CaCl_2对UV-B辐射下菠菜叶片光合特性的影响

以"丹麦旺盛菠菜"为材料,通过UV-B和CaCl2复合处理,测定光合色素含量、Hill反应活力、叶绿素荧光、MDA含量和抗氧化酶活性等参数,探讨了CaCl2对UV-B辐射下菠菜叶片电子传递链和光合膜酶保护系统的影响。结果表明,UV-B处理下,光合色素含量、chl/car、类囊体膜上PSII潜在活性(Fv/Fo)、光化学淬灭系数(qP)、非光化学淬灭系数(qN)、PSII光量子产量(ΦPSⅡ)、原初光能转化效率(Fv/Fm),以及Hill反应活力等降低,chla/chlb和MDA含量升高;喷洒CaCl2可不同程度缓解UV-B的伤害。不同处理下,POD、SOD和CAT活性的变化呈现补偿效应。UV-B强度与菠菜叶片PSII功能受损程度呈正相关,CaCl2则主要通过提高chlb含量、类囊体膜上的光量子产量和POD活性,以缓解伤害。重度UV-B辐射下,CaCl2使chlb含量显著提高可能是导致PSII捕光效率提高的重要因素。     

Nitric oxide plays a role as second messenger in the ultraviolet-B irradiated green alga <Emphasis Type="Italic">Chlorella pyrenoidosa</Emphasis>

Nitric oxide (NO) stimulated the activity of plasma membrane H⁺-ATPase, 5′-nucleotidase, peroxidase, ascorbate peroxidase and glutathione reductase in ultraviolet B (UV-B) irradiated Chlorella pyrenoidosa. It also boosted the activity of nitrogen-metabolism enzymes such as nitrate reductase, nitrite reductase, glutamine synthetase, which were inhibited by UV-B irradiation. The chlorophyll fluorescence ratio (Fv/Fm) of the UV-B irradiated algae and decreased continuously after the cells were transferred to UV-B irradiation. A continuing decrease of the Fv/Fm was observed even after the cells were transferred to photosynthetically active radiation (PAR). After adaptation for 8 h under PAR (after treatment with nitric oxide), Fv/Fm recovered to 55 % of normal levels — without NO the value approached zero. Exogenous NO stopped the decay of chlorophyll and thylakoid membrane in cells exposed to UV-B irradiation. NO plays probably a key role in damage induced by UV-B irradiation in green algae.     

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。     

The effects of salt stress on photosynthetic electron transport and thylakoid membrane proteins in the cyanobacterium Spirulina platensis

The response of Spirulina (Arthrospira) platensis to high salt stress was investigated by incubating the cells in light of moderate intensity in the presence of 0.8 M NaCl. NaCl caused a decrease in photosystem II (PSII) mediated oxygen evolution activity and increase in photosystem I (PSI) activity and the amount of P700. Similarly maximal efficiency of PSII (Fv/Fm) and variable fluorescence (Fv/Fo) were also declined in salt-stressed cells. Western blot analysis reveal that the inhibition in PSII activity is due to a 40 % loss of a thylakoid membrane protein, known as D1, which is located in PSII reaction center. NaCl treatment of cells also resulted in the alterations of other thylakoid membrane proteins: most prominently, a dramatic diminishment of the 47-kDa chlorophyll protein (CP) and 94-kDa protein, and accumulation of a 17-kDa protein band were observed in SDS-PAGE. The changes in 47-kDa and 94-kDa proteins lead to the decreased energy transfer from light harvesting antenna to PSII, which was accompanied by alterations in the chlorophyll fluorescence emission spectra of whole cells and isolated thylakoids. Therefore we conclude that salt stress has various effects on photosynthetic electron transport activities due to the marked alterations in the composition of thylakoid membrane proteins.     

