过度放牧下高原早熟禾矮小化及其形成机理
发布时间：2018-08-27 09:24
【摘要】：高寒草甸是青藏高原的主体,对维持生态系统功能有重要的作用,长期过度放牧下,高寒草甸主要优势植物高原早熟禾(Poa alpigena)表现出明显的矮小化现象。研究高寒草甸植物矮小化形成机理,为深刻解析高寒草甸退化机理有重要的科学意义。因此,本文以高原早熟禾为研究对象,通过野外放牧试验和室内试验相结合的方法,系统研究了放牧对高原早熟禾个体性状、形态解剖结构、组织器官激素、基因表达的影响,从个体、细胞、分子水平深入研究过度放牧对高原早熟禾矮小化形成机理,主要结论如下:1在长期放牧干扰下,除叶片数外高原早熟禾株高、分枝数、叶片数、叶长、叶宽、叶面积、茎粗、茎长、根长、根粗、穗长、总叶质量、单叶质量、茎重、穗重、根重、全株重等性状均出现显著变小的特征(p0.05);通过构建高原早熟禾性状可塑性变化谱,发现株高、茎长、分蘖数、全株重等可塑性幅度较大,为放牧响应的敏感指标,说明过度放牧下高原早熟禾株高、茎长、个体生物量等性状指标的减小导致了高原早熟禾矮小化的发生;通过高原早熟禾个体生物量与性状指标间相关性分析,株高、叶长、叶宽、叶面积、茎长、穗长、分枝数等性状与个体生物量呈现显著正相关关系(p0.01),说明这些指标的减小是导致高原早熟禾长期放牧下个体生物量降低的主要因子。2通过对放牧和围封下高原早熟禾茎叶解剖结构的研究,结果表明:叶片厚度、表皮角质层、上下表皮细胞面积、韧皮部厚度,随着放牧干扰强度的增加而增大(p0.05);叶肉细胞面积、茎表皮细胞面积、木质部厚度、导管壁厚度随着放牧干扰强度的增加而减小(p0.05),而叶肉细胞密度无显著差异;叶上下表皮细胞面积、上表皮角质层厚度、叶木质部厚度可塑性指数较高,PI均大于0.5。茎导管直径、表皮细胞大小、表皮角质层厚度可塑性指数较高,PI大于0.4;说明在过度放牧下叶片厚度、表皮角质层厚度、韧皮部厚度的增加,是高原早熟禾为了抵御牲畜啃食而采取的防御策略。而过度放牧下叶肉细胞面积、茎表皮细胞面积的减小,而密度无显著变化,说明高原早熟禾叶片和茎杆趋于缩短,进而导致了矮小化的发生。3通过对放牧与围封下高原早熟禾叶肉细胞超微结构特征的研究,结果表明,随着放牧干扰强度的增加,叶肉细胞面积、细胞壁厚、嗜饿颗粒数、叶绿体面积、线粒体数量及线粒体大小逐渐减小(p0.05)。高原早熟禾通过改变叶肉细胞叶绿体和线粒体的结构和大小来响应放牧胁迫,由此推断叶绿体和线粒体结构和大小的改变可能是高原早熟禾矮小化形成的细胞学机制。4通过对放牧和围封下高原早熟禾内源激素油菜素内酯(GA3)、生长素(IAA)、赤霉素(BR),以及丙二醛(MDA)和超氧化物歧化酶(SOD)的分析发现,过度放牧下高原早熟禾根部BR、IAA、GA3含量显著高于围封条件下(p0.05),说明过度放牧下,三种激素主要提供地下部分的生长,这是对放牧胁迫所采取的繁殖分配策略;茎中BR、IAA含量放牧与围封无显著差异(p0.05),而GA3含量过度放牧显著小于围封(p0.05),叶中BR、IAA、GA3含量随着放牧干扰的增加而减小(p0.05),GA3的主要功能是促进茎的伸长,由此说明过度放牧下GA3含量的减小可能是高原早熟禾矮小化形成的主要生理响应机制;高原早熟禾SOD和MDA含量随着放牧干扰的增加而增加(p0.05),说明在过度放牧胁迫下茎叶中MDA含量积累,膜脂氧化程度加剧,在清除放牧胁迫所积累的自由基过程中SOD起重要作用。5采用HiSeqTM 2500高通量测序技术对高原早熟禾矮小化植株和正常植株基因表达进行了转录组测序,并对测得序列进行了组装、功能注释、分类和代谢通路分析。结果表明,组装后共获得181,304条Unigene,组装完整性较高;对Unigene进行功能注释,共获得109,136条Unigene的注释结果,识别差异表达基因15615条;GO差异表达基因富集分析表明,生物学进程中,响应刺激类富集基因差异显著;细胞组分中,叶绿体富集基因差异表达显著;分子功能中,氧化还原酶活性类富集基因差异表达显著;KEGG差异表达基因富集注释结果显示,代谢通路上差异表达基因富集注释最多,进一步对各通路进行Pathway富集分析和筛选,最后筛选出富集差异显著的通路有光合作用途径、叶绿体光合代谢、氧化磷酸化、蛋白酶、过氧化物酶、脂肪酸降解、Notch信号途径等7富集差异通路。说明在放牧胁迫下高原早熟禾经历了复杂的生理过程,通过这类功能基因的调整来适应放牧胁迫。
[Abstract]:Alpine meadow is the main part of Qinghai-Tibet Plateau and plays an important role in maintaining ecosystem function. Poa alpigena, the dominant plant in alpine meadow, shows obvious dwarfing phenomenon under long-term overgrazing. In this paper, the effects of grazing on individual traits, morphological and anatomical structures, hormones in tissues and organs, and gene expression of Poa pratensis were systematically studied by combining field grazing experiment with laboratory experiment. The effects of Overgrazing on individual, cellular and molecular levels of Poa pratensis were studied. The main conclusions are as follows: 1. Under the disturbance of long-term grazing, plant height, branch number, leaf number, leaf length, leaf width, leaf area, stem diameter, stem length, root length, root thickness, spike length, total leaf weight, single leaf weight, stem weight, spike weight, root weight, whole plant weight and other traits of Poa pratensis were significantly reduced (p0.05). The plasticity of plant height, stem length, tiller number and whole plant weight were found to be the sensitive indexes of grazing response, indicating that the reduction of plant height, stem length and individual biomass under overgrazing led to the dwarfing of Poa pratensis. Correlation analysis showed that plant height, leaf length, leaf width, leaf area, stem length, spike length, branching number and other traits had significant positive correlation with individual biomass (p0.01), indicating that the reduction of these indicators was the main factor leading to the reduction of individual biomass under long-term grazing of Poa pratensis. The results showed that the leaf thickness, epidermal cuticle, upper and lower epidermal cell area, phloem thickness increased with the increase of grazing disturbance intensity (p0.05); mesophyll cell area, stem epidermal cell area, xylem