【作者】 赵燕；

【导师】 李悦； 孔范龙；

【作者基本信息】 青岛大学 ， 环境科学与工程， 2022， 硕士

【摘要】 互花米草是一种高度入侵的植物,其在全球范围内的蔓延已对许多国家沿海地区的生态系统安全和经济发展造成了严重的威胁。由于互花米草生长在沿海滩涂,进行机械施工的难度大,加上其本身根系发达、抗逆性强、恢复速度快等特点,现存处理方法成本高、起效慢,短期内难以完全清除互花米草,同时易引发环境污染和二次入侵等问题。生物防治,特别是植物的化感抑制作用,作为一种环保有效的方法为防治互花米草的入侵提供了一种新的思路。已有的研究证明浒苔能分泌对其他物种具有抑制作用的化感物质。利用浒苔防治互花米草,既能控制互花米草的蔓延,又能实现浒苔的资源化利用。本文通过室内控制实验研究了不同溶剂制备的浒苔浸提液对互花米草种子萌发和幼苗生长的化感抑制作用及抑制机理,并利用聚乙烯醇（PVA）/海藻酸钠（SA）水凝胶包埋浒苔浸提液制备了缓释剂,通过人工湿地反应器小试实验考察其对互花米草幼苗生长的抑制效果。主要研究结果如下:（1）浒苔浸提液对互花米草种子萌发和幼苗生理指标的影响三种不同处理（水、甲醇和乙酸乙酯）的浒苔浸提液均能降低互花米草种子的萌发率和萌发指数,降低幼苗的苗长和根长,影响植物体内超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）等抗氧化酶的活性及丙二醛（MDA）、脯氨酸（Pro）等渗透调节物质的含量,导致互花米草的抗氧化系统和细胞的渗透平衡遭到破坏,从而抑制互花米草的生长。浸提液浓度越高,抑制效果越好。其中,浒苔水浸提液对互花米草的抑制效果最好,当水浸提液浓度达到0.20 g·m L^-1时,互花米草种子的萌发率降至对照组的49.53%,幼苗的鲜重和干重分别降低了13.73%和9.53%,SOD、CAT的活性分别降低了74.74%和45.49%,根系活力降低了80.58%。（2）浒苔浸提液影响下互花米草的差异表达基因（DEGs）分析为了研究添加浒苔浸提液后互花米草在基因水平的变化,对其转录组测序结果进行分析。结果表明,添加浒苔浸提液后,互花米草的转录因子在MYB superfamily、AP2/ERF、C2C2和NAC等与胁迫相关的家族显著富集;与氨基酸代谢和光合作用相关的基因表达上调,与能量生成和代谢相关的基因表达下调;差异表达基因在“核糖体”、“光合生物中的碳固定”、“光合作用天线蛋白”等途径富集。说明浒苔浸提液的胁迫影响了互花米草的正常生理功能。（3）浒苔浸提液中主要化感物质分析通过GC-MS对浒苔浸提液进行组分分析,发现提取物中富含对植物生长有抑制作用的有机酸、醇和酯。其中Valine等可以抑制其他藻类和浮游植物的生长,并造成植物的连作障碍;Butanoic acid,butyl ester和Hexanedioic acid,bis（2-ethylhexyl）ester等能导致细胞内活性氧自由基的过度积累及叶绿素a的含量降低,最终导致植物细胞死亡。因此,浒苔浸提液中测得的上述物质可能是抑制互花米草生长、降低植株生物量的主要化感物质。（4）PVA/SA水凝胶缓释剂对互花米草生长的影响为了便于实际应用,采用聚乙烯醇/海藻酸钠水凝胶包埋浒苔水浸提液制备缓释剂。在反应器中投加缓释剂后互花米草幼苗的生物量和光合作用等受到不同程度的影响。实验结果表明,随着盐度的增加互花米草幼苗的存活率、鲜重与叶绿素b的含量先降低后升高又迅速降低,幼苗的干重与叶绿素a的含量先升高后降低。当盐度增加到30 ppt后,互花米草的叶绿素含量和干物质占比迅速下降,存活率仅为21.67%。实验结果表明利用浒苔制备的缓释剂可以抑制互花米草的生长,为控制互花米草的蔓延、实现浒苔的资源化利用提供了一种可行的方法。更多还原

