Physiological indices related to the efficiency (F-v/F-m) of light energy conversion in PS II and the peroxidation of membrane lipid were measured in leaves of Oryza sativa L. sp. indica rice cv. 'Shanyou 63' ...Physiological indices related to the efficiency (F-v/F-m) of light energy conversion in PS II and the peroxidation of membrane lipid were measured in leaves of Oryza sativa L. sp. indica rice cv. 'Shanyou 63' and sp. japonica rice cv. '9516'' under different temperatures and fight intensities for 4 days. No changes in F-v/F-m and membrane lipid peroxidation product (MDA) were observed, so neither photoinhibition nor photooxidation happened in both rice cultivars under moderate temperature and medium light intensity. However, F-v/F-m dropped obviously with no change in MDA contents, and photoinhibition appeared in indica rice cv. 'Shanyou 63' under medium temperature and strong light intensity. Furthermore, both photoinhibition and photooxidation were observed in two rice cultivars under chilling temperature and strong light intensity. Experiments with inhibitors under chilling temperature and strong light intensity showed that indica rice had a decrease in DI protein content and SOD activity, and the extent of inhibition of xanthophyll. cycle and nonphotochemical quenching (qN) was larger, and a higher level of MDA was observed. The photoinhibition and photooxidation in indica rice were more distinct as compared with japonica rice. The authors suggested that PS II light energy conversion efficiency (F-v/F-m) and membrane lipid peroxidation were the key indices for the detection of photooxidation.展开更多
Relationships between fluorescence parameters and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa L.) during later growth stage were studied under chilling temperature and strong light ...Relationships between fluorescence parameters and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa L.) during later growth stage were studied under chilling temperature and strong light stress conditions. Results showed that D1 protein contents of PSⅡ in photosynthetic apparatus dropped, the generation of antheraxanthin (A) and zeaxanthin (Z) of xanthophyll cycle were inhibited partly, PSⅡ photochemical efficiency (F v/F m)and non-photochemical quenching (q N) were also decreased obviously. In addition, endogenous active oxygen scavenger—superoxide dismutase (SOD) reduced, superoxide anion radical (O -· 2) and malondialdehyde (MDA) accumulated, as a result, photooxidation of leaves occurred under chilling temperature and strong light stress conditions. Obvious differences in the changes of the above mentioned physiological parameters between indica and japonica rice were observed. Experiments in leaves treated with inhibitors under chilling temperature and strong light conditions showed that indica rice was more sensitive to chilling temperature with strong light and subjected to photooxidation more than japonica rice. Notable positive correlation between D1 protein contents and F v/F m or (A+Z)/(A+Z+V), and a marked negative correlation between F v/F m and MDA contents were obtained by regression analysis in indica and japonica rice during chilling temperature and strong light conditions. According to the facts mentioned above, it was inferred that PSⅡ photochemical efficiency(F v/F m) was the key index to forecast for the prediction of photooxidation under stress circumstances and the physiological basis were the synthetic capacity of D1 protein and the protection of xanthophyll cycle.展开更多
The purpose of the present studies was analysis of the age induced changes in photochemical efficiency and xanthophyils cycle pigments of the primary cabbage （Brassica oleracea L. cv. Capitata f. alba） leaves. Photo...The purpose of the present studies was analysis of the age induced changes in photochemical efficiency and xanthophyils cycle pigments of the primary cabbage （Brassica oleracea L. cv. Capitata f. alba） leaves. Photochemical efficiency of photosystem Ⅱ （PS Ⅱ） was studied by a pulse amplitude modulated chlorophyll fluorescence apparatus, chlorophyll concentration was analysis spectrophotometrically and xanthophyll cycle pigments were estimated by high-pressure liquid chromatography （HPLC）. Leaf senescence was accompanied with a decrease