Blue light is more essential than red light for maintaining the activities of photosystem Ⅱ and Ⅰ and photosynthetic electron transport capacity in cucumber leaves

Blue and red lights differently regulate leaf photosynthesis. Previous studies indicated that plants under blue light generally exhibit better photosynthetic characteristics than those under red light. However, the regulation mechanism of related photosynthesis characteristics remains largely unclear. Here, four light qualities treatments （300 μmol m-2 s-1） including white fluorescent light （FL）, blue monochromatic light （B, 440 nm）, red monochromatic light （R, 660 nm）, and a combination of red and blue light （RB, R：B=8：1） were carried out to investigate their effects on the activity of photosystem II （PSII） and photosystem I （PSI）, and photosynthetic electron transport capacity in the leaves of cucumber （Cucumis sativus L.） seedlings. The results showed that compared to the FL treatment, the R treatment significantly limited electron transport rate in PSII （ETR11） and in PSI （ETR1） by 79.4 and 66.3%, respectively, increased non-light induced non-photochemical quenching in PSII （q^No） and limitation of donor side in PSI （φND） and reduced most JIP-test parameters, suggesting that the R treatment induced suboptimal activity of photosystems and inhibited electron transport from PSII donor side up to PSI. However, these suppressions were effectively alleviated by blue light addition （RB）. Compared with the R treatment, the RB treatment significantly increased ETR, and ETR1 by 176.9 and 127.0%, respectively, promoted photosystems activity and enhanced linear electron transport by elevating electron transport from QA to PSI. The B treatment plants exhibited normal photosystems activity and photosynthetic electron transport capacity similar to that of the FL treatment. It was concluded that blue light is more essential than red light for normal photosynthesis by mediating photosystems activity and photosynthetic electron transport capacity.

Effects of drought treatment on photosystemⅡactivity in the ephemeral plant Erodium oxyrhinchum

Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas.Photosynthesis,one of the most important physiological processes of plants,can be significantly inhibited by drought.PhotosystemⅡ(PSⅡ)is considered the main attack target when photosynthesis is affected by drought.To clarify how PSⅡcomponents of the ephemeral plant Erodium oxyrhinchum(grown in the Gurbantunggut Desert,China)respond to drought treatment,we evaluated the functional activity of PSII by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels(control(400 mL),moderate drought(200 mL),and severe drought(100 m L)).Under moderate drought treatment,significant decreases were found in net photosynthetic rate(Pn),effective quantum yield of PSII(Y(Ⅱ)),relative electron transfer rate of PSII(rETR(Ⅱ)),oxygen-releasing complex,probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(Φ(E_(o))),probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(ψ(E_(o))),and performance index of PSⅡ(PI_(abs)).Compared to control treatment,marked increases were observed in water use efficiency(WUE),relative variable fluorescence at the J step(V_(J)),initial fluorescence(F_(o)),and dissipated energy per active reaction center(DI_(o)/RC)under moderate drought treatment,but there were no substantial changes in semi-saturated light intensity(I_(K)),active reaction centers per cross-section(RC/CS),and total performance index of PSII and PSI(PI_(total),where PSI is the photosystemⅠ).The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment.In addition,severe drought treatment significantly increased the absorbed energy per active reaction center(ABS/RC)and trapping energy per active reaction center(TR_(o)/RC)but decreased the energy transmission connectivity of PSⅡcomponents,RC/CS,and PI_(total),compared to moderate drought and control treatments.Principle component analysis(PCA)revealed similar information according to the grouping of parameters.Moderate drought treatment was obviously characterized by RC/CS parameter,and the values of F_(o),V_(J),ABS/RC,DI_(o)/RC,and TR_(o)/RC showed specific reactions to severe drought treatment.These results demonstrated that moderate drought treatment reduced the photochemical activity of PSII to a certain extent but E.oxyrhinchum still showed strong adaptation against drought treatment,while severe drought treatment seriously damaged the structure of PSⅡ.The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.

