LHCII is a crucial light-harvesting pigment/protein complex in photosystem II (PSII) supercomplex. It also participates in the light energy redistribution between photosystems and in the photoprotection via its revers...LHCII is a crucial light-harvesting pigment/protein complex in photosystem II (PSII) supercomplex. It also participates in the light energy redistribution between photosystems and in the photoprotection via its reversible dissociation with PSII and PSI (photosystem I). This reversible detachment of LHCII is regulated by phosphorylation of its own and PSII core protein. Under low light conditions, LHCII is phosphorylated and dissociated with PSII core protein complex and combined with PSI, which balances the excitation energy between PSII and PSI;Under high light environment, the phosphorylation of PSII core proteins makes LHCII detach from PSII. The dissociated LHCII presents in a free state, which involves in the thermal dissipation of excess excitation energy. During photodamage, dual phosphorylations of both PSII core proteins and LHCII complexes occur. The phosphorylation of D1 is conductive to the disintegration of photodamaged PSII and the cycle of repair. In this circumstance, the phosphorylation of LHCII is induced by reactive oxygen species (ROS) and then the phosphorylated LHCII migrates to PSI, into the repair cycle of damaged PSII. The ferredoxin (Fdr) and thioredoxin (Tdr) system may play a possible central role in the phosphorylation regulation on LHCII dissociation.展开更多
Malate is the first stable product after CO2 is fixed in NADP-dependent malic enzyme (NADP-ME) type of C4 plants, which transfers CO2 and the reducing equivalent from mesophyll cell (MC) to vascular bundle sheath cell...Malate is the first stable product after CO2 is fixed in NADP-dependent malic enzyme (NADP-ME) type of C4 plants, which transfers CO2 and the reducing equivalent from mesophyll cell (MC) to vascular bundle sheath cell (BSC) chloroplasts and affects the redox state of BSC. The aim of this experiment is to investigate the effect of exogenous malate on the activity of photosystem II (PS II) in C4 and C3 plants. The leaf discs from the 5th fully expanded leaves of maize (NADP-ME type C4 plants) and the 10th fully expanded leaves of tobacco (C3 plants) were treated with malate of 50, 100 μM and the chlorophyll fluorescence parameters were measured. Malate treatments decreased the photochemical reaction efficiency (FV/FM) in maize leaves, as a result of rising in initial fluorescence (FO) and decreasing in maximal fluorescence (FM). The number of active PS II reaction center (RC) per excited cross section (RC/CS) declined in malate-treated maize, suggesting that malate inactivated PS II RC. Malate treatments also increased Wk, representing the severity of oxygen-evolving complex (OEC) damage, and decreased the rate of photosynthetic oxygen evolution. We conclude that exogenous malate regulates the activity and structure of PS II in C4 plant maize. No significant changes in the activity of PS II were observed in malate-treated C3 plant tobacco. It is suggested that the short term malate treatment will inhibit PS II of leaves which have C4 anatomy and C4 enzymes.展开更多
Because the transient O3 injury of leaves is lost with time, the evaluation of O3 effect on the maximum quantum efficiency of PSII (Fv/Fm) is difficult. Thus, the authors examined Fv/Fm in rice leaves exposed to diffe...Because the transient O3 injury of leaves is lost with time, the evaluation of O3 effect on the maximum quantum efficiency of PSII (Fv/Fm) is difficult. Thus, the authors examined Fv/Fm in rice leaves exposed to different O3 concentrations (0, 0.1, and 0.3 cm3·m-3, expressed as O0, O0.1, and O0.3) under different dark adaptation periods (0, 1, 5, 10, 20, and 30 min, expressed as D0, D1, D5, D10, D20, and D30) to ascertain its optimum time span. Fv/Fm was inhibited by O3;however in the O0 and O0.1 plants, it recovered during dark adaptation. In the O0.3 plants, Fv/Fm decreased gradually with time. F0 was found to be increased by O3, and it increased further in the O0.3 plants during dark adaptation. Under a high light intensity, Fm was decreased by O3, and the O3-induced damage to Fv/Fm was therefore more pronounced. However, the sensitivity of展开更多
