞超微结构进行了观察。结果表明：未胁迫的叶肉细胞排列疏松,各种细胞器结构完整,叶绿体含少量淀粉粒和脂质球。轻度盐胁迫（2g/L,4g／LNa2CO3）对叶肉细胞超微结构影响较小。中度盐胁迫（6g／L,8g／L Na2CO3）引起叶肉细胞超微结构的变化,叶绿体类囊体肿胀,基粒紊乱,不含淀粉粒,脂质球数量增加,叶绿体由原来的梭形或椭球形变成圆球状;部分线粒体嵴消失,出现晶体结构;中央大液泡破裂;核逐渐降解。高度盐胁迫（10g／L,12g／LNa2CO3）下,叶绿体片层结构消失,脂质球数量增加,体积变大,被大量的膜片层所包围,叶绿体内、外膜消失,叶肉细胞中看不到叶绿体的存在;膜片层包围线粒体;叶肉细胞中可见大量的泡状结构和膜片层,叶肉细胞死亡。上述结果表明,细胞器特别是叶绿体膜结构的破坏与盐胁迫叶肉细胞最终死亡密切相关。     

盐胁迫下盐穗木HcThi1基因的表达分析

环境胁迫能够导致植物的DNA损伤,而DNA损伤修复基因与盐胁迫可能具有密切的相关性。根据盐穗木盐胁迫下响应的转录组测序结果,克隆获得了盐穗木具有DNA损伤修复功能的硫胺素噻唑合成酶(thiazole biosynthetic enzyme)基因,其开放阅读框1 077 bp,编码358个氨基酸,命名为HcThi1。保守结构域分析显示,保守结构域分析发现其具有SDR超家族保守结构域,合成硫胺素噻唑。系统进化树分析显示HcThi1为独立的分支,亚细胞定位于细胞质,为无信号肽的不稳定蛋白。实时荧光定量PCR分析表明,在100 mmol/L NaCl胁迫72 h后,同化枝中HcThi1的表达迅速上调并达到最大值,约为对照组的18.66倍,随着盐浓度的提高,HcThi1的表达逐渐降低。说明HcThi1基因表达受盐胁迫的诱导。研究结果有助于阐明HcThi1基因表达与植物抗盐的相关性。     

水分胁迫引起的两种不同生态型芦苇的DNA损伤与修复

利用DNA解链荧光分析（FADU）法检测两种不同生态型芦苇（Phragmites communis T.)在PEG6000胁迫处理后的DNA损伤。结果表明：无论是20％还是30％PEG6000胁迫处理,耐旱性强的沙丘芦苇的DNA损伤都比耐旱性弱的沼泽芦苇较轻。利用不同浓度的二乙基二硫代谢氨基甲酸钠（DDC）、H2O2、FeSO4以增加芦苇的3种活性氧（O2^-、H2O2、OH）的实验也同样显示出沙丘芦苇抵抗水分胁迫引起的DNA损伤的能力较强。同时,当加入外源活性氧清除剂二甲基亚砜（DMSO）、抗坏血酸（Vc）时,水分胁迫处理的芦苇DNA损伤表现出不同程度的减轻。当PEG胁迫处理的芦苇复水后,DNA损伤随复水时间延长而逐渐减轻,但沙丘芦苇的DNA损伤修复较快而完全。实验初步证明：水分胁迫可引起植物体内DNA损伤且该损伤与活性氧有关,植物的抗旱性与DNA损伤及修复密切相关。     

植物响应金属胁迫重要蛋白质的细胞定位

土壤中的Hg2+、Pb2+、Cd2+、Cu2+、Zn2+、Mn2+、Fe2+/Fe3+等金属离子对植物体具有毒害作用。植物体通过定位于细胞壁、细胞膜,以及各种细胞器中的蛋白质应答重金属胁迫过程。植物体利用细胞壁蛋白质与重金属离子络合,细胞膜系统的转运蛋白与通道调节金属离子运输、细胞器或细胞质基质中的分子伴侣帮助蛋白质折叠等机制完成抑制金属离子进入体内或在体内的解毒等过程。综述了近年来植物响应金属离子胁迫重要蛋白质的细胞定位与作用机制。     

