【作者】 李强；

【导师】 袁道先； 余龙江；

【作者基本信息】 华中科技大学 ， 生物化学与分子生物学， 2007， 博士

【摘要】 国家为修复和保护脆弱的西南岩溶生态环境,多次开展岩溶生态重建示范工程,并在不少地区把忍冬属植物(俗称金银花)作为重要先锋植物进行推广,来扼制石漠化趋势,以实现石漠化生态治理与建设和金银花产业的持续性发展。关于忍冬属植物在岩溶环境中的适应机制研究一直滞后于国家发展目标。本文通过野外观测和室内栽培实验相结合的方式来研究生长在广西弄拉岩溶观测站中的忍冬属植物的生物地球化学特征,来探讨其对岩溶环境的适应机制,进而为研究岩溶植物适生机制和发展金银花产业提供理论支撑。本文研究结果表明:1)研究区石灰土壤的不同层次,土壤元素有效态和有效率顺序基本为Ca>Mg>Cu>Mn>K>Na>P>B>SiO2>Zn>Fe。因生长在该区的两种忍冬属植物受生境生物地球化学特征的影响,其叶细胞中的元素含量均表现出Ca多Mg少(相关系数-0.056,P<0.05),并且P在叶细胞内的含量仅次于Ca的现象(相关系数0.868,P<0.01)。在蒸腾拉力作用下进入忍冬属植物体内的钙不但通过积累效应造成Ca在叶细胞中含量较高,与土壤中该元素的含量呈现出正相关性,而且还通过元素间的拮抗作用或协同作用影响其它元素在植物叶细胞内的含量,进而影响忍冬属植物的质量及有效成分的积累。由于钙元素在植物体内过多积累会干扰其磷酸代谢体系,因此,忍冬属植物为解除钙盐毒害,通过叶上的泌钙腺体来排除体内多余的钙以适应岩溶环境。2)忍冬属植物为适应岩溶干旱环境,其叶在形态结构上表观出一系列旱生植物结构特点。研究表明:上表皮具有众多的沟槽状凹陷结构,该结构的存在使植物与外界水分交换速率减慢。气孔仅存在下表皮,气孔密度高达328个/mm2以上,并被茂密的表皮毛所遮挡,小而数目众多的气孔能够使忍冬属植物保持高光合速率,而光合速率的提高是其抵抗干旱的重要因素之一,而且还能在水分紧张时抑制蒸腾作用;茂密的表皮毛则能使植物的气孔处于一个相对密闭的环境,进而抑制蒸腾速率。此外,忍冬属植物具有的异面叶和发达的机械组织可以提高水分输送效率。3)通过盆栽实验研究了忍冬属植物在添加15 mmol/L和30 mmol/L CaCl2后在光合生理生化上对岩溶干旱作出的响应机制。结果表明在岩溶干旱过程中,忍冬属植物通过利用土壤中的钙来抑制气孔导度、减慢蒸腾速率以及提高水分利用效率和光合速率来适应岩溶干旱环境。在外源钙浓度为15 mmol/L时忍冬属植物的光合作用均能得到显著提高,而过高的外源钙则对部分忍冬属植物造成伤害。外源钙浓度为15 mmol/L时,忍冬属植物光合速率增速结果为:华南忍冬>忍冬>灰毡忍冬>蒙花二号>蒙花一号>金银花。忍冬属植物在此时的光合生理特征与其叶绿素升幅、脯氨酸含量、CAT活性提高强度上具有正相关性,而与可溶性糖、丙二醛含量成负相关性,从而说明其在抵御岩溶干旱能力上的差异。通过该实验可以看出岩溶土壤钙离子的存在能够增加忍冬属植物干旱抵御能力,进而适应岩溶环境。4)通过激光共聚焦显微镜成像技术,进一步认识到维持忍冬属植物生命活动的钙离子在其细胞内分布状况以及钙元素过多时的腺体分泌方式。钙离子主要分布在叶绿体上,与植物光系统II ( PS II)上存在许多钙结合位点以及Ca2+是PS II功能表达的必需协同因子相关;而钙离子腺体的存在通过调节渗透平衡,提高其抗旱性。该结果可以说明岩溶区植物为适应干旱、强光环境而具有光合速率高、生物量大特点,以及岩溶区适宜种植利用茎、叶为目的的植物。5)通过聚类分析和遗传距离对比发现本文所选用的材料具有丰富遗传多样性,能够代表不同区域环境特征。而钙调素基因的差异则影响其对岩溶环境的适应能力。综上所述,生长在岩溶区的忍冬属植物为适应岩溶干旱环境不但在形态上具有一定的适应特征,而且还能通过调节渗透压、改变光合速率、维持叶绿体质膜系统和结构的稳定以及提高酶保护系统活性。而上述一系列岩溶逆境适应机制是在以Ca-CAM为核心的信号转导过程中实现的。更多还原