The deleterious effects of ultraviolet B(UV-B)radiation on photosynthesis and photosynthetic proteins of tropical and temperate plants have been studied.Like tropical plants(black gram and green gram),the temperate pl...The deleterious effects of ultraviolet B(UV-B)radiation on photosynthesis and photosynthetic proteins of tropical and temperate plants have been studied.Like tropical plants(black gram and green gram),the temperate plants(carrot and radish)also successfully grown in the tropical region.They were exposed to enhanced UV-B radiation under field condition.Comparative studies show that under enhanced UV-B radiation photosynthetic activity was increased in black gram.In green gram and radish the UV-B radiation slightly enhanced the photosynthetic activity,but it inhibited the photosynthetic activity in carrot.The comparative results showed changes in contents of thylakoid 55,47,43,33,29,27-25,23 and 17 kDa polypeptides that were significantly lowered in UV-B treated carrot plant when compared to other plants.The PSII protein profile results showed a strong correlation between the presence of a membrane polypeptide and photosynthetic activity.In black gram and green gram the UV-B radiation did not produce any significant difference in the PSII polypeptides.As in the case of radish the UV-B radiation increased the accumulation of 33-28 kDa protein and affected expression of the 63 kDa protein.In the case of carrot,severe degradation of 32 kDa and 33 kDa,corresponding to D1 and D2 core proteins of PSII,was observed.It could be concluded that the ability of plants to tolerate increased levels of UV-B radiation,relative to photosynthetic capacity,depends on acclimation processes of the plant in the growing region.展开更多
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 inhibite...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.展开更多
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 re...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.展开更多
The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated with spinach thylakoids, phycobiliproteins isolated from red and blue- green algae transferred ...The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated with spinach thylakoids, phycobiliproteins isolated from red and blue- green algae transferred light energy absorbed to spinach PSII. The efficiency of energy transfer was dependent on the kind of phycobiliproteins used. If spinach thylakoids were replaced by the thylakoids of Brassica chinensis, R phycoerythin or C- phycocyanin did not transfer their excitation energy to PSII of Brassica chinensis unless allophycocyanin was present.展开更多
To investigate the effect of reduced salinity on diatoms’ capacity to cope with changing ultraviolet radiation(U VR) and photosynthetically active radiation(PAR),Skeletonema costatum was grown in a range of salinity(...To investigate the effect of reduced salinity on diatoms’ capacity to cope with changing ultraviolet radiation(U VR) and photosynthetically active radiation(PAR),Skeletonema costatum was grown in a range of salinity(15,25,and 35).The photo system Ⅱ(PSⅡ) function was analyzed by increasing PAR and UVR to mimic a mixing event in turbulent waters.The re sults show that high UVR exposure significantly reduced PSII activity,especially in cells grown at low salinity.UVR,but not salinity,stimulated the ’removal’ rate of PSII protein PsbA.Salinity alone,in the range of 15 to 35,did not regulate PSⅡ acceptor region;however,the low salinity+UVR treatment decreased the energy flux for electron transport per PSⅡ reaction center in S.costatum.It showed that low salinity exacerbated the damaging effect of UVR on PSⅡ function in S.costatum by suppressing Psb A protein synthe sis and modifying the photochemistry of PSⅡ.Although higher catalase(CAT) activity and NPQs were induced,they were unable to prevent the combined damage effect of low salinity+UVR.Our findings indicate that reduced salinity and increased UVR potentially affect the abundance and distribution of S.costatum with the escalation of climate disturbances.展开更多
Nutrient enrichment experiments with nitrogen （N） and phosphorus （P） were conducted with samples from two stationsin the coastal waters of Qingdao, China, during summer to identify limiting nutrients. In late July...Nutrient enrichment experiments with nitrogen （N） and phosphorus （P） were conducted with samples from two stationsin the coastal waters of Qingdao, China, during summer to identify limiting nutrients. In late July of 2009, low P concentrations andthe maximum photochemical efficiency of photosystem II （Fv/Fm） in the initial samples together with Fv/Fm and chlorophyll a （Chl a）responses to P addition indicated P limitation at the two stations. In early August, low P levels still limited phytoplankton growth atstation A. Fv/Fm and Chl a were the highest in the NP treatments at station B, suggesting an N/P co-limitation. In mid-September,nutrient concentrations and Fv/Fm were elevated and phytoplankton communities were healthy. Greater Fv/Fm and Chl a in the treat-ments with added P than those without the addition suggested potential P limitation at station A. Lack of Fv/Fm and