水盐梯度下克里雅河流域芦苇光合响应特征

选择新疆克里雅河流域地下水埋深不同的样点芦苇为材料,采用Li-6400便携式光合系统仪对各样点芦苇的光合响应特征进行实地测定,探讨其适应干旱胁迫和盐胁迫环境的光合机理。结果显示:(1)在干旱区,当地下水位大于2m时,芦苇的光饱和点、表观量子效率、光呼吸速率随地下水位的下降显著降低,而水分利用效率却随着地下水位的下降呈上升趋势;随着地下水位的下降,芦苇的羧化效率、最大净光合速率、CO2饱和点显著下降,水分利用效率随之增大;1.6m地下水位的芦苇相对于2.7m地下水位下芦苇的最大净光合速率、光饱和点、光补偿点、暗呼吸速率分别下降19.98%、40.61%、37%、74.56%。(2)在盐胁迫下芦苇的光合参数整体低于受干旱胁迫的参数;盐胁迫下的芦苇水分利用效率大于受干旱胁迫环境。(3)与陆生环境下的芦苇相比,渍水条件下芦苇的最大净光合速率、光饱和点、光补偿点分别下降41.32%、14.56%、55.55%。研究表明,提高空气CO2供应量可降低水分利用效率从而缓解芦苇盐胁迫伤害,并且可通过调节气孔开闭程度显著增加水生芦苇最大净光合速率,这种变化是植物自身对环境因素变化的生理性反馈和适应性选择对策的结果。     

铜离子胁迫对两种地衣细胞结构的影响

采用光学显微镜徒手切片技术和透射电子显微镜超薄切片制备技术,以两种叶状地衣即中国树花(Ramalina sinensis)和地卷(Peltigera rufescens)为实验材料,研究了不同浓度CuSO4(0、1、2、3、4mmol/L)处理24h后地衣体细胞的存活率以及Cu2+胁迫对细胞超微结构的影响。结果显示:(1)光学显微镜下可初步确定,Cu2+浓度越大中国树花共生藻细胞存活率越小,而同样处理条件下地卷共生藻细胞的存活率则基本保持不变。(2)低浓度Cu2+(1mmol/L)对中国树花细胞结构基本无影响,细胞壁、细胞膜及细胞内的线粒体、叶绿体完整;随着Cu2+浓度增加,当处理Cu2+浓度为2mmol/L时,细胞壁无损,但细胞膜开始破坏形成小空泡,线粒体嵴变凌乱,叶绿体也出现皱缩,类囊体膨胀,基粒排列紊乱;当Cu2+处理浓度大于2mmol/L时,共生藻的细胞膜和细胞器出现不同程度的损伤;当Cu2+浓度为3mmol/L时,细胞壁变薄,细胞膜形成的空泡变大,细胞内部结构变松散,蛋白核消失,叶绿体与细胞质混在一起,基粒片层扭曲,分布混乱,线粒体变形;当Cu2+浓度达4mmol/L时,细胞结构完全受到破坏。(3)不同浓度Cu2+处理对地卷共生藻细胞结构无明显的影响,在所有处理条件下地卷共生藻细胞壁、细胞膜都完整,且大多数共生藻细胞处于分裂状态。研究认为,中国树花对Cu2+胁迫较敏感,Cu2+耐受在1~2mmol/L之间,Cu2+浓度与中国树花细胞结构的损伤程度存在着明显的剂量效应关系,Cu2+浓度越高,其属于共球藻的真核共生藻细胞受损程度越大;地卷对Cu2+胁迫具有一定的耐性,Cu2+胁迫下地卷属于蓝藻的原核共生藻细胞仍能繁殖分裂产生子代细胞。     

Changes of element ratios of cultured cells from dune reed under adverse environmental conditions

Dune reed, as an ecotype of reed plant (Phragmites communis Trin.), is an ideal material for studies on the adaptations of plant to environmental conditions. Scanning electron microscope, energy-dispersive X-ray analysis, and plant tissue culture techniques were used to investigate the effect of extreme temperature, salt, and polyethylene glycol-induced osmotic stress on the intracellular elements K, Na, Ca, and Cl in cultured cells from dune reed and swamp reed (as control). The results indicated that the percentages of the studied elements in dune reed cells exposed to various stresses increased or decreased obviously compared to the swamp reed cells. It has been found that a pattern of absorbing K and discharging Na exists in dune reed cells, which did not exist in swamp reed cells. The pattern is thought to be a significant physiological mechanism of the dune reed response to adverse environmental factors. In addition, the percentages of Ca and Cl in dune reed cells were also shown to increase at high temperature. The growth of cells along with their surface features under different stress conditions were observed and the results are discussed.     

