高山植物美丽风毛菊PSII光化学效率和光合色素对短期增补UV-B辐射的响应

在中国科学院海北高寒草甸生态系统实验站的综合观测场, 于植物生长季的不同月份进行短期增补UV-B辐射的模拟试验, 研究了高山植物美丽风毛菊(Saussurea superba)的PSII光化学效率、光合色素和UV-B吸收物质对增强UV-B辐射的响应。结果表明, 尽管差异不显著, 暗适应3 min的PSII最大光化学量子效率在不同月份均有降低的趋势, 说明增强UV-B辐射能加剧光合机构的光抑制。不同月份短期增补UV-B辐射均引起光下PSII实际光化学量子效率和光化学猝灭系数的降低, 以及非光化学猝灭系数的增高, 表明增强UV-B辐射能降低叶片的光能捕获效率, 促进非光化学能量耗散过程。增补UV-B辐射后, 叶片光合色素的含量略有降低趋势, 可能与短时间内光合色素形成过程受抑制和光氧化程度的加剧, 以及叶片厚度的略微降低有关。UV-B吸收物质的含量在不同月份没有一致和较为显著的变化, 说明高原强UV-B环境下生存的美丽风毛菊叶表皮层中由类黄酮和衍生多酚类组成的内部紫外屏蔽物质相对稳定, 倾向于较少受增补UV-B辐射的影响。     

滤除自然光中UV-B辐射成分对高山植物美丽风毛菊光合生理的影响

采用滤除自然光谱中UV-B辐射成分的方法, 探讨了高山植物美丽风毛菊(Saussurea superba)光合机构对青藏高原强UV-B辐射的响应和适应特性。结果表明, 强太阳光中的UV-B成分能引起净光合速率的降低。连续16天不同天气下的观测表明, 滤除UV-B处理时3 min暗适应的光化学量子效率有升高的趋势; 晴天下稳态光化学效率的分析也显示滤除UV-B处理的实际光化学量子效率和光化学猝灭系数有升高趋势, 意味着自然光中的UV-B成分可限制美丽风毛菊叶片PSII反应中心的激发能捕获效率。PSII有效光化学量子效率的增加和非光化学猝灭系数的降低进一步表明, UV-B辐射能导致有效光化学效率的降低和非光化学能量耗散的增加。由上可知, 自然强UV-B辐射是限制美丽风毛菊叶片光合作用的一个因素。滤除UV-B辐射处理对光合色素含量的影响较小, 无论以叶面积还是叶鲜重为基础的滤除UV-B处理仅有微弱的增加趋势, 说明强UV-B辐射具有加速光合色素的光氧化进程, 促进细胞成熟和叶片衰亡的潜在作用。同样UV-B吸收物质的含量也几乎没有变化, 表明强太阳辐射环境下生活的高山植物美丽风毛菊叶表皮层中已具有较多的紫外线屏蔽物质, 足以抵御目前环境中强太阳UV-B辐射可能引起的伤害, 较少受UV-B辐射波动的影响。     

不同剂量~(137)Cs-γ辐射对毛竹幼苗叶片叶绿素荧光参数的影响

利用不同剂量的137Cs-γ射线对毛竹(Phyllostachys heterocycla ‘Pubescens’)种子进行辐射,测定实生苗叶片中的光合色素含量和叶绿素荧光参数等指标,探讨辐射对毛竹幼苗生长的影响,为筛选有利的突变单株奠定良好基础。结果表明:30或60Gy的137Cs-γ射线辐射后,毛竹幼苗的光合色素含量以及最大荧光强度(Fm)、可变荧光强度(Fv)、PSII最大光化学效率(Fv/Fm)、PSII的潜在活性(Fv/Fo)、PSII实际光化学效率(Yield)和表观光合电子传递速率(ETR)等荧光参数值均高于90Gy辐射处理,说明较低剂量辐射后PSII反应中心的能量捕获效率高,且具有较强的光合能力;而90Gy的137Cs-γ射线辐射对毛竹的影响则与之相反。不同处理剂量之间叶片光能耗散程度以及表观光合电子传递速率-光合有效辐射(ETR-PAR)响应曲线的分析结果也进一步证实了以上结论。     