【Abstract】 The karst system in southwestern China is fragile and has the special particularities, such as calcium-rich and water leakage. Rock desertification occurs there under the impact of anthropogenic activities. In order to harness the rock desertification at karst area in southwest China, our government carried out many rehabilitation projects and called on the local people to plant perennial Flos Lonicerae. Perennial Flos Lonicerae is not only adaptable to karst environment, but also can be as medical herb due to its flower containing many kinds of officinal ingredients. In the past, many distinguished rehabilitation results are got, but the relationship between Flos Lonicerae and the karst environment and the ecology adaptation character of Flos Lonicerae is not clear due to lack of experimental data. Then, Flos Lonicerae is selected as intermedia in this paper to research the mechanism of cross-adaptation to water stress in plants at karst area in southwestern China and understand the structural and functional responses of plant to environmental stress. The research mainly includes the relationship between the elements character of Flos Lonicerae and the karst biogeochemistry, the drought-resistant mechanisms of Flos Lonicerae on their leaf-structure, the photosynthetic physiological ecology of Flos Lonicerae, the distribution character of Ca2+ in the cell of Flos Lonicerae and the modulation of calcium.1) In order to study the characteristics of element values in the cell of plants and soils and their relationship, which to evaluate the biogeochemical effect of soil on the element contents in the cells of plants in the same environment of southwestern China, the soil samples were collected for analysis and the weight and atom percent of elements (WT% and AT%) in the leaves of two different species of Flos Lonicerae was analyzed by the electron probe. From the results of soil analysis, it can be seen that though the total element values in soil of different layers were arranged in SiO2>Fe>Ca>Mg>K>Na>Mn>P>Zn>B>Cu, the nutrient element contents in the soil were determined by the liable content of elements, which were arranged in Ca>Mg>Cu>Mn> K>Na> P>B>SiO2> Zn>Fe. That is to say, the karst environment is composed of soluble rock, soil scarcity and calcium-rich. Moreover, the migratory velocity and availability of elements were also determined by their coefficient variability. According to statistical results, Ca, Mn and P in the soil have high coefficient variability, which reflects its background of karst soil. The content of Ca is higher while the content of Mg is lowest in the cell of two different species of Flos Lonicerae (r=-0.156,P<0.05) and the content of P in the cell is inferior to Ca (r=0.868,P<0.01). By studying the relationship of soil and the plants, it can be seen that the above result perhaps is caused by the character of local biogeochemistry. Ca is mainly absorbed by plant with the help of transpiration and accumulated in the cell, which becomes the highest element in the cell. Under the accumulation of Ca in cell of plant, it will affect the absorbency and the content of other elements in the cell of Flos Lonicerae. As a result, the content of other elements in the Flos Lonicerae appears different by synergistic action and antagonistic action, which affects its quality and officinal value.2) The leaf epidermis of Lonicera japonica Thunb. and Lonicera confusa in the genus of Flos Lonicerae were mainly observed by scanning electron microscopes (SEM) to study the characteristics of stomata, trichomes and dermal cell, etc.. The results showed that stoma exists only on the lower epidermis and its distribution is irregular, and leaf epidermis consist of epidermis cells, stoma complexes and bushy trichomes including glandular hair and non-glandular hair. On the upper epidermis, anticlinal wall caves in sinuous groove to countercheck the transpiration. Evidences from leaf morphological structures serve as another proof on drought-resistant mechanisms. Some strumaes distributing regularly are hypothesized as oxalic calcium on the lower epidermis under laser scanning confocal microscopy (LSCM) with Fluo-3/AM, which can increase their endurance to drought stress. Therefore, the above characteristics of Flos Lonicerae can reduce the loss of water and make Japanese honeysuckle and Wild Honeysuckle adapt to the droughty environment at karst area in southwest China. However, there are some differences of the two species.3) During the drought stress and the rewatering process, Flos Lonicerae can increase the content of MDA, proline, soluble sugar and chlorophyll and improve the activity of peroxide enzyme. With the soil losing water, the modulation of Flos Lonicerae decreases. However, when soil pre-treatment with the suitable Ca2+ concentration (about 15mmol/L) during drought stress could increase peroxide enzyme activity and soluble sugar content,alleviate cell membrane leakage and chlorophyll decomposition.Then , Flos Lonicerae have the low transpiration and high photosynthesis at this kind of soil pre-treatment, which shows the positive correlation with the chlorophyll, proline content and the activity of peroxide enzyme and the negative correlation with MDA, soluble sugar contents.4) By studying the distribution of Ca2+ in the cell of Flos Lonicerae, it can be seen that Ca2+ mainly appears in chlorophyll pigments and connects with PS II, which can explain the plant at karst area with high photosynthesis characters.5) By analysis the genetic relationship between the genotypes of Flos Lonicerae and their relatives based on RAPD distances, it can be seen that the experimental plants can stand by their original environment. Moreover, by comparing the cDNA of CaM from Flos Lonicerae, it shows that the difference of CaM leads to their different acclimation.From the above results , it can be seen that in order to adapt the karst environment, Flos Lonicerae have the drought leaf-structure, the high photosynthetic physiological character and the osmotic modulation, which can adjust by the Ca-CaM.更多还原