两种生物型芦苇胚性悬浮培养物对渗透胁迫的生理响应 Ⅱ．抗氧化酶类活性的变化

渗透胁迫处理下,沙丘芦苇和沼泽芦苇培养细胞的H2O2含量变化不大,MDA含量随时间延长而降低。抗氧化酶中,沙丘芦苇的SOD、CAT、POD和APx的活力均显著高于沼津芦苇,显示出比沼泽芦苇更强的ROS清除能力。胁迫初期（0．5h-1d)沙丘芦苇细胞中主要表现出SOD、CAT活力的提高,胁迫2d后4种酶活力均明显被诱导。两种生态型芦苇的PEG适应性培养物APx及SOD酶活力显著提高,POD活性仅沼泽芦苇中升高。提示SOD、CAT主要参与沙丘芦苇在渗透胁迫下的短期响应,而APx与长期响应有关。     

四种生态型芦苇叶片结构的研究

The leaf anatomy and uhrastructure of the vascular bundle sheath cells of four ecotypes of reed (Phragmites communis Trin. ) were observed with light and electron microscope. The four ecotypes were the swamp reed, dune reed, heavy salt meadow reed and the light salt meadow reed. It was shown that the intracellular content of the vascular bundle sheath cells of the swamp reed was lower than that of the dune reed; that of the heavy salt meadow reed was between that of the former two reeds and that of the light salt meadow reed and that of the light salt meadow reed was similar to the dune reed. The chloroplasts in the swamp reed were round-shaped with poorly developed grana. Starch grains were not visualized. The uhrastructure of their chloroplasts were similar to those in the typical C3 plants as wheat. By contrast, the chloroplasts in the vascular bundle cells of the dune reed were elliptical with their structure similar to that of the typical C4 plants as maize. These chloroplasts contained some poorly developed grana thykloid. The chloroplasts of the vascular bundle sheath cells in the heavy salt meadow reed were similar to those seen in the dune reed, however, those in the light salt meadow reed appeared to be beth round .and elliptical in shape. The above results suggested a great habitat variation did occur among the four ecotypes of reed in which these exists an obvious evolutional trend from C3 to C4 plants.     

四种生态型芦苇叶片结构的研究

采用光学显微镜和电子显微镜对４种生态型芦苇（ＰｈｒａｇｍｉｔｅｓｃｏｍｍｕｎｉｓＴｒｉｎ．）叶解剖结构及叶脉维管束鞘细胞超微结构进行了观察研究。结果表明,沼泽芦苇维管束鞘细胞内含物较少,维管束鞘细胞叶绿体呈近圆形,超微结构与典型Ｃ３植物小麦鞘细胞的相似,基粒发育退化,不含淀粉粒;沙丘芦苇鞘细胞内含物较多,鞘细胞叶绿体呈近椭圆形,超微结构与典型Ｃ４植物玉米的相似,具有不发达的基粒;重度盐化草甸芦苇鞘细胞内含物则较沼泽芦苇多,而较沙丘芦苇少,鞘细胞叶绿体形态、超微结构与沙丘芦苇相似;轻度盐化草甸芦苇鞘细胞内含物与沙丘芦苇相似,但是,其鞘细胞含有与沼泽芦苇鞘细胞内叶绿体形态相似的近圆形以及与沙丘芦苇和重度盐化草甸芦苇鞘细胞内形态相似的近椭圆形两种形态的叶绿体。表明生长在同一地区不同环境中的４种生态型芦苇的光合结构发生了深刻的变异,表现出从Ｃ３向Ｃ４进化的明显趋势。     