氯化胆碱对低温弱光下黄瓜幼苗叶片细胞膜和光合机构的保护作用

1.07mmol／L氯化胆碱处理降低了低温弱光（6℃．PFD100μmol m^-2s^-1）下黄瓜幼苗叶片膜脂组分中主要是磷脂酰甘油（PG）的饱和脂肪酸含量,增加了膜脂不饱和度：减缓了膜透性的下降、MDA的产生速率、叶绿素的降解及PSII最大量子效率（Fv/Fm）、捕光效率（Fv＇／Fm＇）、光化学猝灭系数（qp）、实际光化学效率（ФPSII）和抗氧化酶POD、APX及CAT活性的下降;提高了非光化学猝灭系数（NPQ）和脯氨酸的含量。以上结果表明氯化胆碱处理保护了低温弱光对黄瓜叶片细胞膜和光合机构的伤害。     

模拟酸雨对白簕叶片抗氧化酶活性及叶绿素荧光参数的影响

采用棚内盆栽方法,设置pH值5.6(对照)、4.0、3.0和2.0的模拟酸雨胁迫试验,探讨其对白簕幼苗叶片MDA含量、保护酶活性、叶绿素含量、气体交换参数和叶绿素荧光参数的影响。结果表明,随着模拟酸雨pH值的降低,MDA含量呈先降低后升高的趋势;SOD活性逐渐降低,POD活性逐渐升高,APX活性呈先升高后降低的变化。叶绿素a、叶绿素b、总叶绿素含量均比对照高,在pH 4.0时达最大值。气孔限制值(Ls)、PSII实际光化学量子产量(ΦPSII)、光化学淬灭系数(qP)均随pH值的降低而下降,净光速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、水分利用效率(WUE)、PSII最大光化学效率(Fv/Fm)、PSII的潜在活性(Fv/Fo)、非光化学淬灭系数(qN)呈先升高后降低趋势,且也都在pH 4.0时达最大值。由此推测,pH 4.0的酸雨处理有利于白簕幼苗的生长,表明白簕幼苗可能喜欢生活在微酸环境中,但是随着酸度加强,反而起到抑制作用。     

不同剂量^137Cs-γ辐射对毛竹幼苗叶片叶绿素荧光参数的影响

利用不同剂量的137Cs-γ射线对毛竹（Phyllostachys heterocycla ‘Pubescens’）种子进行辐射, 测定实生苗叶片中的光合色素含量和叶绿素荧光参数等指标, 探讨辐射对毛竹幼苗生长的影响, 为筛选有利的突变单株奠定良好基础。结果表明：30或60 Gy的137Cs-γ射线辐射后, 毛竹幼苗的光合色素含量以及最大荧光强度（Fm）、可变荧光强度（Fv）、PSII最大光化学效率（Fv/Fm）、PSII的潜在活性（Fv/Fo）、PSII实际光化学效率（Yield）和表观光合电子传递速率（ETR）等荧光参数值均高于90 Gy辐射处理, 说明较低剂量辐射后PSII反应中心的能量捕获效率高, 且具有较强的光合能力; 而90 Gy的137Cs-γ射线辐射对毛竹的影响则与之相反。不同处理剂量之间叶片光能耗散程度以及表观光合电子传递速率-光合有效辐射（ETR-PAR）响应曲线的分析结果也进一步证实了以上结论。     