Chl a responsesfollowing nutrient additions indicated N and P repletion at station B. At the end of July 2010, neither N nor P was limited at station B.Additionally, Fv/Fm coupled with 24-h-long nutrient enrichment experiments can be used to detect P limitation and N/P co-limitationto natural populations. This method can be more accurate for assessing co-limitation than the use of criteria of nutrient concentrationsand ratios as indicators, and can provide more rapid results than nutrient addition bioassays using chlorophyll response as an indica-tor, when a population is potentially limited. Compared with the two conventional methods, the results based on F,/F~ can also pro-vide more detailed information about physiological states of the populations.展开更多
[Objective] The paper was to investigate effects of glyphosate stress on physiological characteristics and protein expression of photosystem Ⅱ(PSⅡ) in genentically modified soybean GTS 40-3-2 seedlings under severe ...[Objective] The paper was to investigate effects of glyphosate stress on physiological characteristics and protein expression of photosystem Ⅱ(PSⅡ) in genentically modified soybean GTS 40-3-2 seedlings under severe drought condition. [Method] A pot experiment was carried out in growth chamber to determine the response of genetically modified soybean treated by severe drought stress and different concentrations of glyphosate at the third compound leaf stage. [Result] Severe drought treatment increased the electrolyte leakage(EL), superoxide dismutase(SOD) and peroxidase(POD) activities, and decreased the relative water content(RWC), chlorophyll content, and catalase(CAT) activity. The EL, SOD and POD activities were significantly increased in severe drought and glyphosate treatments, which were related to glyphosate concentrations. The chlorophyll content decreased, which was also related to glyphosate concentrations. But the BWC and CAT activity were not affected by glyphosate concentrations. Western blot displayed that PSⅡ protein Lhcb2 was not affected by stress conditions and stably expressed. D1, D2 and Lhcb4 protein level decreased, and there was no significant change in Lhcb1 expression under severe drought stress. The protein levels of D1, D2, Lhcb1 and Lhcb4 decreased with the increase of glyphosate concentrations under severe drought and glyphosate stress. When the glyphosate concentrations were 0.92 and 1.84 kg·ai/hm^2, the protein levels of D1, D2 and Lhcb4 were slightly higher than those in severe drought stress. When the glyphosate concentrations were 3.68 and 7.36 kg·ai/hm^2, the protein level of D1, D2, Lhcb1 and Lhcb4 decreased sharply. [Conclusion] This research provides a theoretical basis for production of genetically modified soybean.展开更多
With global warming, high-temperature(HT) stress has become a major abiotic stress for crops, in particular summer maize in China. Photosynthesis is sensitive to HT. Salicylic acid(SA) and 6-benzyladenine(6-BA) can im...With global warming, high-temperature(HT) stress has become a major abiotic stress for crops, in particular summer maize in China. Photosynthesis is sensitive to HT. Salicylic acid(SA) and 6-benzyladenine(6-BA) can improve the adaptation of plants to various biotic and abiotic stresses. However, their contribution to maintaining photosynthetic activity and alleviating photoinhibition in maize leaves under HT stress is still unclear. The effects of exogenous SA or 6-BA on growth, photosynthesis capacity, photosystem Ⅱ(PSII) activity, subcellular ultrastructure, antioxidant system, and plant hormones in maize leaves under HT stress were investigated. Under HT conditions, application of SA or 6-BA up-regulated gibberellin and zeatin content in leaves, increasing leaf area index(LAI). It also expanded the stomata by reducing abscisic acid and jasmonic acid content in leaves, cooling them and increasing CO2supply to photosynthesis. A higher net photosynthetic rate, combined with increased activity of the antioxidant system, alleviated oxidative stress in maize plants sprayed with SA or 6-BA, allowing them to maintain their chloroplast ultrastructure and PSII activity, in particular electron transfer from QAto QB. The increased LAI and net photosynthetic rate per unit leaf area also resulted in the accumulation of more biomass.展开更多