UV-B辐射对蚕豆叶膜脂过氧化的影响及其机制

温室种植的吞豆在0（CK）,8．82kJ/m2(T1)和12．6kJ/m2(T2)3种剂量的紫外线B（UV－B）辐射引起膜脂变化及其机制的研究结果表明,UV0B处理后,蚕豆叶片中丙二醛（MDA）和H2O2含量升高,膜脂肪酸不饱和度指数（IUFA）降低,脂氧合酶（LOX）活性升高,超氧歧化酶（SOD）活性稍有波动,而3种多胺－腐胺（Put)精胺（Spd)和尸胺（Spn)在照射7天后均有积累,但在处理后期（21d)有所回落,推测由LOX主导的酶促膜过氧化作用和氧自由基引起的非酶促过作用在膜结构的破坏中起重要作用,SOD活性和多胺含量的变化蚕豆对UV－B胁迫的一种适应性生理反应。     

模拟酸雨胁迫下硅对髯毛箬竹光合特性的影响

以髯毛箬竹为试验材料,研究了模拟酸雨胁迫(pH 3.0)下硅对髯毛箬竹叶片叶绿素相对含量、光合作用日变化以及叶绿素荧光特性等的影响.结果表明:20和100 mg·L^-1 Na₂SiO₃预处理可以不同程度地抑制酸雨胁迫下髯毛箬竹叶片叶绿素含量的显著下降,且以100 mg·L^-1浓度处理效果最佳,叶绿素含量可提高22.7%,而高浓度(500 mg·L^-1)预处理则无缓解作用-酸雨胁迫下,髯毛箬竹光合“午休”现象加重,日平均净光合速率(P_n)、气孔导度(G_s)和气孔限制值(L_s)明显降低,而胞间CO₂浓度(C_i)增大,经过20～100 mg·L^-1硅预处理后,P_n、G_s、L_s不同程度增加,而C_i有所降低,且以100 mg·L^-1硅预处理效果最佳,日平均P_n增加39.2%.酸雨胁迫下,箬竹PSⅡ最大荧光(F_m)、最大光化学效率(F_v/F_m)、潜在活性(F_v/F_o)、有效光化学效率(F_v′/F_m′)、最大荧光产额(F_m′)、光化学淬灭系数(q_P)、非光化学淬灭系数(q_N)、PSII实际光化学效率(Φ_PSⅡ)降低,暗适应和光适应下的最小荧光产额F_o、F_o′ 则升高;而100 mg·L^-1硅预处理明显抑制了胁迫下各荧光参数的变化,F_v/F_m、F_v/F_o、F_v′/F_m′和Φ_PSⅡ分别增加35.2%、146.2%、55.0%和24.3%.说明外源适宜浓度硅预处理能有效地缓解酸雨胁迫导致的髯毛箬竹光合活性下降和光合系统损伤,从而提高胁迫下植物的光合能力.     

水淹对水芹叶片结构和光系统II光抑制的影响

通过探讨在水淹条件下水芹(Oenanthe javanica)叶片结构的变化以及出水对其光系统II功能和光抑制的影响, 阐明水芹光合机构在水淹条件下及出水后死亡的可能原因。结果表明: 水淹条件下新生沉水功能叶光系统II(PSII)最大光化学效率(Fv/Fm) 、电子传递活性与对照叶片差异很小, 但水淹使气生功能叶的Fv/Fm显著降低; 植株总生物量呈负增长趋势; 活体弱光条件下, 沉水叶出水后2小时叶片相对含水量(RWC)和Fv/Fm无显著变化; 中等光强和强光条件下其RWC和Fv/Fm迅速降低; 离体条件下, 5小时的中等光强对沉水叶的Fv/Fm影响不显著, 在随后的弱光下能恢复到出水时的初始状态; 强光能使沉水叶的Fv/Fm大幅降低, 且弱光下不能恢复到出水时的初始水平; 在解剖结构上, 水芹沉水叶的叶片总厚度、上下表皮厚度和气孔大小都显著低于气生叶, 而且沉水叶没有明显的栅栏组织分化, 但是沉水叶上表皮的气孔密度显著高于气生叶。研究结果表明, 水淹使水芹原气生叶PSII功能迅速衰退, 但对新生沉水叶片影响很小。水芹植株出水后, 沉水叶片结构变化使其在光下保水能力下降, 而强光导致了光合机构的光抑制和反应中心失活。田间条件下两者共同作用则加剧了对叶片光合机构的破坏, 进而致使其死亡。     