供镁水平对油桐幼苗生长及光合特性的影响

采用营养液砂培试验,研究不同供镁水平对油桐幼苗生长、光合特性及叶绿素荧光参数等的影响。结果表明,低镁浓度(Mg2+2 mmol·L-1)显著抑制了油桐的生长,叶绿素含量、Ru BP羧化酶及PEPC活性、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(Ls)、水分利用效率(WUE)、最大光化学效率(Fv/Fm)、实际光化学量子效率(ΦPSII)、PSII的潜在活性(Fv/Fo)及光化学淬灭系数(q P)显著下降(P0.05),胞间CO2浓度(Ci)、初始荧光(Fo)、非光化学淬灭系数(NPQ)有所升高;高镁浓度(Mg2+4 mmol·L-1)也抑制了油桐幼苗的生长,导致叶片叶绿素含量、Ru BP羧化酶活性、Pn、Gs、Fv/Fm、Fv/Fo及q P均下降(P0.05);随着供镁水平的增加,油桐的生长量、叶绿素含量、Ru BP羧化酶及PEPC活性、Pn呈先增加后降低的趋势;当镁离子浓度为2~4 mmol·L-1时,有利于油桐幼苗正常生长,缺镁胁迫下油桐光合速率的下降主要是由光合机构活性降低的非气孔因素引起的。     

紫外辐射对菹草成株生理特性的影响

研究不同剂量UV-B辐射下菹草生理特征变化,在光合有效辐射、UV-A辐射一致的条件下,对菹草进行不同剂量UV-B辐射,测定菹草叶片光合色素含量及生理生化指标。结果表明:≤10.8 k J/m2剂量辐射可促进叶绿素及类胡萝卜素含量增加,衰亡阶段起抑制作用,10.8 k J/m2一直起到抑制作用,且随剂量的增加,抑制作用增强;UV-B辐射初期可促进过氧化氢酶(CAT)、过氧化物(POD)酶活性及丙二醛(MDA)含量升高,且随辐射剂量增加而逐渐升高,但随辐射时间延长,CAT、POD酶活性、MDA含量均有所降低,超氧化物歧化酶活性随辐射时间延长逐渐升高,且随辐射剂量增加而增加;短期辐射可促进叶片可溶性蛋白质和可溶性糖的合成,其含量随辐射剂量增加而升高,长期辐射起抑制作用,且随辐射剂量增加,抑制作用增强。因此,春末夏初野外强UV-B辐射可能是促进菹草大批衰亡的重要原因。     

模拟酸雨对白筋叶片抗氧化酶活性及叶绿素荧光参数的影响

采用棚内盆栽方法, 设置pH值5.6 （对照）、4.0、3.0和2.0的模拟酸雨胁迫试验, 探讨其对白簕幼苗叶片MDA含量、保护酶活性、叶绿素含量、气体交换参数和叶绿素荧光参数的影响。结果表明, 随着模拟酸雨pH值的降低, MDA含量呈先降低后升高的趋势; SOD活性逐渐降低, POD活性逐渐升高, APX活性呈先升高后降低的变化。叶绿素a、叶绿素b、总叶绿素含量均比对照高, 在pH 4.0时达最大值。气孔限制值（Ls）、PSII实际光化学量子产量（ΦPSII）、光化学淬灭系数（qP）均随pH值的降低而下降, 净光速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）、水分利用效率（WUE）、PSII最大光化学效率（Fv/Fm）、PSII的潜在活性（Fv/Fo）、非光化学淬灭系数（qN）呈先升高后降低趋势, 且也都在pH 4.0时达最大值。由此推测, pH 4.0的酸雨处理有利于白簕幼苗的生长, 表明白簕幼苗可能喜欢生活在微酸环境中, 但是随着酸度加强, 反而起到抑制作用。     

UV-B对设施桃叶片光合功能及叶绿体超微结构的影响

对温室栽培的油桃中油5号(Prunus persica var. nectarina cv.‘Zhongyou5’)适量补充UV-B,分析其对桃叶片光合功能及叶绿体超微结构的影响。结果表明,UV-B处理下各色素含量均有不同程度的增加,其中叶绿素b的含量和净光合速率(P_n)提升幅度较大。相较于未补充UV-B的桃树(对照), UV-B处理的F_v/F_m无显著变化, F_v’/F_m’比值、光化学猝灭系数(qP)、非光化学猝灭系数(qN)以及PSII实际光化学量子效率(Φ_PSII)均有显著或极显著升高。透射电镜结果显示,UV-B处理下叶绿体基质片层空隙小,堆叠紧密,叶绿体外膜边缘清晰。可见,温室内适量补充UV-B可快速改善叶片叶绿体的超微结构,提升叶绿素分子捕获光能及向PSII传递的能力,增大PSII反应中心的开放程度,提高实际光能转化效率和PSII电子传递量子效率,提高叶片的光合功能。该研究为设施果树光合性能改善和UV-B合理利用提供了理论依据。     