Plasticity of photorespiratory carbon concentration mechanism in Sedobassia sedoides(Pall.)Freitag&G.Kadereit under elevated CO_(2)concentration and salinity

Rising atmospheric CO_(2)(carbon dioxide)concentrations and salinization are manifestations of climate change that affect plant growth and productivity.Species with an intermediate C_(3)-C_(4)type of photosynthesis live in a wide range of precipitation,temperature,and soil quality,but are more often found in warm and dry habitats.One of the intermediate C_(3)-C_(4)photosynthetic type is C_(2)photosynthesis with a carbon concentration mechanism(CCM)that reassimilates CO_(2)released via photorespiration.However,the ecological significance under which C_(2)photosynthesis has advantages over C_(3)and C_(4)plants remains largely unexplored.Salt tolerance and functioning of CCM were studied in plants from two populations(P1 and P2)of Sedobassia sedoides(Pall.)Freitag&G.Kadereit Asch.species with C_(2)photosynthesis exposed to 4 d and 10 d salinity(200 mM NaCl)at ambient(785.7 mg/m^(3),aCO_(2)and elevated(1571.4 mg/m^(3),eCO_(2))CO_(2).On the fourth day of salinity,an increase in Na+content,activity catalase,and superoxide dismutase was observed in both populations.P2 plants showed an increase in proline content and a decrease in photosynthetic enzyme content:rubisco,phosphoenolpyruvate carboxylase(PEPC),and glycine decarboxylase(GDC),which indicated a weakening of C_(2)and C_(4)characteristics under salinity.Treatment under 10 d salinity led to an increased Na^(+)content and activity of cyclic electron flow around photosystem I(PSI CEF),a decreased content of K^(+)and GDC in both populations.P1 plants showed greater salt tolerance,which was assessed by the degree of reduction in photosynthetic enzyme content,PSI CEF activity,and changes in relative growth rate(RGR).Differences between populations were evident under the combination of eCO_(2)and salinity.Under long-term salinity and eCO_(2),more salt-tolerant P1 plants had a higher dry biomass(DW),which was positively correlated with PSI CEF activity.In less salt-tolerant P2 plants,DW correlated with transpiration and dark respiration.Thus,S.sedoides showed a high degree of photosynthetic plasticity under the influence of salinity and eCO_(2)through strengthening(P1 plants)and weakening C_(4)characteristics(P2 plants).

Cyclic electron flow around photosystem I is required for adaptation to high temperature in a subtropical forest tree, Ficus concinna

Dissipation mechanisms of excess photon energy under high-temperature stress were studied in a subtropical forest tree seedling, Ficus concinna. Net CO2 assimilation rate decreased to 16% of the control after 20 d high-temperature stress, and thus the absorption of photon energy exceeded the energy required for CO2 assimilation. The efficiency of excitation energy capture by open photosystem Ⅱ（PSⅡ） reaction centres （Fv＇/Fm＇） at moderate irradiance, photochemical quenching （qp）, and the quantum yield of PSII electron transport （φPSⅡ） were significantly lower after high-temperature stress. Nevertheless, non-photochemical quenching （qNP） and energy-dependent quenching （qE） were significantly higher under such conditions. The post-irradiation transient of chlorophyll （Chl） fluorescence significantly increased after the turnoff of the actinic light （AL）, and this increase was considerably higher in the 39 ℃-grown seedlings than in the 30 ~C-grown ones. The increased post-irradiation fluorescence points to enhanced cyclic electron transport around PSI under high growth temperature conditions, thus helping to dissipate excess photon energy non-radiatively.

Enhancement of Photophosphorylation and Photosynthesis in Rice by Low Concentrations of NaHSO_3 Under Field Conditions

Spraying 1-2 mmol/L solution of NaHSO 3 on rice ( Oryza sativa L.) leaves resulted in the enhancement of net photosynthetic rate for more than three days. It was also observed that NaHSO 3 application caused increases both in ATP content in leaves and the millisecond_delayed light emission of leaves. The increase in net photosynthetic rate caused by NaHSO 3 treatment was similar to that by PMS (phenazine methosulfate) treatment. The grain yield of treated rice was enhanced approximately by 10% after duplicated application of NaHSO 3 in milk_ripening stage. It is suggested that the enhancement of photosynthesis by NaHSO 3 treatment resulted from the effect of increasing ATP supplement. Concomitant with an increase in the photosynthetic rate and ATP content in leaves, the transient increase in chlorophyll fluorescence after the termination of actinic light, which could be used as an index of the cyclic electron flow, was also enhanced by low concentration of NaHSO 3 treatment. Basing on these results it is proposed that the increase in rice photosynthesis caused by low concentrations of NaHSO 3 could be due to the stimulation of the cyclic electron flow around PSⅠ which in turn the enhancement of the coupled photophosphorylation and photosynthesis.