文摘LHCII is a crucial light-harvesting pigment/protein complex in photosystem II (PSII) supercomplex. It also participates in the light energy redistribution between photosystems and in the photoprotection via its reversible dissociation with PSII and PSI (photosystem I). This reversible detachment of LHCII is regulated by phosphorylation of its own and PSII core protein. Under low light conditions, LHCII is phosphorylated and dissociated with PSII core protein complex and combined with PSI, which balances the excitation energy between PSII and PSI;Under high light environment, the phosphorylation of PSII core proteins makes LHCII detach from PSII. The dissociated LHCII presents in a free state, which involves in the thermal dissipation of excess excitation energy. During photodamage, dual phosphorylations of both PSII core proteins and LHCII complexes occur. The phosphorylation of D1 is conductive to the disintegration of photodamaged PSII and the cycle of repair. In this circumstance, the phosphorylation of LHCII is induced by reactive oxygen species (ROS) and then the phosphorylated LHCII migrates to PSI, into the repair cycle of damaged PSII. The ferredoxin (Fdr) and thioredoxin (Tdr) system may play a possible central role in the phosphorylation regulation on LHCII dissociation.
文摘Malate is the first stable product after CO2 is fixed in NADP-dependent malic enzyme (NADP-ME) type of C4 plants, which transfers CO2 and the reducing equivalent from mesophyll cell (MC) to vascular bundle sheath cell (BSC) chloroplasts and affects the redox state of BSC. The aim of this experiment is to investigate the effect of exogenous malate on the activity of photosystem II (PS II) in C4 and C3 plants. The leaf discs from the 5th fully expanded leaves of maize (NADP-ME type C4 plants) and the 10th fully expanded leaves of tobacco (C3 plants) were treated with malate of 50, 100 μM and the chlorophyll fluorescence parameters were measured. Malate treatments decreased the photochemical reaction efficiency (FV/FM) in maize leaves, as a result of rising in initial fluorescence (FO) and decreasing in maximal fluorescence (FM). The number of active PS II reaction center (RC) per excited cross section (RC/CS) declined in malate-treated maize, suggesting that malate inactivated PS II RC. Malate treatments also increased Wk, representing the severity of oxygen-evolving complex (OEC) damage, and decreased the rate of photosynthetic oxygen evolution. We conclude that exogenous malate regulates the activity and structure of PS II in C4 plant maize. No significant changes in the activity of PS II were observed in malate-treated C3 plant tobacco. It is suggested that the short term malate treatment will inhibit PS II of leaves which have C4 anatomy and C4 enzymes.
文摘Because the transient O3 injury of leaves is lost with time, the evaluation of O3 effect on the maximum quantum efficiency of PSII (Fv/Fm) is difficult. Thus, the authors examined Fv/Fm in rice leaves exposed to different O3 concentrations (0, 0.1, and 0.3 cm3·m-3, expressed as O0, O0.1, and O0.3) under different dark adaptation periods (0, 1, 5, 10, 20, and 30 min, expressed as D0, D1, D5, D10, D20, and D30) to ascertain its optimum time span. Fv/Fm was inhibited by O3;however in the O0 and O0.1 plants, it recovered during dark adaptation. In the O0.3 plants, Fv/Fm decreased gradually with time. F0 was found to be increased by O3, and it increased further in the O0.3 plants during dark adaptation. Under a high light intensity, Fm was decreased by O3, and the O3-induced damage to Fv/Fm was therefore more pronounced. However, the sensitivity of
文摘The deleterious effects of ultraviolet B(UV-B)radiation on photosynthesis and photosynthetic proteins of tropical and temperate plants have been studied.Like tropical plants(black gram and green gram),the temperate plants(carrot and radish)also successfully grown in the tropical region.They were exposed to enhanced UV-B radiation under field condition.Comparative studies show that under enhanced UV-B radiation photosynthetic activity was increased in black gram.In green gram and radish the UV-B radiation slightly enhanced the photosynthetic activity,but it inhibited the photosynthetic activity in carrot.The comparative results showed changes in contents of thylakoid 55,47,43,33,29,27-25,23 and 17 kDa polypeptides that were significantly lowered in UV-B treated carrot plant when compared to other plants.The PSII protein profile results showed a strong correlation between the presence of a membrane polypeptide and photosynthetic activity.In black gram and green gram the UV-B radiation did not produce any significant difference in the PSII polypeptides.As in the case of radish the UV-B radiation increased the accumulation of 33-28 kDa protein and affected expression of the 63 kDa protein.In the case of carrot,severe degradation of 32 kDa and 33 kDa,corresponding to D1 and D2 core proteins of PSII,was observed.It could be concluded that the ability of plants to tolerate increased levels of UV-B radiation,relative to photosynthetic capacity,depends on acclimation processes of the plant in the growing region.