The Regulation of Exogenous Jasmonic Acid on UV-B Stress Tolerance in Wheat

Enhanced ultraviolet-B radiation (UV-B, 280?C320?nm) is recognized as one of the environmental stress factors that cannot be neglected. Jasmonic acid (JA) is an important signaling molecule in a plant??s defense against biotic and abiotic stresses. To determine the role of exogenous JA in the resistance of wheat to stress from UV-B radiation, wheat seedlings were exposed to 0.9?kJ?m^?2?h^?1 UV-B radiation for 12?h after pretreatment with 1 and 2.5?mM JA, and the activity of antioxidant enzymes, the level of malondialdehyde (MDA), the content of UV-B absorbing compounds, photosynthetic pigments, and proline and chlorophyll fluorescence parameters were measured. The results of two-way ANOVA illustrated that the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), MDA level, anthocyanin and carotenoid (Car) content, and almost all chlorophyll fluorescence parameters were significantly affected by UV-B, JA, and UV-B?×?JA (P?<?0.05) [the maximal efficiency of photosystem II photochemistry (F _v/F _m) was not affected significantly by UV-B radiation]. Duncan??s multiple-range tests demonstrated that UV-B stress induced a significant reduction in plant photosystem II (PSII) function and SOD activity and an increased level of membrane lipid peroxidation, indicative of the deleterious effect of UV-B radiation on wheat. JA pretreatment obviously mitigated the detrimental effect of UV-B on PSII function by increasing F _v/F _m, reaction centers?? excitation energy capture efficiency (F _v??/F _m??), effective photosystem II quantum yield (??PSII), and photosynthetic electron transport rate (ETR), and by decreasing nonphotochemical quenching (NPQ) of wheat seedlings. Moreover, the activity of SOD and the content of proline and anthocyanin were provoked by exogenous JA. However, the MDA level was increased and Car content was decreased by exogenous JA with or without the presence of supplementary UV-B, whereas the contents of chlorophyll and flavonoids and related phenolics were not affected by exogenous JA. Meanwhile, exogenous JA resulted in a decrease of CAT and POD activities under UV-B radiation stress. These results partly confirm the hypothesis that exogenous JA could counteract the negative effects of UV-B stress on wheat seedlings to some extent.     

UV-B 胁迫下NaHSO3 对红芸豆叶片的保护作用

为了减轻UV-B辐射对植物叶片的伤害, 本研究以离体红芸豆叶片为实验材料, 通过外源施加NaHSO3的方法探讨了UV-B辐射下NaHSO3 对离体红芸豆叶片的保护作用。结果表明：与未处理对照相比较, 用0.5 mmol.L-1 NaHSO3处理的离体红芸豆叶片表面褐色斑减少、边缘蜷曲及萎蔫程度降低;且能延缓叶片中叶绿素和类胡萝卜素含量的降低;使类黄酮含量升高; 叶片中过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性升高, 过氧化氢(H2O2)含量降低。进一步研究发现NaHSO3处理能明显延缓PSⅡ原初光能转换效率的降低;增强PSⅡ的电子传递能力, 减少叶绿体内有害自由基的产生, 减缓叶绿体内光合机构遭受破坏的程度。以上结果表明NaHSO3可能通过提高POD和APX的活性、降低自由基产生及保护光合色素等来实现UV-B胁迫下对红芸豆叶片的保护作用。     

Temperature-dependent adjustment of the thermal stability of photosystem II in vivo: possible involvement of xanthophyll-cycle pigments