Contribution of Cyclic and Pseudo-cyclic Electron Transport to the Formation of Proton Motive Force in Chloroplasts

Photosynthetic electron transport is coupled to proton translocation across the thylakoid membrane, re- sulting in the formation of a trans-thylakoid proton gradient （△pH） and membrane potential （△ψ）. Ion trans-porters and channels localized to the thylakoid membrane regulate the contribution of each component to the proton motive force （pmf）. Although both △pH and △ψ contribute to ATP synthesis as pmf, only ~pH downregulates photosynthetic electron transport via the acidification of the thylakoid lumen by inducing thermal dissipation of excessive absorbed light energy from photosystem II antennae and slowing down of the electron transport through the cytochrome bsf complex. To optimize the tradeoff between efficient light energy utilization and protection of both photosystems against photodamage, plants have to regulate the pmf amplitude and its components, △pH and △ψ. Cyclic electron transport around photosystem I （PSI） is a major regulator of the pmf amplitude by generating pmf independently of the net production of NADPH by linear electron transport. Chloroplast ATP synthase relaxes pmf for ATP synthesis, and its activity should be finely tuned for maintaining the size of the pmf during steady-state photosynthesis. Pseudo-cyclic electron transport mediated by flavodiiron protein （FIv） forms a large electron sink, which is essential for PSI photoprotection in fluctuating light in cyanobacteria. FIv is conserved from cyanobacteria to gymno- sperms but not in angiosperms. The Arabidopsis proton gradient regulation 50（pgr5） mutant is defective in the main pathway of PSI cyclic electron transport. By introducing Physcomitrella patens genes encoding Flvs, the function of PSI cyclic electron transport was substituted by that of FIv-dependent pseudo-cyclic electron transport. In transgenic plants, the size of the pmf was complemented to the wild-type level but the contribution of △pH to the total pmf was lower than that in the wild type. In the pgr5 mutant, the size of the pmf was drastically lowered by the absence of PSI cyclic electron transport. In the mutant, △pH occupied the majority ofpmf, suggesting the presence of a mechanism for the homeostasis of luminal pH in the light. To avoid damage to photosynthetic electron transport by periods of excess solar energy, plants employ an intricate regulatory network involving alternative electron transport pathways, ion transporters/channels, and pH-dependent mechanisms for downregulating photosynthetic electron transport.

光温逆境下扬麦158旗叶PSI颗粒特性的变化

研究了光温逆境对扬麦 １５８ 旗叶 Ｐ Ｓ Ｉ颗粒光化学特性和多肽组分的影响．电子传递活性的结果表明：光温逆境（２５００ μｍ ｏｌ／ｍ ２ｓ，３７℃）条件下，扬麦 １５８ Ｐ Ｓ Ｉ颗粒还原能力产生明显下降； Ｐ Ｓ Ｉ颗粒多肽组分中，受体端１９０００、 Ｌ Ｃ Ｈ Ｉ及作用中心的部分小分子多肽对光温逆境反应较为敏感，降解最为显著．光温逆境条件下 Ｌ Ｈ Ｃ Ｉ在维持 Ｐ Ｓ