NO3-胁迫及恢复对黄瓜幼苗叶片叶绿素荧光参数及ATPase活性的影响

通过水培试验,探讨了不同NO₃^-浓度胁迫及恢复对黄瓜幼苗叶片叶绿素含量、叶绿素荧光参数及ATPase活性的影响.结果表明,胁迫7 d后,高浓度NO₃^-(168 mmol·L^-1)可极显著提高叶绿素a、叶绿素b、总叶绿素和类胡萝卜素含量,极显著提高初始荧光(F_o)、Mg ATPase和Ca-ATPase活性,而PSⅡ原初光能转化效率(F_v/F_m)、PSⅡ潜在活性(F_v/F_o)和PSⅡ光合电子传递量子效率(ΦPSⅡ),却随NO₃^-浓度的增加而降低.恢复7 d后,所有处理叶绿素和类胡萝卜素含量均低于对照;初始荧光基本都恢复至对照水平;PSⅡ原初光能转化效率和PSⅡ光合电子传递量子效率在NO₃^-浓度低于126 mmol·L^-1时,基本恢复至对照水平,而高于这一水平时,仍显著低于对照;PSⅡ潜在活性在NO₃^-浓度为42和126 mmol·L^-1的处理基本达对照水平,其它处理仍极显著低于对照;Mg-ATPase和Ca-ATPase活性均出现先降低后升高的变化趋势.     

Response of barley seedlings to UV-B radiation as affected by NaCl

The response of barley seedlings, subjected to 150 mmol/L NaCl for 4 days at different light regimes (4 d in the light, 4 d in darkness and a 12 h light/dark cycle) before UV-B radiation was investigated. NaCl treatment resulted in a decrease of total chlorophyll content and an increase in H2O2, free proline and lipid peroxidation, as quantified by measurement of malondialdehyde. Significantly more proline was accumulated in the light than in darkness. The combination of UV-B and NaCl treatment produced an additive effect on most of the parameters studied. UV-B radiation reduced the chlorophyll/carotenoids ratio and photochemical efficiency of PSII as estimated by chlorophyll fluorescence. NaCl pre-exposure decreased H2O2 generation and lipid peroxidation and alleviated the inhibitory effect of UV-B on PSII activity. Proline accumulated under salt stress conditions might be one of the reasons for the observed tolerance of barley seedlings to UV-B radiation.     

Effects of Enhanced UV-B Radiation on the Activity and Expression of Alternative Oxidase in Red Kidney Bean Leaves

An increase in ultraviolet （UV） B radiation on the earth＇s surface is a feature of current global climate changes. It has been reported that alternative oxidase （AOX） may have a protective role against oxidative stress induced by environmental stresses, such as UV-B. To better understand the characteristic tolerance of plants to UV-B radiation, the effects of enhanced UV-B radiation on the activity and expression of AOX in red kidney bean （Phaseolus vulgaris） leaves were investigated in the present study. The results show that the total respiration rate and AOX activity in red kidney bean leaves increased significantly during treatment with enhanced UV-B. However, cytochrome oxidase （COX） activity did not change significantly. The H2O2 content was also markedly increased and reached a maximum of 4.45 mmol·L^-1·g^-1 DW （dry weight） at 24 h of UV-B treatment, before dropping rapidly. Both alternative pathway content and alternative pathway activity were increased in the presence of exogenous H2O2. Immunoblotting analysis with anti-AOX monoclonal antibody revealed that expression of the AOX protein increased in red kidney bean leaves under enhanced UV-B radiation, reaching a peak at 72 h. In addition, AOX expression in red kidney bean leaves was induced by exogenous H2O2. These data indicate that the increase in AOX activity in red kidney bean leaves under enhanced UV-B radiation was mainly due to H2O2-induced AOX expression.     