基金supported by the National Natural Science Foundation of China (U2003214)the Western Youth Scholars Project of the Chinese Academy of Sciences (2021-XBQNXZ-006)。
文摘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.
基金supported by the Special Fund for Nonprofit Industry (Agriculture) Research Project (201303014)Earmarked Fund for Beijing Fruit Vegetable Innovation Team Project of Modern Agro-industry Technology Research System (GCTDZJ2014033007) in China
文摘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.
文摘The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated with spinach thylakoids, phycobiliproteins isolated from red and blue- green algae transferred light energy absorbed to spinach PSII. The efficiency of energy transfer was dependent on the kind of phycobiliproteins used. If spinach thylakoids were replaced by the thylakoids of Brassica chinensis, R phycoerythin or C- phycocyanin did not transfer their excitation energy to PSII of Brassica chinensis unless allophycocyanin was present.
基金Supported by the Shandong Provincial Natural Science Foundation(Nos.ZR2019MC015,ZR2020QC025,ZR2020MD092)the open project of Rongcheng Marine Industrial Technology Research Institute,Ludong University(No.KF20180001)the Key Technology Research and Development Program of Shandong(No.2019GSF107091)。
文摘To investigate the effect of reduced salinity on diatoms’ capacity to cope with changing ultraviolet radiation(U VR) and photosynthetically active radiation(PAR),Skeletonema costatum was grown in a range of salinity(15,25,and 35).The photo system Ⅱ(PSⅡ) function was analyzed by increasing PAR and UVR to mimic a mixing event in turbulent waters.The re sults show that high UVR exposure significantly reduced PSII activity,especially in cells grown at low salinity.UVR,but not salinity,stimulated the ’removal’ rate of PSII protein PsbA.Salinity alone,in the range of 15 to 35,did not regulate PSⅡ acceptor region;however,the low salinity+UVR treatment decreased the energy flux for electron transport per PSⅡ reaction center in S.costatum.It showed that low salinity exacerbated the damaging effect of UVR on PSⅡ function in S.costatum by suppressing Psb A protein synthe sis and modifying the photochemistry of PSⅡ.Although higher catalase(CAT) activity and NPQs were induced,they were unable to prevent the combined damage effect of low salinity+UVR.Our findings indicate that reduced salinity and increased UVR potentially affect the abundance and distribution of S.costatum with the escalation of climate disturbances.