棉花花铃期低温对叶片PSI和PSII光抑制的影响

选用陆地棉(Gossypium hirsutum L.)品种新陆早45号,在室外盆栽至开花结铃期后,移至人工气候室,模拟新疆棉花花铃期易出现的低温逆境条件,设置处理T(16℃/10℃,昼/夜),以常温(30℃/18℃,昼/夜)处理作为对照,采用叶绿素荧光和P700同步测定技术,研究低温对棉花花铃期叶片光合机构PSII能量分配、PSI氧化还原状态及环式电子传递流的影响。结果表明,与对照相比,低温处理显著降低了棉花叶片PSII光适应状态下最大光化学量子产量(F_v'/F_m')、光化学猝灭系数(qP)和PSII有效光化学量子产量[Y(II)],并使PSII非调节性能量耗散[Y(NO)]和调节性能量耗散[Y(NPQ)]量子产量显著升高,诱导PSII发生光抑制。低温引起棉花叶片光合机构PSI受体侧限制[Y(NA)]显著下降和供体侧限制[Y(ND)]显著升高,但未引起有效的PSI复合体含量(P_m)显著降低,表明与PSII相比,棉花叶片PSI对低温不敏感。此外,低温引起环式电子传递量子产量[Y(CEF)]以及与PSII实际量子产量比率的[Y(CEF)/Y(II)]显著升高,进一步表明在低温下,光破坏防御机制中环式电子传递流对棉花PSI、PSII起着重要的保护作用,是主要的光破坏防御机制。非光化学热耗散(NPQ)和调节性非光化学热耗散[Y(NPQ)]与[Y(CEF)]具有显著的正相关关系,表明低温引起棉花花铃期叶片PSII反应中心过度关闭产生过剩的激发能,造成了PSII可逆的光抑制,环式电子传递流的响应及较高的调节性能量耗散共同保护了棉花叶片PSI和PSII免受光抑制的损伤,这可能是棉花叶片PSI对低温不敏感的重要原因。

PGR5-PGRL1-Dependent Cyclic Electron Transport Modulates Linear Electron Transport Rate in Arabidopsis thaliana

Plants need tight regulation of photosynthetic electron transport for survival and growth under environ- mental and metabolic conditions. For this purpose, the linear electron transport （LET） pathway is supple- mented by a number of alternative electron transfer pathways and valves. In Arabidopsis, cyclic electron transport （CET） around photosystem I （PSI）, which recycles electrons from ferrodoxin to plastoquinone, is the most investigated alternative route. However, the interdependence of LET and CET and the relative importance of CET remain unclear, largely due to the difficulties in precise assessment of the contribution of CET in the presence of LET, which dominates electron flow under physiological conditions. We there- fore generated Arabidopsis mutants with a minimal water-splitting activity, and thus a low rate of LET, by combining knockout mutations in Psb01, PsbP2, PsbQ1, PsbQ2, and PsbR loci. The resulting 45 mutant is viable, although mature leaves contain only ~20% of wild-type naturally less abundant Psb02 protein. 45 plants compensate for the reduction in LET by increasing the rate of CET, and inducing a strong non-photochemical quenching （NPQ） response during dark-to-light transitions. To identify the molecular origin of such a high-capacity CET, we constructed three sextuple mutants lacking the qE component of NPQ （45 npq4-1）, NDH-mediated CET （45 crr4-3）, or PGR5-PGRLl-mediated CET （45 pgrS）. Their analysis revealed that PGR5-PGRLl-mediated CET plays a major role in ~pH formation and induction of NPQ in C3 plants. Moreover, while pgr5 dies at the seedling stage under fluctuating light conditions, 45 pgr5 plants are able to survive, which underlines the importance of PGR5 in modulating the intersystem electron transfer.

Far-red light: A regulator of plant morphology and photosynthetic capacity

Plant photosynthetic capacity directly determines crop yield. Light quality regulates photosynthetic capacity. This review discusses plant responses to far-red light from the phenotypic to the molecular level, focusing specifically on the improvement of photosynthetic capacity by adjustment of photosynthetic electron transport and the path of light energy. Far-red light can also regulate leaf angle and increase plant height and leaf area, via expression of associated genes, to capture more light energy.Thus, far-red light regulates plant morphology and photosynthetic capacity. Identifying the mechanism of this regulation may lead to increased crop yields.

