UV-B辐射对紫花苜蓿的胁迫效应及关联光受体作用机制探讨

发布时间：2018-09-17 16:33

【摘要】：紫花苜蓿(Medicago sativa L.),豆科苜蓿属植物,是世上种植最广泛、最重要、资源丰富的多年生牧草之一,有“牧草之王”的美称。本试验以日光灯下培育三周的紫花苜蓿为对照(CK),采用连续7天不同剂量UV-B辐射处理的方法(分别为0.5 h·d-1、1 h·d-1、1.5 h·d-1、2 h·d-1、2.5 h·d-1、3 h·d-1),研究UV-B辐射对紫花苜蓿的形态结构、光合特性、光合色素和紫外吸收物质的影响,结果表明,UV-B辐射不同程度抑制了苜蓿的根长、节间长和株高,1.5 h处理的植株外表呈现枯黄、矮小,茎与根变细弱,叶片发黄、呈现锈斑;每天处理时间大于2 h的植株叶片表面卷曲、叶面积减少、表面皱缩、凹凸不平直至枯死,通过石蜡切片技术观察到这些植株的叶肉细胞塌陷,叶绿体明显减少,茎部细胞边缘呈现歪曲形状,皮层细胞疏松紊乱,细胞因失水呈现塌陷、不饱满的状态;通过扫描电镜观察,每天处理时间大于1.5 h的植株中,叶片表面气孔闭合,表皮细胞凹陷且在处理2.5 h、3 h中凹陷情况严重;随辐射时间的延长,光合速率(Pn)、气孔导度(Cond)和蒸腾速率(Trmmol)呈下降趋势,与CK相比,处理2.5 h中其光合速率下降了87.638%,气孔导度下降了94.536%,处理2 h中其蒸腾速率下降了97.483%,处理1 h中其胞间CO2浓度上升了6.733%,均达到极显著性差异(p0.01),在3 h处理中已难以测出其光合特性各指标;各时间梯度的UV-B辐射对苜蓿中叶绿素a(Chla)、叶绿素b(Chlb)、叶绿素a+b(Chla+b)和类胡萝卜素(Car)含量的影响均有一定的抑制作用,达到极显著性差异(p0.01);UV-B辐射可显著促进紫花苜蓿中紫外吸收物质的含量,与CK相比,总酚和类黄酮的含量在2.5 h的处理中达到最高,分别上升109.951%、18.165%。花青素的含量在2 h处理时最高,上升58.741%,达到极显著性差异(p0.01)。以日光灯下培育三周的紫花苜蓿为对照(CK),设置UV-B、RL-UV-B、RL-DRL-UV-B四种处理,研究Phy参与UV-B辐射胁迫的响应机制,结果表明,与CK相比,短期(2h)UV-B辐射对紫花苜蓿的光合特性、光合色素及营养品质都有一定的抑制作用,在进行10 min红光预辐射后,各项指标都有所回升,加入远红光的预辐射后红光的保护作用消失;短期(2 h)UV-B辐射增加了紫花苜蓿紫外吸收物质的含量;短期(2 h)UV-B辐射使苜蓿体内H2O2含量上升,同时体内过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的活性升高,进行10 min红光预辐射后,降低部分来自UV-B辐射的伤害,加入远红光的预辐射后红光的作用消失,几组处理组均使抗坏血酸过氧化物酶(APX)的活性降低。为了进一步研究UV-B对紫花苜蓿在分子水平上的影响,以及UV-B受体蛋白UVR8和红光受体蛋白Phy之间的相互作用,本实验室克隆了UVR8基因的核心片段,长度为1194 bp。
[Abstract]:Alfalfa (Medicago sativa L.),) is one of the most widely planted, most important and abundant perennial forages in the world, which is called "King of forage". In this experiment, alfalfa cultured under fluorescent lamp for three weeks was used as control (CK), to study the morphological structure and photosynthetic characteristics of alfalfa exposed to UV-B radiation for 7 days with different doses of UV-B radiation (0.5 h d ~ (-1) + 1 h ~ (-1) h ~ (1.5) h ~ (-1) ~ (-1) h ~ (-1) ~ 2 h d ~ (-1) + 2.5 h ~ (-1) 路d ~ (-1) for 3 h 路d ~ (-1). The results showed that the root length, internode length and plant height of alfalfa were inhibited by UV-B radiation in different degree. The plants treated for 1.5 h showed yellow appearance, short appearance, thin stems and roots, yellow leaves and rusty spots. The leaf surface curled up, the leaf area decreased, the surface shrank, and the surface became rugged until the plant died. The mesophyll cells of these plants collapsed and the chloroplast decreased obviously by paraffin section technique. The edge of stem cells presented distorted shape, the cortical cells were loose and disordered, the cells were collapsed because of water loss, and the stomata were closed on the leaf surface of plants treated for more than 1.5 h per day by scanning electron microscope (SEM). The condition of epidermal cell depression was serious during the treatment of 2.5 h / 3 h, and the stomatal conductance (Cond) and transpiration rate (Trmmol) of photosynthetic rate (Pn),) were decreased with the increase of radiation time, compared with CK. The photosynthetic rate and stomatal conductance decreased by 87.638% and 94.536% respectively, transpiration rate decreased 97.483% during 2 h treatment, and the concentration of CO2 increased 6.733% during 1 h treatment, all of which reached significant difference (p0.01), which was difficult in 3 h treatment. The indexes of photosynthetic characteristics were determined. The effects of UV-B radiation on chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll a b (Chla b) and carotenoid (Car) contents in alfalfa were inhibited. The contents of total phenols and flavonoids in alfalfa were higher than those in CK, and the contents of total phenols and flavonoids increased 109.951% and 18.165%, respectively, compared with those of CK. The contents of total phenols and flavonoids reached the highest level in 2.5 h treatment with significant difference (p0.01). The contents of total phenols and flavonoids in alfalfa were increased by 109.951and 18.165g, respectively. The content of anthocyanin was the highest at 2 h, and increased 58.741, reaching a significant difference (p0.01). Four treatments of UV-B,RL-DRL-UV-B were set up in alfalfa cultured under fluorescent lamp for three weeks as control (CK),. The response mechanism of Phy to UV-B radiation stress was studied. The results showed that compared with CK, short-term (2h) UV-B radiation had effect on photosynthesis of alfalfa. Photosynthetic pigment and nutritional quality were inhibited to a certain extent. After 10 min red light pre-irradiation, the indexes increased, and the protective effect of red light disappeared after adding far-red light. Short-term (2 h) UV-B radiation increased the content of ultraviolet absorbents in alfalfa, and short-term (2 h) UV-B radiation increased the content of H2O2 and the activity of peroxidase (POD), superoxide dismutase (POD),) (SOD), catalase (CAT) in alfalfa. After 10 min red light preirradiation, the damage from UV-B radiation was reduced, and the effect of red light was disappeared after adding far red light. The activity of ascorbic acid peroxidase (APX) was decreased in several groups. In order to further study the molecular effect of UV-B on alfalfa and the interaction between UV-B receptor protein UVR8 and red light receptor protein Phy, the core fragment of UVR8 gene was cloned in our laboratory, with the length of 1194 bp..
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S541.9

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