文摘Nutrient enrichment experiments with nitrogen （N） and phosphorus （P） were conducted with samples from two stationsin the coastal waters of Qingdao, China, during summer to identify limiting nutrients. In late July of 2009, low P concentrations andthe maximum photochemical efficiency of photosystem II （Fv/Fm） in the initial samples together with Fv/Fm and chlorophyll a （Chl a）responses to P addition indicated P limitation at the two stations. In early August, low P levels still limited phytoplankton growth atstation A. Fv/Fm and Chl a were the highest in the NP treatments at station B, suggesting an N/P co-limitation. In mid-September,nutrient concentrations and Fv/Fm were elevated and phytoplankton communities were healthy. Greater Fv/Fm and Chl a in the treat-ments with added P than those without the addition suggested potential P limitation at station A. Lack of Fv/Fm and Chl a responsesfollowing nutrient additions indicated N and P repletion at station B. At the end of July 2010, neither N nor P was limited at station B.Additionally, Fv/Fm coupled with 24-h-long nutrient enrichment experiments can be used to detect P limitation and N/P co-limitationto natural populations. This method can be more accurate for assessing co-limitation than the use of criteria of nutrient concentrationsand ratios as indicators, and can provide more rapid results than nutrient addition bioassays using chlorophyll response as an indica-tor, when a population is potentially limited. Compared with the two conventional methods, the results based on F,/F~ can also pro-vide more detailed information about physiological states of the populations.
基金Supported by Youth Fund of Genetic Engineering of Provincial Finance(2018QNJJ-023)Applied Basic Research of Sichuan Science and Technology Program(2018JY0153)Excellent Thesis Fund Project of Genetic Engineering of Provincial Finance(2016 LWJJ-010)
文摘[Objective] The paper was to investigate effects of glyphosate stress on physiological characteristics and protein expression of photosystem Ⅱ(PSⅡ) in genentically modified soybean GTS 40-3-2 seedlings under severe drought condition. [Method] A pot experiment was carried out in growth chamber to determine the response of genetically modified soybean treated by severe drought stress and different concentrations of glyphosate at the third compound leaf stage. [Result] Severe drought treatment increased the electrolyte leakage(EL), superoxide dismutase(SOD) and peroxidase(POD) activities, and decreased the relative water content(RWC), chlorophyll content, and catalase(CAT) activity. The EL, SOD and POD activities were significantly increased in severe drought and glyphosate treatments, which were related to glyphosate concentrations. The chlorophyll content decreased, which was also related to glyphosate concentrations. But the BWC and CAT activity were not affected by glyphosate concentrations. Western blot displayed that PSⅡ protein Lhcb2 was not affected by stress conditions and stably expressed. D1, D2 and Lhcb4 protein level decreased, and there was no significant change in Lhcb1 expression under severe drought stress. The protein levels of D1, D2, Lhcb1 and Lhcb4 decreased with the increase of glyphosate concentrations under severe drought and glyphosate stress. When the glyphosate concentrations were 0.92 and 1.84 kg·ai/hm^2, the protein levels of D1, D2 and Lhcb4 were slightly higher than those in severe drought stress. When the glyphosate concentrations were 3.68 and 7.36 kg·ai/hm^2, the protein level of D1, D2, Lhcb1 and Lhcb4 decreased sharply. [Conclusion] This research provides a theoretical basis for production of genetically modified soybean.
基金support by the National Natural Science Foundation of China(32071959)the Natural Science Foundation of Shandong Province(ZR2020QC104)Taishan Industrial Leading Talents Project.
文摘With global warming, high-temperature(HT) stress has become a major abiotic stress for crops, in particular summer maize in China. Photosynthesis is sensitive to HT. Salicylic acid(SA) and 6-benzyladenine(6-BA) can improve the adaptation of plants to various biotic and abiotic stresses. However, their contribution to maintaining photosynthetic activity and alleviating photoinhibition in maize leaves under HT stress is still unclear. The effects of exogenous SA or 6-BA on growth, photosynthesis capacity, photosystem Ⅱ(PSII) activity, subcellular ultrastructure, antioxidant system, and plant hormones in maize leaves under HT stress were investigated. Under HT conditions, application of SA or 6-BA up-regulated gibberellin and zeatin content in leaves, increasing leaf area index(LAI). It also expanded the stomata by reducing abscisic acid and jasmonic acid content in leaves, cooling them and increasing CO2supply to photosynthesis. A higher net photosynthetic rate, combined with increased activity of the antioxidant system, alleviated oxidative stress in maize plants sprayed with SA or 6-BA, allowing them to maintain their chloroplast ultrastructure and PSII activity, in particular electron transfer from QAto QB. The increased LAI and net photosynthetic rate per unit leaf area also resulted in the accumulation of more biomass.