Pyropia yezoensis can utilize CO_2 in the air during moderate dehydration

Pyropia yezoensis, an intertidal seaweed, experiences regular dehydration and rehydration with the tides. In this study, the responses of P. yezoensis to dehydration and rehydration under high and low CO2 concentrations （（600-700）×10^-6 and （40-80）×10^-6, named Group I and Group II respectively） were investigated. The thalli of Group I had a significantly higher effective photosystem II quantum yield than the thalli of Group II at 71% absolute water content （AWC）. There was little difference between thalli morphology, total Rubisco activity and total protein content at 100% and 71% AWC, which might be the basis for the normal performance of photosynthesis during moderate dehydration. A higher effective photosystem I quantum yield was observed in the thalli subjected to a low CO2 concentration during moderate dehydration, which might be caused by the enhancement of cyclic electron flow. These results suggested that P. yezoensis can directly utilize COz in ambient air during moderate dehydration.

植物光系统Ⅱ(PSⅡ)应答非生物胁迫机理研究进展

植物生长过程受到一系列以环境因子(温度、干旱、盐和重金属等)为代表的非生物胁迫影响,进而阻碍以物质转化与能量代谢等为主要特征的光合进程。光系统Ⅱ(PSⅡ)是位于类囊体膜上的多亚基色素-蛋白质复合物,通过捕获光能完成水的光解和质体醌的还原,对植物生长发育尤为重要。一般来说,非生物胁迫会抑制PSⅡ的活性、影响PSⅡ的结构、阻碍电子传递和能量转换,而PSⅡ作为光合作用中最易受影响的部分,近年来与环境因子之间的关系备受关注。基于此,本文对主要非生物胁迫如温度、干旱、盐,以及重金属下植物PSⅡ的生理应答研究进行了归纳,并基于叶绿素荧光技术从PSⅡ的结构与功能、电子传递过程、光抑制与光保护等方面进行了综述。并对现有研究的不足提出了展望,为今后深入研究非生物胁迫下植物PSⅡ响应逆境胁迫过程中的生理与分子机制提供理论基础。

The response of electron transport mediated by active NADPH dehydrogenase complexes to heat stress in the cyanobacterium Synechocystis 6803

The electron-transport machinery in photosynthetic membranes is known to be very sensitive to heat. In this study, the rate of electron transport (ETR) driven by photosystem I (PSI) and photosystem II (PSII) during heat stress in the wild-type Synechocystis sp. strain PCC 6803 (WT) and its ndh gene inactiva-tion mutants △ndhB (M55) and △ndhD1/ndhD2 (D1/D2) was simultaneously assessed by using the novel Dual-PAM-100 measuring system. The rate of electron transport driven by the photosystems (ETRPSs) in the WT, M55, and D1/D2 cells incubated at 30℃ and at 55℃ for 10 min was compared. Incubation at 55 ℃ for 10 min significantly inhibited PSII-driven ETR (ETRPSII) in the WT, M55 and D1/D2 cells, and the ex-tent of inhibition in both the M55 and D1/D2 cells was greater than that in the WT cells. Further, PSI-driven ETR (ETRPSI) was stimulated in both the WT and D1/D2 cells, and this rate was increased to a greater extent in the D1/D2 than in the WT cells. However, ETRPSI was considerably inhibited in the M55 cells. Analysis of the effect of heat stress on ETRPSs with regard to the alterations in the 2 active NDH-1 complexes in the WT, M55, and D1/D2 cells indicated that the active NDH-1 supercomplex and medi-umcomplex are essential for alleviating the heat-induced inhibition of ETRPSII and for accelerating the heat-induced stimulation of ETRPSI, respectively. Further, it is believed that these effects are most likely brought about by the electron transport mediated by each of these 2 active NDH-1 complexes.

Binding Model and 3D-QSAR of 3-（2-Chloropyrid-5- ylmethylamino）-2-cyanoacrylates as PSⅡ Electron Transport Inhibitor

The binding model of 3-（2-chloropyrid-5-ylmethylamino）-2-cyanoacrylate photosystem Ⅱ （PSⅡ） electron transport inhibitors with the D 1 protein of PSII was built. The high herbicidal activity of this kind of inhibitors was explained by docking studies： in addition to usual factors, the N atom on the pyridine ring could form an H-bond with the backbone amide of Phe265 on the D1 protein. 3D-QSAR analysis on sixteen 3-（2-chloropyrid-5-yl- methylamino）-2-cyanoacrylate compounds was performed using CoMFA method to explain the nature of interactions between the compounds and D1 protein. These studies may provide useful insights for designing new PSII electron transport inhibitors.