【Abstract】 Spartina alterniflora（S.alterniflora）,a highly invasive plant,has caused a serious threat to ecosystem biodiversity and economic development in coastal areas of many countries.As S.alterniflora grows in coastal beach,it is difficult to carry out mechanical construction.In addition,due to the well-developed root system,strong stress resistance,fast recovery and other factors of S.alterniflora,the existing control methods have a lot of disadvantages,such as high cost and slow effect.In addition,it is difficult to completely remove S.alterniflora in a short time,and easy to cause environmental pollution and secondary invasion.Biological control,especially the allelopathy inhibition of plants,provides a new idea for controlling the invasion of S.alterniflora as an environmental and effective method.Previous studies have proved that Ulva prolifera（U.prolifera）could secrete allelochemicals to inhibit other species.The use of U.prolifera to control S.alterniflora can not only control the spread of S.alterniflora,but also realize the resource utilization of U.prolifera.In this paper,the allelopathic effects and inhibition mechanism of U.prolifera extracts on the seed germination and seedling growth of S.alterniflora were studied by laboratory control experiment.The sustained-release agent was prepared by embedding U.prolifera extract with polyvinyl alcohol（PVA）/sodium alginate（SA）hydrogel,and its inhibition effects on seedling growth of S.alterniflora were explored in constructed wetland reactors.The main research results are as follows:（1）Effects of U.prolifera extract on seed germination and seedling physiological indexes of S.alternifloraThree different treatments（aqueous,methanol and ethyl acetate extracts）could inhibit the seed germination and seedling growth of S.alterniflora by reducing the germination percentage and germination index of seeds,decreasing the seedling length and root length of seedlings.At the same time,U.prolifera extract would affect the activities of superoxide dismutase（SOD）,catalase（CAT）and peroxidase（POD）and the contents of malondialdehyde（MDA）and proline（Pro）,resulting in the destruction of the antioxidant system and cell osmotic balance of S.alterniflora.The higher the concentration of extract,the higher the inhibition effect.Among them,the aqueous extract of U.prolifera had the best inhibitory effect on S.alterniflora.When the concentration of aqueous extract reached0.20 g·m L^-1,the germination percentage of S.alterniflora decreased to 49.53%of the control,the fresh weight and dry weight of seedlings decreased by 13.73%and 9.53%respectively,the activities of SOD and CAT decreased by 74.74%and 45.49%respectively,and the root activity decreased by 80.58%.（2）Analysis of differentially expressed genes（DEGs）of S.alterniflora after adding U.prolifera extractIn order to study the changes of S.alterniflora at the gene level after adding U.prolifera extract,transcriptome sequencing results were analyzed.The results showed that the transcription factors of S.alterniflora were enriched in MYB superfamily,AP2/ERF,C2C2,NAC and other families after adding U.prolifera extract.The expression of genes related to amino acid metabolism and photosynthesis were upregulated,while the expression of genes related to energy generation and metabolism were downregulated.The DEGs are enriched in“ribosomes”,“carbon fixation in photosynthetic organisms”,“photosynthetic antenna proteins”and other pathways.The results showed that the stress of U.prolifera extract affected the normal physiological function of S.alterniflora.（3）Analysis of allelochemicals in U.prolifera extractThe components of U.prolifera extract were analyzed by GC-MS.It was found that the extract was rich in organic acids,alcohols and esters that could inhibit the growth of plants.Among them,Valine could inhibit the growth of other algae and phytoplankton,resulting in the obstacle of continuous cropping of plants;Butanoic acid,butyl ester and Hexanedioic acid,bis（2-ethylhexyl）ester could lead to the excessive accumulation of reactive oxyradical and the decrease of chlorophyll a,and finally lead to cell death of plant.Therefore,the above substances measured in U.prolifera extract could be the main allelochemicals that inhibit the growth and reduce the plant biomass of S.alterniflora.（4）Effects of PVA/SA hydrogel sustained-release agent on the growth of S.alternifloraIn order to facilitate the practical application,PVA/SA hydrogel was used to embed U,prolifera extract and prepare sustained-release agent.After addition,the biomass and photosynthesis of S.alterniflora in the reactor were affected to varying degrees.The results showed that with the increase of salinity,the survival rate,fresh weight and chlorophyll b content of S.alterniflora first decreased,then increased and then decreased rapidly,while the dry weight and chlorophyll a content of seedlings increased first and then decreased.When the salinity increased to 30 ppt,the content of chlorophyll and the proportion of dry weight of S.alterniflora decreased rapidly,and the survival rate was only 21.67%.The results showed that the sustained-release agent prepared by U.prolifera could inhibit the growth of S.alterniflora,which provided a feasible method for controlling the invasion of S.alterniflora and realizing the resource utilization of U.prolifera.更多还原