thickness, vessel wall thickness decreased with the increase of grazing disturbance intensity (p0.05), while mesophyll fine. There was no significant difference in cell density; the area of upper and lower epidermis cells, the thickness of upper epidermis cuticle, and the plasticity index of xylem thickness were higher than 0.5. The diameter of stem vessel, the size of epidermis cells, and the plasticity index of epidermis cuticle thickness were higher than 0.4 under overgrazing. However, under overgrazing, the area of mesophyll cells and the area of stem epidermis cells decreased, while the density did not change significantly. This indicated that the leaf and stem tended to shorten, which led to the occurrence of dwarfing. 3. The results showed that with the increase of grazing disturbance intensity, mesophyll cell area, cell wall thickness, starvation granule number, chloroplast area, mitochondria number and mitochondria size gradually decreased (p0.05). Poa pratensis responded to grazing stress by changing the structure and size of chloroplast and mitochondria in mesophyll cells. It is concluded that the changes of chloroplast and mitochondria structure and size may be the cytological mechanism of dwarfing in Poa pratensis. 4 By analyzing the endogenous hormones of Brassinolide (GA3), Auxin (IAA), Gibberellin (BR), Malondialdehyde (MDA) and Superoxide Dismutase (SOD) in Poa pratensis under grazing and enclosure, it was found that overgrazing and overgrazing were the main causes of dwarfing. The contents of BR, IAA and GA3 in the roots of Poa pratensis under grazing were significantly higher than those under enclosure (p0.05), indicating that the growth of underground parts was mainly provided by the three hormones under overgrazing, which was a reproductive allocation strategy for grazing stress; there was no significant difference between grazing and enclosure in the contents of BR and IAA in stems (p0.05), but the content of GA3 was significantly lower under overgrazing than that under enclosure (p0.05). The content of BR, IAA and GA3 in leaves decreased with the increase of grazing disturbance (p0.05). The main function of GA3 was to promote stem elongation, which indicated that the decrease of GA3 content under overgrazing might be the main physiological response mechanism of dwarfing formation of Poa pratensis. The content of SOD and MDA in Poa pratensis increased with the increase of grazing disturbance (p0.05). The results showed that MDA accumulation in stems and leaves and membrane lipid oxidation intensified under overgrazing stress, and SOD played an important role in clearing free radicals accumulated under grazing stress. The assembly, functional annotation, classification and metabolic pathway analysis showed that 181,304 Unigenes were obtained after assembly, and the assembly integrity was high; 109,136 Unigenes were obtained by functional annotation, and 15615 differentially expressed genes were identified; the enrichment analysis of GO differentially expressed genes showed that the response stimuli were in the biological process. There were significant differences in enrichment genes; chloroplast enrichment genes were significantly differentially expressed in cell components; oxidoreductase enrichment genes were significantly differentially expressed in molecular functions; KEGG differentially expressed genes were enriched and annotated most frequently in metabolic pathways, and Pathway enrichment analysis was carried out for each pathway. Finally, seven pathways with significant enrichment differences were screened out, including photosynthesis pathway, chloroplast photosynthesis metabolism, oxidative phosphorylation, protease, peroxidase, fatty acid degradation, Notch signaling pathway and so on. To adapt to grazing stress.