Moderately elevated temperatures induce a rapid increase in the heat and light resistance of photosystem II (PSII) in higher-plant leaves. This phenomenon was studied in intact potato leaves exposed to 35 °C for 2 h, using chlorophyll fluorometry, kinetic and difference spectrophotometry and photoacoustics. The 35 °C treatment was observed to cause energetic uncoupling between carotenoids and chlorophylls: (i) the steady-state chlorophyll fluorescence emission excited by a blue light beam (490 nm) was noticeably reduced as compared to fluorescence elicited by orange light (590 nm) and (ii) the quantum yield for photosynthetic oxygen evolution in blue light (400–500 nm) was preferentially reduced relative to the quantum yield measured in red light (590–710 nm). Analysis of the chlorophyll-fluorescence and light-absorption characteristics of the heated leaves showed numerous analogies with the fluorescence and absorption changes associated with the light-induced xanthophyll cycle activity, indicating that the carotenoid species involved in the heat-induced pigment uncoupling could be the xanthophyll violaxanthin. More precisely, the 35 °C treatment was observed to accelerate and amplify the non-photochemical quenching of chlorophyll fluorescence (in both moderate red light and strong white light) and to cause an increase in leaf absorbance in the blue-green spectral region near 520 nm, as do strong light treatments which induce the massive conversion of violaxanthin to zeaxanthin. Interestingly, short exposure of potato leaves to strong light also provoked a significant increase in the stability of PSII to heat stress. It was also observed that photosynthetic electron transport was considerably more inhibited by chilling temperatures in 35 °C-treated leaves than in untreated leaves. Further, pre-exposure of potato leaves to 35 °C markedly increased the amplitude and the rate of light-induced changes in leaf absorbance at 505 nm (indicative of xanthophyll cycle activity), suggesting the possibility that moderately elevated temperature increased the accessibility of violaxanthin to the membrane-located de-epoxidase. This was supported by the quantitative analysis of the xanthophyll-cycle pigments before and after the 35 °C treatment, showing light-independent accumulation of zeaxanthin during mild heat stress. Based on these results, we propose that the rapid adjustment of the heat resistance of PSII may involve a modification of the interaction between violaxanthin and the light-harvesting complexes of PSII. As a consequence, the thermoresistance of PSII could be enhanced either directly through a conformational change of PSII or indirectly via a carotenoid-dependent modulation of membrane lipid fluidity.Abbreviations and Symbols Fo and Fm initial and maximal level of chlorophyll fluorescence, respectively - Fv = Fm — Fo variable chlorophyll fluorescence - LHC(II) light-harvesting chlorophylla/b-protein complexes (of PSII) - photoacoustically measured quantum yield of photosynthetic oxygen evolution (in relative values) - _P fluorimetrically measured quantum yield of PSII photochemistry in the light - PFD photon flux density - q_E pH dependent quenching of chlorophyll fluorescence We thank Dr. J-L Montillet (CEA-Cadarache) for the use of his HPLC apparatus and Professor Y. Lemoine (University of Lille, France) for technical advice on HPLC.     

Responses of the flavonoid pathway to UV-B radiation stress and the correlation with the lipid antioxidant characteristics in the desert plant Caryopteris mongolica

Caryopteris mongolica is a dwarf shrub mainly found in grassland and desert areas of north-west China, and which can survive severe environmental stress. This study aimed to assess the responses of the flavonoid pathway to UV-B radiation treatments and its correlation to the lipid peroxide and antioxidant systems in C. mongolica. In UV-B radiation experiments, plants were exposed to UV-B radiation treatments with a intensity of 30 J/s for 1, 4 and 24 h, respectively. A control group without UV-B radiation treatment was also used. The chlorophyll fluorescence parameters, contents of chlorophyll and carotenoid, levels of lipid peroxidation, activities of antioxidant system enzymes, accumulations of total flavonoids and anthocyanins, and activities of phenylalanine ammonialyase (PAL) and chalcone isomerase (CHI) under different UV-B radiation treatments were investigated. The correlations between products and key enzymes in the flavonoid pathway and the lipid peroxide and antioxidant systems were also analyzed. The results showed that chlorophyll fluorescence parameters decreased within 24 h of treatment. The chlorophyll contents decreased within 4 h and remained stable after 24 h. Carotenoid content significantly increased. The level of MDA, the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD) and the contents of total flavonoids and anthocyanidins increased, while catalase (CAT) activity decreased under UV-B stress. The activities of PAL and CHI also increased with the increased content of total flavonoids. The flavonoid products anthocyanidins had a significant positive correlation with MDA level, as well as the activities of antioxidant enzyme SOD. In conclusion, UV-B radiation induced the degradation of photosynthetic pigments and decreased photochemical efficiency of Photosystem II; increased the contents of MDA, total flavonoids and anthocyanidins; and also enhanced activities of antioxidant enzymes (SOD, APX and POD) and key enzymes (PAL and CHI) in the flavonoid pathway in C. mongolica. Thus, we speculate that the flavonoid pathway were involved in the regulation of stress resistance in C. mongolica.     