盐胁迫对不同倍性金银花光合特性的影响

【目的】研究四倍体和二倍体金银花叶片光合作用对盐胁迫的响应,特别是盐胁迫对PSⅠ和PSⅡ性能以及协调性的影响,比较盐胁迫下叶片光合特性的差异,分析盐胁迫对叶片Na+、Cl-和丙二醛含量以及叶片生物量的影响,揭示不同倍性金银花耐盐胁迫的能力,为盐碱地栽培品种的选择提供参考。【方法】选用四倍体和二倍体金银花为试验材料,采用叶绿素荧光快速诱导动力学曲线和820 nm光反射曲线同步测定技术,结合气体交换参数,研究中度(150 mmol·L-1 Na Cl)和重度(300 mmol·L-1 Na Cl)盐胁迫对四倍体和二倍体金银花叶片光合作用和光合机构的影响。金银花植株定植于装有石英砂的塑料盆中,Hoagland营养液培养。营养液中加入Na Cl用于盐处理,每天递增50 mmol·L-1到达处理浓度(150和300 mmol·L-1),处理持续15 d。以不加入Na Cl的营养液培养对照植株。盐处理过程中选取枝条中部全展的叶片用于指标测定。【结果】中度盐胁迫下,四倍体和二倍体金银花叶片光合速率、气孔导度和胞间CO2浓度显著降低,但四倍体下降幅度小于二倍体,说明中度盐胁迫下光合速率的降低是由气孔限制引起的,四倍体叶片光合作用受气孔限制程度较小。重度盐胁迫下,四倍体和二倍体金银花叶片光合速率也显著降低,但四倍体下降幅度小于二倍体,能维持较高的光合活性。重度盐胁迫7 d后,二倍体金银花叶片Rubisco酶的活化状态和羧化效率显著降低,诱发PSⅡ光抑制,降低向PSⅠ电子传递的量子产额。因此,PSⅠ的还原受到抑制,820 nm光反射曲线应该显示PSⅠ氧化幅度增加。但结果相反,PSⅠ氧化幅度却显著降低。重度盐胁迫下,二倍体金银花叶片PSⅠ也发生了光抑制,不能有效推动电子向PSⅠ受体侧传递,抑制了PSⅠ的氧化,而PSⅠ光抑制程度高于PSⅡ,导致PSⅠ氧化幅度显著降低,破坏了PSⅡ与PSⅠ的协调性。重度盐胁迫15 d后,四倍体金银花叶片Rubisco酶活化状态和羧化效率显著下降,但下降幅度小于二倍体金银花,PSⅡ和PSⅠ的性能未受显著影响,维持了PSⅡ和PSⅠ的协调性。因此,相对于二倍体,四倍体金银花叶片在重度盐胁迫下也具有较高的光合活性。盐胁迫15 d后,二倍体金银花叶片Na+、Cl-和丙二醛含量显著增加,整株叶片干重显著降低,其变化幅度大于四倍体金银花,说明四倍体金银花受离子毒害的影响较轻,这可能是其在盐胁迫下维持较高光合性能的原因。【结论】盐胁迫下,四倍体金银花叶片能维持较高的气孔导度和Rubisco酶的活化状态,保持了PSⅡ和PSⅠ的协调性,因而具有较高的光合活性,能够积累较多的生物量。因此,四倍体金银花耐盐胁迫的能力强于二倍体,更适于盐碱地栽培。

低温对水稻幼苗叶绿体光化学功能及类囊体膜蛋白水平的影响

研究了低温胁迫下水稻幼苗叶绿体光合电子传递功能及类囊体膜蛋白水平的变化。４℃低温结合３５μｍｏｌ／（ｍ２·ｓ）的弱光照处理，使水稻叶绿体全电子链、ＰＳⅡ和ＰＳⅠ的电子传递活性均降低，降低的幅度依次是：全电子链＞ＰＳⅡ＞ＰＳⅠ。对类囊体膜蛋白组分进行的ＳＤＳ－ＰＡＧＥ分析显示，低温使大部分类囊体膜蛋白特别是ＰＳⅡ功能蛋白的稳态水平降低，这可能是造成叶绿体光化学功能降低的主要原因。进一步对低温影响ＰＳⅡ电子传递活性的机理进行了探讨，所得结果表明，低温下ＰＳⅡ功能受抑的主要原因是其氧化侧的电子供应受阻，而与反应中心受到的伤害关系不大，尽管类囊体膜的ＳＤＳ－ＰＡＧＥ结果显示ＰＳⅡ的反应中心也受到低温的损伤。

