【摘要】：紫花苜蓿(Medicago sativa L.),豆科苜蓿屬植物,是世上種植最廣泛、最重要、資源豐富的多年生牧草之一,有“牧草之王”的美稱。本試驗以日光燈下培育三周的紫花苜蓿為對照(CK),采用連續(xù)7天不同劑量UV-B輻射處理的方法(分別為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輻射對紫花苜蓿的形態(tài)結(jié)構(gòu)、光合特性、光合色素和紫外吸收物質(zhì)的影響,結(jié)果表明,UV-B輻射不同程度抑制了苜蓿的根長、節(jié)間長和株高,1.5 h處理的植株外表呈現(xiàn)枯黃、矮小,莖與根變細弱,葉片發(fā)黃、呈現(xiàn)銹斑;每天處理時間大于2 h的植株葉片表面卷曲、葉面積減少、表面皺縮、凹凸不平直至枯死,通過石蠟切片技術(shù)觀察到這些植株的葉肉細胞塌陷,葉綠體明顯減少,莖部細胞邊緣呈現(xiàn)歪曲形狀,皮層細胞疏松紊亂,細胞因失水呈現(xiàn)塌陷、不飽滿的狀態(tài);通過掃描電鏡觀察,每天處理時間大于1.5 h的植株中,葉片表面氣孔閉合,表皮細胞凹陷且在處理2.5 h、3 h中凹陷情況嚴重;隨輻射時間的延長,光合速率(Pn)、氣孔導度(Cond)和蒸騰速率(Trmmol)呈下降趨勢,與CK相比,處理2.5 h中其光合速率下降了87.638%,氣孔導度下降了94.536%,處理2 h中其蒸騰速率下降了97.483%,處理1 h中其胞間CO2濃度上升了6.733%,均達到極顯著性差異(p0.01),在3 h處理中已難以測出其光合特性各指標;各時間梯度的UV-B輻射對苜蓿中葉綠素a(Chla)、葉綠素b(Chlb)、葉綠素a+b(Chla+b)和類胡蘿卜素(Car)含量的影響均有一定的抑制作用,達到極顯著性差異(p0.01);UV-B輻射可顯著促進紫花苜蓿中紫外吸收物質(zhì)的含量,與CK相比,總酚和類黃酮的含量在2.5 h的處理中達到最高,分別上升109.951%、18.165%�；ㄇ嗨氐暮吭�2 h處理時最高,上升58.741%,達到極顯著性差異(p0.01)。以日光燈下培育三周的紫花苜蓿為對照(CK),設置UV-B、RL-UV-B、RL-DRL-UV-B四種處理,研究Phy參與UV-B輻射脅迫的響應機制,結(jié)果表明,與CK相比,短期(2h)UV-B輻射對紫花苜蓿的光合特性、光合色素及營養(yǎng)品質(zhì)都有一定的抑制作用,在進行10 min紅光預輻射后,各項指標都有所回升,加入遠紅光的預輻射后紅光的保護作用消失;短期(2 h)UV-B輻射增加了紫花苜蓿紫外吸收物質(zhì)的含量;短期(2 h)UV-B輻射使苜蓿體內(nèi)H2O2含量上升,同時體內(nèi)過氧化物酶(POD)、超氧化物歧化酶(SOD)、過氧化氫酶(CAT)的活性升高,進行10 min紅光預輻射后,降低部分來自UV-B輻射的傷害,加入遠紅光的預輻射后紅光的作用消失,幾組處理組均使抗壞血酸過氧化物酶(APX)的活性降低。為了進一步研究UV-B對紫花苜蓿在分子水平上的影響,以及UV-B受體蛋白UVR8和紅光受體蛋白Phy之間的相互作用,本實驗室克隆了UVR8基因的核心片段,長度為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..
【學位授予單位】：河南師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S541.9

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