Effects of Strong Light and Active Oxygen on Photosynthesis in Soybean

With the use of chlorophyll fluorescence technique, it was found that the net photosynthetic oxygen evolution rate decreased after strong light (2 000 μmol· m-2·2-1 ) treatment for two hours in soybean ( Glycine max L. ) leaves. The chlorophyll fluorescence parameters, Fm/Fo, Fv/Fm, ФPSII, qp and qN decreased along with the increase of light intensity. In strong light, exogenous active oxygen H202、·OH and 'O2 were harmful to soybean leaves. The destruction of 'O2 and·OH to leaves was most evident, as was shown that Fv/Fm and PS H decreased significantly. The antioxidants DABCO, mannitol, ascorbate and histidine protected the leaves, but weakly, from strong light. In darkness, the SOD inhibitor sodium diethyldithiocar- bamate (DDC) had no significant effect on Fm/Fo and Fv/Fm, but NAN,, the ascorbate peroxidase (APX)inhibitor, significantly decreased Fm/Fo, Fv/Fm and ФPS II. In strong light, however, beth DDC and NaN3 reduced the above-mentioned fluorescence parameters, but NaN3 was more effective than DDC. The results suggested that photoinhibition did take place in soybean leaves under strong light, and it was related to active oxygen in vivo.     

Effect of common bean seedling pretreatment with chlorocholine chloride on photosystem II tolerance to UV-B radiation,phytohormone content,and hydrogen peroxide content

In true leaves of common bean (Phaseolus vulgaris L., cv. Berbukskaya) 11-day-old seedlings, pretreatment with 1.6 mM chlorocholine chloride (CCC) resulted in the improved photosystem II (PSII) tolerance to UV-B radiation, an increase in the contents of cytokinins, ABA, and H₂O₂, but a decrease in the content of gibberellins. It is suggested that development of increased PSII tolerance to UV-B under the influence of CCC is partially related to the increase in the contents of ABA, cytokinins, and UV-absorbing pigments in the leaves of pretreated plants.     

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。     

增强UV-B辐射和SO2作用下植物光合响应及其相对抗性

 研究了20种野外生长的树种在增强UV-B、NaHSO3的作用下,它们的光合作用响应及其对这两种胁迫的抗性。研究结果表明,这些植物的抗性可分为抗性强、抗性中等和敏感3种类型。UV-B、NaHSO3以及UV-B+NaHSO3 3种处理与这些植物光合作用受抑制程度呈现良好的线性关系,说明这些植物在防御UV-B和NaHSO3伤害的能力方面有一致性,没有种的特异性。结果还表明,在这些植物中NaHSO3增强了UV-B对它们的抑制作用,敏感类型植物尤为明显。      

Response of photosynthetic apparatus in Arabidopsis thaliana L. mutant deficient in phytochrome A and B to UV-B

Photosynthetica - The effects of UV-B radiation (1 W m–2, 1 and 2 h) on PSII activity, chloroplast structure, and H2O2 contents in leaves of 26-d-old Arabidopsis thaliana phyA phyB double...     

Protection against photooxidative damage provided by enzymatic and non-enzymatic antioxidant system in sorghum seedlings

Effect of photoinhibition of sorghum leaves and isolated chloroplasts on chlorophyll fluorescence, peroxidation of thylakoid lipids and activity of antioxidant enzymes were studied. Photoinhibition of intact leaves and isolated chloroplasts decreased Fv/Fm ratio and qP, while qN increased. Photoinhibitory damage was more at 5 degrees C than at 30 degrees or 50 degrees C. Peroxidation of thylakoid lipids was 5 times greater when photoinhibited at 50 degrees C compared to control. Photoinhibition of chloroplasts under low oxygen condition or when supplemented with anti-oxidants (beta-carotene, ascorbate and GSH) resulted in significantly less damage to photosynthesis (Fv/Fm ratio) and peroxidation level. Photoinhibition also resulted in many fold increase in the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and decrease in catalase. Data presented here suggest that photoinhibition resulted in production of oxygen radicals and photoinhibition of chloroplasts in the presence of low oxygen level or when supplemented with antioxidants decreased the damage to Fv/Fm ratio and peroxidation level to a great extent since former prevented the formation of oxygen radicals and later could scavenge the oxygen radicals thus the protection. Increase activity of SOD and APX may also be to metabolise the oxygen radicals produced during photoinhibition treatment, thereby, protecting the seedlings against photooxidative damage.     