2-氰基-3-取代吡啶甲胺基-3-取代丙烯酸乙氧乙酯的合成和除草活性研究

一系列2-氰基-3-取代吡啶甲胺基丙烯酸酯被合成作为光合作用光系统II电子传递抑制剂.生测发现一些目标化合物表现出很好的除草活性,如(Z)-2-氰基-3-异丙基-3-(2-烷氧基取代的吡啶-3-基)甲胺基丙烯酸乙氧乙酯.生测结果表明在吡啶环的2位合适的取代基和丙烯酸酯的3位取代基的体积对除草活性至关重要.

B型烟粉虱危害对烟草叶片光系统Ⅱ的影响

【目的】研究B型烟粉虱取食危害对烟草光系统Ⅱ的影响,为明确烟粉虱对寄主植物光合作用的影响机制提供依据。【方法】通过测定烟草叶片叶绿素荧光快速诱导曲线,使用JIP-test分析技术进行参数分析,研究B型烟粉虱危害烟草后对烟草的局部虫体叶和系统叶光系统Ⅱ(PSII)的影响。【结果】B型烟粉虱危害烟草后虫体叶和系统叶上的最大光化学效率(φpo)和光化学性能指数(PIABS)与对照相比均明显升高(P<0.05),表明处理烟草植株的局部叶和系统叶的原初光化学反应受到较大的伤害。B型烟粉虱危害烟草后虫体叶和系统叶PSII反应中心的电子传递均受阻,放氧复合体受到严重破坏。B型烟粉虱危害烟草后系统叶的单位反应中心吸收的能量(ABS/RC)和单位反应中心热耗散掉的能量(DIo/RC)增加,单位反应中心捕获的能量(TRo/RC)下降;B型烟粉虱危害的虫体叶中ABC/RC没有变化,DIo/RC增加,TRo/RC下降。B型烟粉虱危害烟草后虫体叶和系统叶的单位面积反应中心数量(RC/CS)均明显降低(P<0.05),而光系统PSⅡ反应中心的关闭程度(1-qP)却明显升高,分别较各自对照升高了69.83%和142.58%(P<0.05)。【结论】B型烟粉虱的危害严重影响了烟草叶片的光系统Ⅱ(PSII),主要是由于PSII反应中心的失活和关闭以及对PSII电子传递的抑制,电子传递中受抑制的位点包括放氧复合体和QA到QB间的电子传递过程,同时B型烟粉虱危害影响了烟草叶片光系统的能量流动,且烟粉虱对烟草叶片PSII的影响具有系统传导性。

链格孢菌毒素对莱茵藻光合电子传递的抑制及其作用位点

以野生型莱茵藻和其抗除草剂突变体为材料,检测链格孢菌毒素在光合电子传递链上的作用位点和模式的结果表明,此种毒素抑制Q_A至Q_B的电子传递,是光系统Ⅱ抑制剂,其作用模式类似于苯酚类型的除草剂。

脓青素对光抑制条件下菠菜叶绿体的保护作用

在有氧条件下，脓青素可以缓解强光对菠菜叶绿体电子传递的抑制作用。加入解联剂尼日利亚菌素消除跨膜质子梯度会加剧叶绿体的光抑制，但脓青素的保护作用并不消失。脓青素对光系统Ⅰ与光系统Ⅱ均表现出保护作用，但对ＰＳⅡ的保护在光抑制初期较明显；在厌氧条件下，脓青素加剧叶绿体的光抑制，引起ＤＣＩＰ光还原与水到ｐ－ＢＱ电子传递活力的降低。推测脓青素可能通过促进细胞色素ｂ５５９介导的ＰＳⅡ循环电子传递，减轻了叶绿体的光抑制。