both in chlorophylls concentration, the photochemical efficiency and rate constant for PS Ⅱ photochemistry whereas non-photochemical parameters increased. Excitation pressure （1-qP） which is a measure of relative lumen acidification increased by 1.2x in aging leaves. The maximum quantum yield of PS Ⅱ showed no significant change. The level of de-epoxidised xanthophylls increased but the concentration of mono- and di-epoxy xanthophylls decreased in aging leaves. A linear relationship between the excitation pressure and the depoxidation state of the xanthophyll cycle pigments and lutein, during the onset of senescence suggests that excitation pressure can be used as a sensor for monitoring the onset of senescence as well for the de-epoxidation state of the xanthophylls responsible for non-photochemical quenching in stressed leaves.展开更多
Biogeochemical cycling of mercury in the young Three Gorges Reservoir （TGR）, China, is strongly considered. Although methylmercury （MMHg） photodegradation （PD） is an important process involved in mercury cycling...Biogeochemical cycling of mercury in the young Three Gorges Reservoir （TGR）, China, is strongly considered. Although methylmercury （MMHg） photodegradation （PD） is an important process involved in mercury cycling in this zone, little is known about this process. In situ incubation experiments were therefore performed to quantify the effect of different wave- length radiations and environmental factors on the PD process of MMHg in the water bodies of TGR. It was found that the ef- fect of solar radiation on MMHg PD was highly dependent on wavelength and water depth. All PD-rate constants resulting from each wavelength range decreased rapidly with water depth. For surface water, UV-A radiation （320-400 nm） was the key driver, accounting for 49%-62% of MMHg PD. For the entire water column, both photosynthetically active radiation （PAR, 400-700 nm） and UV-A were responsible for MMHg PD. MMHg PD fluxes peaked in summer （7.5-18 ng m-2 d-1）, followed by spring （3.3-8.0 ng m-2 d-1）, autumn （1.0-2.7 ng m-2 d-1）, and winter （0.060-0.15 ng m-2 d-1）. The annual fluxes of MMHg PD were estimated to be 1.1-2.8 μg m-2 at. Filtering the reservoir water and amending it with chemicals （i.e., CV, NO C, and dissolved organic matter （DOM）） showed significant effects on MMHg PD rate constants. Stepwise regression analysis showed that intensity of solar radiation, suspended particulate matter （SPM）, DOM, CI-, and NO3- were involved in the PD process. Path analysis clarified the relationship between MMHg PD rate constants and environmental variables, as well as the comparative strength of direct and indirect relationships among variables. The results are of great importance for understanding MMHg cycling characteristics in TGR and also facilitate the understanding of the underlying process, MMHg PD, in natural waters.展开更多
文摘Physiological indices related to the efficiency (F-v/F-m) of light energy conversion in PS II and the peroxidation of membrane lipid were measured in leaves of Oryza sativa L. sp. indica rice cv. 'Shanyou 63' and sp. japonica rice cv. '9516'' under different temperatures and fight intensities for 4 days. No changes in F-v/F-m and membrane lipid peroxidation product (MDA) were observed, so neither photoinhibition nor photooxidation happened in both rice cultivars under moderate temperature and medium light intensity. However, F-v/F-m dropped obviously with no change in MDA contents, and photoinhibition appeared in indica rice cv. 'Shanyou 63' under medium temperature and strong light intensity. Furthermore, both photoinhibition and photooxidation were observed in two rice cultivars under chilling temperature and strong light intensity. Experiments with inhibitors under chilling temperature and strong light intensity showed that indica rice had a decrease in DI protein content and SOD activity, and the extent of inhibition of xanthophyll. cycle and nonphotochemical quenching (qN) was larger, and a higher level of MDA was observed. The photoinhibition and photooxidation in indica rice were more distinct as compared with japonica rice. The authors suggested that PS II light energy conversion efficiency (F-v/F-m) and membrane lipid peroxidation were the key indices for the detection of photooxidation.
