過(guò)度放牧下高原早熟禾矮小化及其形成機(jī)理
發(fā)布時(shí)間：2018-08-27 09:24
【摘要】：高寒草甸是青藏高原的主體,對(duì)維持生態(tài)系統(tǒng)功能有重要的作用,長(zhǎng)期過(guò)度放牧下,高寒草甸主要優(yōu)勢(shì)植物高原早熟禾(Poa alpigena)表現(xiàn)出明顯的矮小化現(xiàn)象。研究高寒草甸植物矮小化形成機(jī)理,為深刻解析高寒草甸退化機(jī)理有重要的科學(xué)意義。因此,本文以高原早熟禾為研究對(duì)象,通過(guò)野外放牧試驗(yàn)和室內(nèi)試驗(yàn)相結(jié)合的方法,系統(tǒng)研究了放牧對(duì)高原早熟禾個(gè)體性狀、形態(tài)解剖結(jié)構(gòu)、組織器官激素、基因表達(dá)的影響,從個(gè)體、細(xì)胞、分子水平深入研究過(guò)度放牧對(duì)高原早熟禾矮小化形成機(jī)理,主要結(jié)論如下:1在長(zhǎng)期放牧干擾下,除葉片數(shù)外高原早熟禾株高、分枝數(shù)、葉片數(shù)、葉長(zhǎng)、葉寬、葉面積、莖粗、莖長(zhǎng)、根長(zhǎng)、根粗、穗長(zhǎng)、總?cè)~質(zhì)量、單葉質(zhì)量、莖重、穗重、根重、全株重等性狀均出現(xiàn)顯著變小的特征(p0.05);通過(guò)構(gòu)建高原早熟禾性狀可塑性變化譜,發(fā)現(xiàn)株高、莖長(zhǎng)、分蘗數(shù)、全株重等可塑性幅度較大,為放牧響應(yīng)的敏感指標(biāo),說(shuō)明過(guò)度放牧下高原早熟禾株高、莖長(zhǎng)、個(gè)體生物量等性狀指標(biāo)的減小導(dǎo)致了高原早熟禾矮小化的發(fā)生;通過(guò)高原早熟禾個(gè)體生物量與性狀指標(biāo)間相關(guān)性分析,株高、葉長(zhǎng)、葉寬、葉面積、莖長(zhǎng)、穗長(zhǎng)、分枝數(shù)等性狀與個(gè)體生物量呈現(xiàn)顯著正相關(guān)關(guān)系(p0.01),說(shuō)明這些指標(biāo)的減小是導(dǎo)致高原早熟禾長(zhǎng)期放牧下個(gè)體生物量降低的主要因子。2通過(guò)對(duì)放牧和圍封下高原早熟禾莖葉解剖結(jié)構(gòu)的研究,結(jié)果表明:葉片厚度、表皮角質(zhì)層、上下表皮細(xì)胞面積、韌皮部厚度,隨著放牧干擾強(qiáng)度的增加而增大(p0.05);葉肉細(xì)胞面積、莖表皮細(xì)胞面積、木質(zhì)部厚度、導(dǎo)管壁厚度隨著放牧干擾強(qiáng)度的增加而減小(p0.05),而葉肉細(xì)胞密度無(wú)顯著差異;葉上下表皮細(xì)胞面積、上表皮角質(zhì)層厚度、葉木質(zhì)部厚度可塑性指數(shù)較高,PI均大于0.5。莖導(dǎo)管直徑、表皮細(xì)胞大小、表皮角質(zhì)層厚度可塑性指數(shù)較高,PI大于0.4;說(shuō)明在過(guò)度放牧下葉片厚度、表皮角質(zhì)層厚度、韌皮部厚度的增加,是高原早熟禾為了抵御牲畜啃食而采取的防御策略。而過(guò)度放牧下葉肉細(xì)胞面積、莖表皮細(xì)胞面積的減小,而密度無(wú)顯著變化,說(shuō)明高原早熟禾葉片和莖桿趨于縮短,進(jìn)而導(dǎo)致了矮小化的發(fā)生。3通過(guò)對(duì)放牧與圍封下高原早熟禾葉肉細(xì)胞超微結(jié)構(gòu)特征的研究,結(jié)果表明,隨著放牧干擾強(qiáng)度的增加,葉肉細(xì)胞面積、細(xì)胞壁厚、嗜餓顆粒數(shù)、葉綠體面積、線粒體數(shù)量及線粒體大小逐漸減小(p0.05)。