外源多氨基芳香族化合物对高温强光下芦苇离体叶绿体叶绿素降解的缓解作用

以甘肃省河西走廊临泽县境内荒漠地区2种生态型芦苇为主要研究材料,研究了在添加多氨基芳香族化合物(Mr856,PAAC)条件下,不同温度、光照强度处理及处理时间对沙芦和水芦离体叶绿体叶绿素相对含量的影响,以探究PAAC对高温强光条件下离体叶绿体可能的保护机理。结果表明:(1)外源PAAC对水芦和沙芦离体叶绿体叶绿素相对含量的影响因环境光照强度、温度和处理时间的不同而异;(2)光照强度对离体叶绿体叶绿素相对含量的影响与温度有关,且随着处理时间的延长而增强,在光照水平为1 000μmol.m-2.s-1下,沙芦叶绿素相对含量在不同温度下均高于水芦;(3)外源PAAC可明显减缓高温强光胁迫下水芦叶绿素相对含量的降低趋势,尤其对强光胁迫下叶绿素相对含量降低的效应更明显。研究结果说明,PAAC可能作为沙芦叶片中具独特分子结构特征的相容性溶质,可减缓高温强光下离体叶绿体叶绿素的降解,对离体叶绿体有一定的保护作用。     

河西走廊芦苇的光合碳同化途径对生境条件的适应

 本文以甘肃省河西走廊生长的四个不同生境芦苇为对象,比较研究了它们的叶解剖结构、光合关键酶活力、乙醇酸氧化酶活力和稳定碳同位素组成(δ13C)。结果发现,沼泽芦苇叶中虽具有不典型的花环结构,但维管束鞘细胞中不含叶绿体,RUBPcase活力／PEPcase活力比值为24.4,乙醇酸氧化酶活力为1218Unit mgpro-1·min-1δ13C值为-34‰,这些测值位于C3植物(小麦)的范围内。生长于沙丘上的芦苇叶片具有明显的花环结构,维管束鞘细胞内含异型叶绿体,RUBPcase活力／PEPcase活力比值为0.985, 乙醇酸氧化酶活力为504 Unitmgpro-1·min-1,δ13C值为-20.9‰,这些测值与典型C4植物(玉米)十分相似。盐化草甸芦苇和盐化草一沙丘过渡地带芦苇叶中均具有明显的花环结构,维管束鞘细胞中含大型叶绿体,RUBPcase活力／PEPcase活力比值分别为2.45和1.53,但乙醇酸氧化酶活力分别为1470和2058Unitmgpro-1·min-1,δ13C值分别为35.6和30.6‰,综合盐化草甸芦苇和过渡地带芦苇的上述指标,似介于沼泽芦苇和沙丘芦苇之间。由这些结果可以认为,分布于甘肃省河西走廊的芦苇,在种内发生有由环境因子引起的光合碳代谢途径的适应性改变。     

Analyses of Soluble Protein,Total and Free Amino Acids in Leaves of Different Ecotypes of Phragmites communis Growing in the Hexi Corridor

The difference of total and free amino acids and protein extracted from the leaves of four different reed ecotypes growing in Hexi corridor of Gansu Province were investigated. In all of the different reed ecotypes, the content of Asp, Glu, Gly, Leu and Ala in total amino acids were high, while the contents of Ala, Phe, Met and Thr, Pro in total amino acids varied among different reed ecotypes. Albeit Ala, Glu, Asp, Gly and Ser were the chief composition of free amino acids in leaves of all reed ecotypes, but temarkble difference was found in the content of each free amino acid from different reed ecotypes. The content of free Pro in leaves of salt meadow and salt meadow-sand dune transitional zone reed were 3.5 and 1.6 times respectively as much as in leaves of swamp reed. Swamp reed had 11 soluble proteins whereas other three reed ecotypes show that each has 13 soluble proteins. Three “salt adaptation proteins” (66 kD, 40.3 kD, 16.5 kD) were found in leaves of three reed ecotypes with varying degree of salt stress, however, the contents of 3 “salt adaptation protens” showed a negative correlation with the degree of salt stress. There was a large amount of “special protein” (11.7 kD) in leaves of sand dune reeds. These results suggest that the difference in cytogene expression takes a priority basis of adaptation of reed plants to different habitats, while a closer relationship of reeds tolerance to salt or drought stress with Pro accumulation in cells is seen than with the of accumulation stress adaptation protein.     