文摘Relationships between fluorescence parameters and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa L.) during later growth stage were studied under chilling temperature and strong light stress conditions. Results showed that D1 protein contents of PSⅡ in photosynthetic apparatus dropped, the generation of antheraxanthin (A) and zeaxanthin (Z) of xanthophyll cycle were inhibited partly, PSⅡ photochemical efficiency (F v/F m)and non-photochemical quenching (q N) were also decreased obviously. In addition, endogenous active oxygen scavenger—superoxide dismutase (SOD) reduced, superoxide anion radical (O -· 2) and malondialdehyde (MDA) accumulated, as a result, photooxidation of leaves occurred under chilling temperature and strong light stress conditions. Obvious differences in the changes of the above mentioned physiological parameters between indica and japonica rice were observed. Experiments in leaves treated with inhibitors under chilling temperature and strong light conditions showed that indica rice was more sensitive to chilling temperature with strong light and subjected to photooxidation more than japonica rice. Notable positive correlation between D1 protein contents and F v/F m or (A+Z)/(A+Z+V), and a marked negative correlation between F v/F m and MDA contents were obtained by regression analysis in indica and japonica rice during chilling temperature and strong light conditions. According to the facts mentioned above, it was inferred that PSⅡ photochemical efficiency(F v/F m) was the key index to forecast for the prediction of photooxidation under stress circumstances and the physiological basis were the synthetic capacity of D1 protein and the protection of xanthophyll cycle.
文摘The purpose of the present studies was analysis of the age induced changes in photochemical efficiency and xanthophyils cycle pigments of the primary cabbage （Brassica oleracea L. cv. Capitata f. alba） leaves. Photochemical efficiency of photosystem Ⅱ （PS Ⅱ） was studied by a pulse amplitude modulated chlorophyll fluorescence apparatus, chlorophyll concentration was analysis spectrophotometrically and xanthophyll cycle pigments were estimated by high-pressure liquid chromatography （HPLC）. Leaf senescence was accompanied with a decrease both in chlorophylls concentration, the photochemical efficiency and rate constant for PS Ⅱ photochemistry whereas non-photochemical parameters increased. Excitation pressure （1-qP） which is a measure of relative lumen acidification increased by 1.2x in aging leaves. The maximum quantum yield of PS Ⅱ showed no significant change. The level of de-epoxidised xanthophylls increased but the concentration of mono- and di-epoxy xanthophylls decreased in aging leaves. A linear relationship between the excitation pressure and the depoxidation state of the xanthophyll cycle pigments and lutein, during the onset of senescence suggests that excitation pressure can be used as a sensor for monitoring the onset of senescence as well for the de-epoxidation state of the xanthophylls responsible for non-photochemical quenching in stressed leaves.
基金financially supported by the National Basic Research Program of China(2013CB430004)the National Natural Science Foundation of China(41373113 and 41173116)
文摘Biogeochemical cycling of mercury in the young Three Gorges Reservoir （TGR）, China, is strongly considered. Although methylmercury （MMHg） photodegradation （PD） is an important process involved in mercury cycling in this zone, little is known about this process. In situ incubation experiments were therefore performed to quantify the effect of different wave- length radiations and environmental factors on the PD process of MMHg in the water bodies of TGR. It was found that the ef- fect of solar radiation on MMHg PD was highly dependent on wavelength and water depth. All PD-rate constants resulting from each wavelength range decreased rapidly with water depth. For surface water, UV-A radiation （320-400 nm） was the key driver, accounting for 49%-62% of MMHg PD. For the entire water column, both photosynthetically active radiation （PAR, 400-700 nm） and UV-A were responsible for MMHg PD. MMHg PD fluxes peaked in summer （7.5-18 ng m-2 d-1）, followed by spring （3.3-8.0 ng m-2 d-1）, autumn （1.0-2.7 ng m-2 d-1）, and winter （0.060-0.15 ng m-2 d-1）. The annual fluxes of MMHg PD were estimated to be 1.1-2.8 μg m-2 at. Filtering the reservoir water and amending it with chemicals （i.e., CV, NO C, and dissolved organic matter （DOM）） showed significant effects on MMHg PD rate constants. Stepwise regression analysis showed that intensity of solar radiation, suspended particulate matter （SPM）, DOM, CI-, and NO3- were involved in the PD process. Path analysis clarified the relationship between MMHg PD rate constants and environmental variables, as well as the comparative strength of direct and indirect relationships among variables. The results are of great importance for understanding MMHg cycling characteristics in TGR and also facilitate the understanding of the underlying process, MMHg PD, in natural waters.