【学位授予单位】：甘肃农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S812.8
本文编号：2206842
[Abstract]:Alpine meadow is the main part of Qinghai-Tibet Plateau and plays an important role in maintaining ecosystem function. Poa alpigena, the dominant plant in alpine meadow, shows obvious dwarfing phenomenon under long-term overgrazing. In this paper, the effects of grazing on individual traits, morphological and anatomical structures, hormones in tissues and organs, and gene expression of Poa pratensis were systematically studied by combining field grazing experiment with laboratory experiment. The effects of Overgrazing on individual, cellular and molecular levels of Poa pratensis were studied. The main conclusions are as follows: 1. Under the disturbance of long-term grazing, plant height, branch number, leaf number, leaf length, leaf width, leaf area, stem diameter, stem length, root length, root thickness, spike length, total leaf weight, single leaf weight, stem weight, spike weight, root weight, whole plant weight and other traits of Poa pratensis were significantly reduced (p0.05). The plasticity of plant height, stem length, tiller number and whole plant weight were found to be the sensitive indexes of grazing response, indicating that the reduction of plant height, stem length and individual biomass under overgrazing led to the dwarfing of Poa pratensis. Correlation analysis showed that plant height, leaf length, leaf width, leaf area, stem length, spike length, branching number and other traits had significant positive correlation with individual biomass (p0.01), indicating that the reduction of these indicators was the main factor leading to the reduction of individual biomass under long-term grazing of Poa pratensis. The results showed that the leaf thickness, epidermal cuticle, upper and lower epidermal cell area, phloem thickness increased with the increase of grazing disturbance intensity (p0.05); mesophyll cell area, stem epidermal cell area, xylem thickness, vessel wall thickness decreased with the increase of grazing disturbance intensity (p0.05), while mesophyll fine. There was no significant difference in cell density; the area of upper and lower epidermis cells, the thickness of upper epidermis cuticle, and the plasticity index of xylem thickness were higher than 0.5. The diameter of stem vessel, the size of epidermis cells, and the plasticity index of epidermis cuticle thickness were higher than 0.4 under overgrazing. However, under overgrazing, the area of mesophyll cells and the area of stem epidermis cells decreased, while the density did not change significantly. This indicated that the leaf and stem tended to shorten, which led to the occurrence of dwarfing. 3. The results showed that with the increase of grazing disturbance intensity, mesophyll cell area, cell wall thickness, starvation granule number, chloroplast area, mitochondria number and mitochondria size gradually decreased (p0.05). Poa pratensis responded to grazing stress by changing the structure and size of chloroplast and mitochondria in mesophyll cells. It is concluded that the changes of chloroplast and mitochondria structure and size may be the cytological mechanism of dwarfing in Poa pratensis. 4 By analyzing the endogenous hormones of Brassinolide (GA3), Auxin (IAA), Gibberellin (BR), Malondialdehyde (MDA) and Superoxide Dismutase (SOD) in Poa pratensis under grazing and enclosure, it was found that overgrazing and overgrazing were the main causes of dwarfing. The contents of BR, IAA and GA3 in the roots of Poa pratensis under grazing were significantly higher than those under enclosure (p0.05), indicating that the growth of underground parts was mainly provided by the three hormones under overgrazing, which was a reproductive allocation strategy for grazing stress; there was no significant difference between grazing and enclosure in the contents of BR and IAA in stems (p0.05), but the content of GA3 was significantly lower under overgrazing than that under enclosure (p0.05). The content of BR, IAA and GA3 in leaves decreased with the increase of grazing disturbance (p0.05). The main function of GA3 was to promote stem elongation, which indicated that the decrease of GA3 content under overgrazing might be the main physiological response mechanism of dwarfing formation of Poa pratensis. The content of SOD and MDA in Poa pratensis increased with the increase of grazing disturbance (p0.05). The results showed that MDA accumulation in stems and leaves and membrane lipid oxidation intensified under overgrazing stress, and SOD played an important role in clearing free radicals accumulated under grazing stress. The assembly, functional annotation, classification and metabolic pathway analysis showed that 181,304 Unigenes were obtained after assembly, and the assembly integrity was high; 109,136 Unigenes were obtained by functional annotation, and 15615 differentially expressed genes were identified; the enrichment analysis of GO differentially expressed genes showed that the response stimuli were in the biological process. There were significant differences in enrichment genes; chloroplast enrichment genes were significantly differentially expressed in cell components; oxidoreductase enrichment genes were significantly differentially expressed in molecular functions; KEGG differentially expressed genes were enriched and annotated most frequently in metabolic pathways, and Pathway enrichment analysis was carried out for each pathway. Finally, seven pathways with significant enrichment differences were screened out, including photosynthesis pathway, chloroplast photosynthesis metabolism, oxidative phosphorylation, protease, peroxidase, fatty acid degradation, Notch signaling pathway and so on. To adapt to grazing stress.
【学位授予单位】：甘肃农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S812.8
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