The survival mechanism of dune reed (Phragmites communis) cultures under high sodium chloride concentration

Adaptations to salt stress were studied in embryogenic cultures from two ecotypes of reed (Phragmites communisT.). In the 600 mM NaCl treatment, relative cell viability of dune reed embryogenic cultures from a desert region was 56% greater than the control, 198% greater than swamp reed embryogenic cultures. After treatment with different NaCl concentrations, their relative growth rates (RGRs), pyridine nucleotides, activities of antioxidant enzymes and plasma membrane H⁺-ATPase (EC 3.6.1.35) were determined. The results showed that NADPH content, NADPH/NADP⁺ ratio and the activity of plasma membrane H⁺-ATPase in dune reed embryogenic cultures were higher than those of the control in the present of 600 mM NaCl. The activities of peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6) increased more in dune reed embryogenic cultures than in swamp reed embryogenic cultures. Dune reed embryogenic cultures tolerated higher concentration of NaCl than swamp reed embryogenic cultures. Under high concentration of NaCl, the survival of dune reed embryogenic cultures might be due to reductive status maintenance and ions absorption regulation in the plant cells. This phenomenon would be a result of cross-adaptation in nature.     

Isolation and characterization of plasma membrane Na(+)/H(+) antiporter genes from salt-sensitive and salt-tolerant reed plants

We isolated cDNAs for Na(+)/H(+) antiporter genes (PhaNHA1s) from salt-sensitive and salt-tolerant reed plants. A phylogenetic analysis and localization analysis using yeast strains expressing PhaNHA1-GFP protein showed that PhaNHA1s were plasma membrane Na(+)/H(+) antiporters. Yeast strains expressing PhaNHA1 from salt-tolerant reed plants (PhaNHA1-n) grew well than yeast strains expressing PhaNHA1 from salt-sensitive reed plants (PhaNHA1-u) in the presence of 100mM NaCl. Furthermore, Na(+) contents of yeast cells expressing PhaNHA1-n were less than half of those of yeast cells expressing PhaNHA1-u. These results suggest that PhaNHA1-n is more efficient at excluding Na(+) from the cells than PhaNHA1-u.     

Up-regulation of glutathione metabolism and changes in redox status involved in adaptation of reed (Phragmites communis) ecotypes to drought-prone and saline habitats

The glutathione (GSH) metabolic characteristics and redox balance in three ecotypes of reed (Phragmites communis), swamp reed (SR), dune reed (DR), and heavy salt meadow reed (HSMR), from different habitats in desert regions of northwest China were investigated. The DR possessed the highest rate of GSH biosynthesis and metabolism with the lowest levels of total and reduced GSH and its biosynthetic precursors, gamma-glutamylcysteine (gamma-EC) and cysteine (Cys), of the three reed ecotypes. This suggests that a higher rate of GSH biosynthesis and metabolism, but not GSH accumulation, might be involved in the adaptation of this terrestrial reed ecotype to its dry habitat. The HSMR shared this profile although it exhibited the highest reduced thiol levels of the three ecotypes. Two key enzymes in the Calvin-cycle possessing exposed sulfhydryl groups, NADP(+)-dependent glyceraldehydes-3-phosphate dehydrogenase (G3PD) and fructose-1,6-bisphosphatase (FBPase), and other two key enzymes in the pentose-phosphate pathway (PPP), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6-PGD), had very similar activities in the three reed ecotypes. Compared to the SR, the DR and HSMR had higher ratios of NADPH/NADP+ and NADH/NAD+, indicating that a more reduced redox status in the plant cells might be involved in the survival and adaptation of the two terrestrial reed ecotypes to long-term drought and salinity, respectively. These results suggest that changes of GSH metabolism and redox balance were important components of the adaptation of reed, a hydrophilic plant, to more extreme dune and saline habitats. The coordinated up-regulations of the rate of GSH biosynthesis and metabolism and reduction state of redox status of plant cells, conferred on the plant high resistance or tolerance to long-term drought and salinity.