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| 沙冬青和胡杨逆境适应的光合及抗氧化机理研究 | |
| 其他题名 | Studies on the adaptive mechanisms of desert plants |
| 李文瑞 | |
| 出版年 | 2002 |
| 学位类型 | 博士 |
| 导师 | 刘新民 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 本文以生长于腾格里沙漠东南缘沙坡头地区的沙冬青和胡杨等荒漠植物为实验材料，从气体交换特性，叶绿素荧光特征以及光合相关基因的表达调节等方面研究了荒漠植物逆境适应的机制。本研究表明气孔限制因子和非气孔限制因子不仅影响了自然生境和灌溉条件下沙冬青的光合同化速率，而且还影响沙冬青的光合同化速率的季节性变化。与灌溉地的沙冬青相比较，在自然生境下沙冬青的光系统n反应中心Dl蛋白，光系统I反应中心PsaA/B蛋白，捕光色素蛋白II（LHCll）和捕光色素蛋白I（LHCI）的含量都降低。采用RNA杂交技术（Northern Blot）进一步研究编码D1蛋白的psbA基因和LHCn的cab基因的表达发现叶绿体PsbA基因的转录水平在两种不同生境的沙冬青基本一致；而核基因编码的cab基因的转录水平在自然生境下的沙冬青较低。这些结果表明在胁迫下核基因编码的叶绿体蛋白的基因的调节主要发生在转录水平，而叶绿体编码的psbA基因表达的调节主要发生在转录后水平。生长在沙漠气候下的河岸林生境的胡杨具有叶形的多样性。本文研究了胡杨披针形叶和圆形叶的净光合同化速率和光系统II光化学反应效率的日变化，发现可能由于高光强、高温和水分胁迫等外在环境胁迫等条件下在中午13：00h时胡杨圆形叶发生严重的光合午休现象，而披针形叶没有发生光合午休现象。与此相反在中午13：00h时胡杨披针形叶的净光合同化速率达到最高。尽管在13：00h时胡杨圆形叶的非光化学反应淬灭与披针形叶相比急剧增加，但所吸收的过量的激发能不能有效地耗散掉而发生了光抑制。免疫印迹显示光系统n反应中心Dl蛋白和捕光色素蛋白n在中午光合午休时都降低。同时由于胡杨圆形叶在13:00h时的低的气孔导度，因而气孔因素和非气孔因素决定了胡杨圆形叶的光合午休。进一步分析胡杨的活性氧的累积和抗氧化酶活的变化表明胡杨圆形叶比披针形叶经受更严重的环境胁迫。本文的研究发现尽管圆形叶发生光合午休，胡杨整体光合效率在整个生长季节能保持在较高的水平，这样就能使荒漠植物能在极端逆境下得以生存并能达到最大的生长速度和生长量。因此，成熟的胡杨同一植株的不同形态的叶形的存在，可能提供了一种适应逆境的保护机制从而使之维持高的生长速度和生长量以适应荒漠气候的胁迫。因此，本研究表明，植物对沙漠逆境的适应除了通常认为的形态解剖上的调节，也存在基因水平和生理生化水平上的调节。多种逆境适应调节的综合应用才使得沙漠植物在沙漠极端逆境下得以正常生长发育。 |
| 英文摘要 | The adaptation of desert plants, Ammopiptanthus mongolicus and Populus euphratica, to environmental stresses were analysed in this study. Two habitats of Ammopiptanthus mongolicus growing in the desert regions of northwest China with (IR) or without watering (DR) were simultaneously investigated for the measurements of gas exchange patterns and the expression of photosynthetic genes. Stomatal conductance and intracellular CO_2 concentration were markedly lower in Ammopiptanthus mongolicus in natural desert habitat (DR) compared to in IR, which may account for the observed depression of net photosynthetic CO2 assimilation rate (Pn) in DR. The steady-state levels of photosystem II (PS II) reaction center protein Dl, light harvesting complex II (LHCII), photosystem I (PS I) reaction center protein PsaA/B and light harvesting complex I (LHC I) were reduced in DR as compared to in IR. Our results indicate that both stomatal and non-stomatal factors contribute to the low carbon assimilation rate in DR. The cab transcripts for nuclear-encoded LHC II were decreased in DR compared with that in IR, while the psbA transcripts for chloroplast-encoded D1 protein remain largely unchanged between in DR and in IR. These results indicate that nuclear-encoded photosynthetic gene is regulated at least at the transcriptional level and that chloroplast-encoded gene is regulated mainly posttranscriptionally.Populus euphratica, with distinct leaf shape polymorphism, grows within a typical desert Tugayi environment. The photosynthetic CO_2 assimilation rate in lanceolate leaves(LL), located at the bottom of the tree's canopy, is dependent on the diurnal changes in irradiation and reaches maximal at 13:00 h, while a severe midday depression was observed in broad-ovate leaves (BOL) at the top of the tree's canopy at 13:00 h, most probably due to high temperature, irradiance and water deficit. Though non-photochemical quenching increased dramatically at 13:00 h in BOL, the photosystem II photochemical efficiency decreased. Western blot analysis showed that both the photosystem II reaction center Dl protein and light harvesting complex II protein were decreased when midday depression occurred in BOL, which suggests that the decreased photosystem II proteins may account for the photosynthetic depression. Together with the observed low stomatal conductance, both stomatal and non-stomatal factors contribute to the midday depression in BOL. Analysis of the accumulation of ROS and the increased antioxidant enzymatic activities further indicated that BOL leaves experienced more severe environmental stresses than LL. From our results, a high level of photosynthetic capacity is maintained through the growth season though a severe midday depression in BOL, which enables the plant to survive the extreme stresses. We suggest that the differently shaped leaves within a single desert tree may provide an adaptive mechanism to the extreme stresses and ensure the maximal growth and productivity. |
| 中文关键词 | 胡杨 ; 沙冬青 ; 光合基因表达 ; 荒漠植物 ; 环境胁迫 ; 光系统II ; 活性氧 ; 气体交换 ; 净光合同化速率 |
| 英文关键词 | Ammopiptanthus mongolicus desert plant environmental stress gas exchange net photosynthetic assimilation rate photosynthetic gene expression PS II Populns euphratica ROS |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286293 |
| 推荐引用方式 GB/T 7714 | 李文瑞. 沙冬青和胡杨逆境适应的光合及抗氧化机理研究[D]. 中国科学院寒区旱区环境与工程研究所,2002. |
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