高原早熟禾通過(guò)改變?nèi)~肉細(xì)胞葉綠體和線粒體的結(jié)構(gòu)和大小來(lái)響應(yīng)放牧脅迫,由此推斷葉綠體和線粒體結(jié)構(gòu)和大小的改變可能是高原早熟禾矮小化形成的細(xì)胞學(xué)機(jī)制。4通過(guò)對(duì)放牧和圍封下高原早熟禾內(nèi)源激素油菜素內(nèi)酯(GA3)、生長(zhǎng)素(IAA)、赤霉素(BR),以及丙二醛(MDA)和超氧化物歧化酶(SOD)的分析發(fā)現(xiàn),過(guò)度放牧下高原早熟禾根部BR、IAA、GA3含量顯著高于圍封條件下(p0.05),說(shuō)明過(guò)度放牧下,三種激素主要提供地下部分的生長(zhǎng),這是對(duì)放牧脅迫所采取的繁殖分配策略;莖中BR、IAA含量放牧與圍封無(wú)顯著差異(p0.05),而GA3含量過(guò)度放牧顯著小于圍封(p0.05),葉中BR、IAA、GA3含量隨著放牧干擾的增加而減小(p0.05),GA3的主要功能是促進(jìn)莖的伸長(zhǎng),由此說(shuō)明過(guò)度放牧下GA3含量的減小可能是高原早熟禾矮小化形成的主要生理響應(yīng)機(jī)制;高原早熟禾SOD和MDA含量隨著放牧干擾的增加而增加(p0.05),說(shuō)明在過(guò)度放牧脅迫下莖葉中MDA含量積累,膜脂氧化程度加劇,在清除放牧脅迫所積累的自由基過(guò)程中SOD起重要作用。5采用HiSeqTM 2500高通量測(cè)序技術(shù)對(duì)高原早熟禾矮小化植株和正常植株基因表達(dá)進(jìn)行了轉(zhuǎn)錄組測(cè)序,并對(duì)測(cè)得序列進(jìn)行了組裝、功能注釋、分類和代謝通路分析。結(jié)果表明,組裝后共獲得181,304條Unigene,組裝完整性較高;對(duì)Unigene進(jìn)行功能注釋,共獲得109,136條Unigene的注釋結(jié)果,識(shí)別差異表達(dá)基因15615條;GO差異表達(dá)基因富集分析表明,生物學(xué)進(jìn)程中,響應(yīng)刺激類富集基因差異顯著;細(xì)胞組分中,葉綠體富集基因差異表達(dá)顯著;分子功能中,氧化還原酶活性類富集基因差異表達(dá)顯著;KEGG差異表達(dá)基因富集注釋結(jié)果顯示,代謝通路上差異表達(dá)基因富集注釋最多,進(jìn)一步對(duì)各通路進(jìn)行Pathway富集分析和篩選,最后篩選出富集差異顯著的通路有光合作用途徑、葉綠體光合代謝、氧化磷酸化、蛋白酶、過(guò)氧化物酶、脂肪酸降解、Notch信號(hào)途徑等7富集差異通路。說(shuō)明在放牧脅迫下高原早熟禾經(jīng)歷了復(fù)雜的生理過(guò)程,通過(guò)這類功能基因的調(diào)整來(lái)適應(yīng)放牧脅迫。
[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.
【學(xué)位授予單位】：甘肅農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：S812.8
本文編號(hào)：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.
【學(xué)位授予單位】：甘肅農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：S812.8
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