追施氮肥时期对冬小麦旗叶叶绿素荧光特性的影响

在大田条件下,研究了不同追氮时期对小麦旗叶叶绿素荧光特性、光合速率及籽粒产量的影响.结果表明,拔节期追肥较起身期或挑旗期追肥,改善了小麦旗叶PSⅡ的活性(F_v/F_o)、光化学最大效率(F_v/F_m)、光化学猝灭系数(qP)、实际量子产量(ΦPSⅡ)及光合速率,降低了籽粒灌浆中前期非辐射能量耗散,有利于叶片所吸收的光能较充分地用于光合作用,提高了籽粒灌浆后期非辐射能量的耗散,减缓了叶片光抑制程度和衰老进程.拔节期追肥可显著增加穗粒数和千粒重,提高产量.     

增强UV-B辐射和氮对谷子叶光合色素及非酶促保护物质的影响

以谷子(Setaria italica(L)Beauv.)为对象,从拔节期开始持续给予低氮(1.875 mmol/L)和高氮(15 mmol/L)两种氮供应条件并从抽穗期开始进行26 d两种强度(4.29、7.12 kJ·m-2·d-1)的增强UV-B辐射处理,研究了谷子叶中光合色素含量、类黄酮含量和苯丙氨酸解氨酶(PAL)活性的变化.结果表明:与高氮供应条件相比,低氮供应条件明显降低了谷子叶中光合色素含量但提高了类胡萝卜素/叶绿素含量比值;在开花期中段和灌浆期中段,高氮供应条件下谷子叶中光合色素含量对增强UV-B辐射比低氮供应条件下的谷子更敏感.从灌浆期开始到处理结束,两种影响因子对谷子叶中类黄酮含量均有显著影响,增强UV-B辐射导致谷子叶中类黄酮含量逐渐升高,且相同增强UV-B辐射强度下低氮供应条件下的谷子叶中类黄酮含量明显高于高氮供应条件下的谷子.谷子叶中PAL活性对两种影响因子的响应较类黄酮含量更加敏感,低氮供应条件使谷子叶中PAL活性明显提高.结合上述指标的相关性分析结果可知,低氮供应条件加强了处于繁殖期主要阶段的谷子叶中类黄酮的积累,并使谷子叶中的类胡萝卜素/叶绿素含量比值明显提高,进而有助于维持谷子叶中光合色素含量在增强UV-B辐射条件下的相对稳定性,对植株抵抗UV-B辐射伤害有利.     

UV-B辐射对烟草光合色素和几种酶的影响

对UV-B胁迫条件下烟草叶片相关生理生化指标的变化进行研究.结果表明,UV-B辐照后,烟草叶片内光合色素(叶绿素a、叶绿素b、类胡萝卜素)的含量均呈上升趋势,3种色素比对照分别上升了21%、10%、27%;可溶性蛋白含量呈先上升后下降趋势;过氧化物酶活性明显上升,同工酶图谱分析证实,有一种新的过氧化物酶同工酶表达;利用重组噬夏孢欧文氏菌(Erwinia uredovora)GGPP合成酶免疫家兔,制备了兔抗GGPP合成酶的抗血清.Western blot检测显示,UV-B辐照可使烟草叶片GGPP合成酶(GGPS)的表达量显著提高.