氧气在黑暗-水淹诱导植物叶片光合机构损伤中的作用

本研究排除了光照和根部信号的影响,在完全黑暗条件下对离体叶片进行水淹处理,并在处理过程中分别通入空气或者氮气来控制水淹过程中水中的含氧量。通过分析叶片叶绿素含量、活性氧含量以及叶片光化学活性的变化,探讨叶片水淹时水中缺氧因素对叶片光合机构的直接影响及作用机制。结果表明,与放置在湿润空气中的对照叶片相比,黑暗-水淹处理叶片的最大光化学效率（Fv/Fm）、捕获的激子将电子传递到QA以后的其他电子受体的概率（ψo）均发生显著下降。然而,黑暗．水淹处理36h后,叶片的叶绿素含量并未下降,叶片中H2O2含量也未大量增加。另外,黑暗一水淹导致的叶片光化学活性的下降随着水中含氧量下降的加剧而加剧,补充氧气可以缓解甚至消除这一伤害。这表明黑暗．水淹处理过程中叶片光合机构的伤害与叶片衰老或活性氧的积累无关,而是由于水中缺氧因素对光合机构的直接伤害所致。     

Protective Effect of Rare Earth Against Oxidative Stress Under Ultraviolet-B Radiation

The effects of lanthanum (III) (La(III)) in protecting soybean leaves against oxidative stress induced by ultraviolet-B (UV-B) radiation were investigated. The increase in contents of hydrogen peroxide (H₂O₂) and superoxide () due to UV-B radiation suggested oxidative stress. The increase in the content of malondialdehyde (MDA) and the decrease in the index of unsaturated fatty acid (IUFA) indicated oxidative damage on cell membrane induced by UV-B radiation. La(III) partially reversed UV-B-radiation-induced damage of plant growth. The reduction in the contents of H₂O₂, , and MDA and increase in the content of IUFA, compared with UV-B treatment, also indicated that La(III) alleviated the oxidative damage induced by UV-B radiation. The increase in the activities of superoxide dismutase and peroxidase and the contents of ascorbate, carotinoids, and flavonoids were observed in soybean leaves with La(III) + UV-B treatment, compared with UV-B treatment. Our data suggested that La(III) could protect soybean plants from UV-B-radiation-induced oxidative stress by reacting with reactive oxygen species directly or by improving the defense system of plants.     

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。     

Photoprotective Effects of D1 Protein Turnover and the Lutein Cycle on Three Ephemeral Plants under Heat Stress

To clarify the characteristics of photoinhibition and the primary defense mechanisms of ephemeral plant leaves against photodestruction under high temperature stress, inhibitors and the technology to determine chlorophyll fluorescence were used to explore the protective effects of D1 protein turnover and the lutein cycle in the high temperature stress of the leaves of three ephemeral plants. The results showed that the maximum light conversion efficiency (Fv/Fm) of the ephemeral plant leaves decreased, and the initial fluorescence (Fo) increased under 35°C ± 1°C heat stress for 1–4 h or on sunny days in the summer. Both Fv/Fm and Fo could be recovered after 8 h of darkness or afternoon weakening of the external temperature. Streptomycin sulfate (SM) or dithiothreitol (DTT) accelerated the decrease of Fv/Fm and the photochemical quenching coefficient (qP) in the leaves of three ephemeral plants at high temperature, and the decrease was greater in the SM than in the DTT treatment. When the high temperature stress was prolonged, the Y(II) values of light energy distribution parameters of PSII decreased, and the Y(NPQ) and Y(NO) values increased gradually in all the treatment groups of the three ephemeral plants. The results showed that the leaves of the three ephemeral plants had their own highly advanced mechanisms to protect against photodamage, which inhibited the turnover of D1 protein and xanthophyll cycle. This can damage the PSII reaction center in the leaves of the three ephemeral plants under high temperature. The protective effect of D1 protein turnover on heat stress in Erodium oxyrrhynchum and Senecio subdentatus was greater than that of the lutein cycle, while the protective effect of lutein cycle was greater than that of D1 protein turnover in Heliotropium acutiflorum subjected to heat damage.