【作者】 陈婷；

【导师】 曾波；

【作者基本信息】 西南大学 ， 生态学， 2007， 硕士

【摘要】 在湿地环境下，由于土壤积水导致了一系列的反应，所当其冲就是土壤氧化电势的下降。在这种低氧化电势的条件下，耐水淹植物采取了一系列的措施度过不良环境，其中包括了体内通气组织的形成和形成不定根。通气组织通常形成于耐水淹植物的根、节结、根状茎、茎及被水淹过的叶片中。通气组织的形成可以减小氧气从植物茎向根部的运输阻力，供给根部正常的呼吸作用所需要的氧气。通气组织可分为两种类型：裂生性通气组织和溶生性通气组织。裂生性通气组织是植物体内成熟细胞经过一定的方式分离和扩展后形成的；溶生性通气组织则是由一些细胞死亡溶解后形成的空洞。不过，这两种类型的通气组织在同一种植物体内可同时存在；在同一器官中，裂生性通气组织早于溶生性通气组织形成。野古草(Arundinella anomala Steud．)和秋华柳(Salix variegata Franch．)是长期生长在三峡库区消落区的两种植物。本文通过徒手切片法获取该两物种(成年植株和幼苗)茎横切片，研究在不同水淹条件下，其茎通气组织变化情况，并同时分析了两物种(成年植株)的不定根生长情况，从而了解野古草和秋华柳一定的耐水淹机制。我们还通过无水淹条件下激素溶液的施加实验，分析水淹是否是植物茎通气组织形成的直接原因。实验结果如下：(1)连续水淹与间歇水淹处理都能促使野古草成年植株茎通气组织有明显的增加现象。不同的水淹处理对野古草植株茎中通气组织的形成有着不同程度的影响，连续水淹与间歇水淹相比更能促进野古草植株茎通气组织的提前形成。秋华柳成年植株水淹60d后体内未发现通气组织形成现象。(2)不同水淹处理都促进了野古草和秋华柳幼苗茎通气组织的形成。根部水淹环境中的野古草和秋华柳幼苗在5d后茎中通气组织表现出明显的增加现象，全淹条件下的植株也有一定的增长趋势。植株体内通气组织的形成是野古草和秋华柳幼苗度过水淹胁迫环境的策略之一。(3)在无水淹条件下，外施的不同浓度乙烯利和生长素溶液都促进了野古草和秋华柳幼苗茎中通气组织的形成。水淹条件下植物体内通气组织发生与乙烯和生长素含量上升有直接关系，水淹本身并不一定是导致植物体内通气组织发生的直接原因。(4)在连续水淹条件下，野古草不定根的生成早于秋华柳植株。连续根部水淹30d前，野古草植株不定根的生长量随水淹时间的增加而不断增长，30d后，不定根量开始减少；随着连续根部水淹时间的增加，秋华柳不定根生长也有增加的现象。水淹20d后，根部水淹的野古草不定根生长量都明显高于全淹环境中的野古草；全淹环境中的秋华柳植株几乎无不定根的生成，只在全淹60d后一两株秋华柳植株有不定根生长现象。可见不同的水淹时间和水淹方式对秋华柳和野古草不定根的形成有着不同程度的影响。总之，野古草和秋华柳植物体内通气组织的形成在很大程度上减小了氧气在体内的运输阻力，缓解了植株在水淹环境下的缺氧状况；在水淹条件下，野古草和秋华柳不定根的生长也是其适应水淹环境的策略之一，这都促使野古草和秋华柳具有很强的耐水淹能力。更多还原

【Abstract】 In wetlands, soil flooding initiates a chain of reactions leading to reduced soil oxidation-reduction potential （Eh）. Flood-tolerant plants use several strategies to cope With low soil Eh conditions, such as the development of aerenchyma and adventitious roots. The stress brought on by low O₂ concentrations in flooded soils leads to the formation of aerenchyma in tolerant plant species, a process that can occur in roots, nodules, rhizomes, stems and submerged leaves. Aerenchyma is cortical airspaces which provide a low resistance internal pathway for the movement of O₂ from the shoots to the roots, where it is consumed in respiration and may also re-oxidize the rhizosphere.Aerenchyma can be of two types: schizogenous aerenchyma and lysigenous aerenchyma. Cortical aerenchyma may be formed by a specific process of separation and differential expansion of mature cells （schizogenous aerenchyma） or by death and dissolution of such cells （lysigenous aerenchyma）. Nevertheless, both types of aerenchyma can occur in the same plant and schizogenous aerenchyma may precede the occurrence of lysigenous aerenchyma in the same organ.In this paper, we measured aerenchyma of stem of Arundinella anomala Steud. and Salix variegata Franch., shrubs growing in fluctuating zone of The Three Gorges reservoir suffer periodic flooding, in different flooding environments. Meanwhile we analyzed the formation of adventitious roots about them. In order to ascertain whether phytohormone ethylene and auxin are direct stimuli for aerenchyma formation in flooded plants, we investigated the aerenchyma formation in the stem of A. anomala and S. variegata as affected by addition of ethylene and a-naphthalene acetic acid （a-NAA） under non-flooding conditions.Experiment results are as follows:（1） There were obvious increases in the aerenchyma’s areas of adult A. anomala in continuous flooding treatment and intermittent flooding treatment. Different flooding treatments lead to different changes about the aerenchyma’s formation of A. anomala. Compare with intermittent flooding treatment, the formation of aerenchyma of A. anomala plant is earlier promoted by continuous flooding. There was hardly the formation of aerenchyma of S. variegata plant grew up by 60 d flooding treatment.（2） Following different flooding treatments, the aerenchyma areas of the stem of A. anomala and S. variegata seedlings were all increased. After 5 flooding days, the aerenchyma’s area of stem of A. anomala and S. variegata seedlings in belowground submerged treatment was bigger than the control seedlings. There still have increased in the aerenchyma’s area of stem of A. anomala and S. variegata seedlings submerged with 2m water depth. The seedlings can live in anoxic environment by the aerenchyma formation.（3） In the experiment that the aerenchyma formation in the stem of A. anomala and S. variegata was enhanced when plants were irrigated with either ethylene or a-naphthalene acetic acid. Moreover, the aerenchyma formation in the stem of these two species was strengthened with hormone concentration, in flooding environments, the aerenchyma formation in stem of plants has direct relations to the increase of ethylene and auxin in plants, flooding may not be the direct stimulus for the formation of aerenchyma in plants.（4） adventitious rooting formation of A. anomala was earlier than that of S. variegate. Before 30 d belowground submerged, the number of adventitious rooting of A. anomala was straightly increasing. And after 30 d, the status was turning. After belowground submerged for 20 d, the number of adventitious rooting of A. anomala was more than that of A. anomala plants submerged with 2m water depth. The number of adventitious rooting of S. variegate was increasing in belowground submerged treatment. There was almost not adventitious rooting formation of S. variegate plants submerged with 2 m water depth. So different flooding treatments lead to different adventitious rooting formation of A. anomala and S. variegate.In conclusion, A. anomala and S. variegata can form aerenchyma in order to reduce the resistance of transporting oxygen so that the plants can live in anoxic flooding environment. In flooding condition, the formation of adventitious roots of A. anomala and S. variegata plants was increased. A. anomala and S. variegate have great capacity to living in flooding environment by the formation of aerenchyma and adventitious roots.更多还原