To evaluate the potential of barley for the phytoremediation of soils contaminated by metals, we conducted a growth chamber experiment with plants exposed to various concentrations of Zn, Cd and Cr. Growth parameters,...To evaluate the potential of barley for the phytoremediation of soils contaminated by metals, we conducted a growth chamber experiment with plants exposed to various concentrations of Zn, Cd and Cr. Growth parameters, chlorophyll content and chlorophyll fluorescence were measured at 15 and 29 days after treatment application, and the metal concentration in the aerial part of the plant, the root and the soil was also measured. In all cases, the amount of metal accumulated in the plant increased by increasing the concentration of the applied metal, and the roots accumulated more metal than did the aerial part of the plant. The amount of Cr found in the soil was significantly lower than that of Cd and Zn. The toxic effect of Zn and Cd on the plant was low, affecting growth only at the highest concentrations. For Zn and Cd at the concentrations used, the decrease in water content was 14% compared with the control and 26% for Cr. For plants treated with the highest metal concentrations, the most significant differences were found in chlorophyll content, which had the lowest values compared with the control (23% for Zn, and 42% for Cd and Cr), and in chlorophyll fluorescence (2% for Zn, 23% for Cd and 29% for Cr). These decreases occurred 29 days after applying the Zn and Cd treatments. In plants treated with Cr, the decrease occurred 15 days after treatment application. Under our experimental conditions, barley is more tolerant to Zn and Cd than to Cr.展开更多
The potential role of exotic tree plantations in facilitating successional processes on degraded areas was evaluated in southern Ethiopia by comparing seedling characteristics, transpiration and photosynthetic perform...The potential role of exotic tree plantations in facilitating successional processes on degraded areas was evaluated in southern Ethiopia by comparing seedling characteristics, transpiration and photosynthetic performance of Podocarpus falcatus seedlings in Eucalyptus plantation, Pinus plantation, adjacent natural forest and clear-felled plantation site. P. falcatus seedlings exhibited differences in architecture between Eucalyptus and Pinus plantations. They had higher leaf area, shorter internode length and greater number of lateral branches in Eucalyptus plantation. At similar vapor pressure deficit (VPD), P. falcatus transpired much less than E. saligna, especially at higher VPDs. Analysis of fluorescence parameters in the leaves showed no significant differences in the level of dark-adapted and light-adapted fluorescence yield (Fv/Fm and ΔF/Fm′, respectively), electron transport rate (ETR) and nonphotochemical quenching (NPQ) among seedlings grown inside plantations and adjacent natural forest, indicating similar photosynthetic performance. Nevertheless, there was evidence of photoinhibition in P. falcatus in the clear-felled site which had low fluorescence yield but high values of NPQ as protection from photoamage. The light response curves of ETR, NPQ and ΔF/Fm′ showed similar light saturation behavior among the seedlings grown inside plantations and natural forest and suggested a sequence of light-adapted to shade-adapted behavior in Natural forest 〉 Eucalyptus plantation 〉 Pinus plantation. The results show the structural flexibility, better water-use and adaptability of P. falcatus in its use of the understory environment of plantation species.展开更多
In recent years,heavy metal hazards in the soil have seriously affected agricultural production.This study aims to examine the effects of different levels of heavy metal Zn on the growth,photosynthesis and physiologic...In recent years,heavy metal hazards in the soil have seriously affected agricultural production.This study aims to examine the effects of different levels of heavy metal Zn on the growth,photosynthesis and physiological characteristics of wheat,and provide a theoretical basis for the diagnosis and control of heavy metal pollution in agricultural production.The field test method was used to explore the changes of wheat agronomic traits,photosynthetic capacity,chlorophyll fluorescence parameters,spectral characteristic curve,active oxygen metabolism system,cell ultrastructure,and yield,under different Zn levels(0,250,500,750,and 1000 mg kg^(-1)).The results show that,low-level Zn treatments can effectively promote the synthesis of wheat chlorophyll,improve photosynthetic capacity,and increase yield.The yield of ZnL1(250 mg kg^(-1))was the highest in the two-year test,which increased by 20.4%in 2018 and 13.9%in 2019 compared with CK(0 mg kg^(-1)).However,a high Zn level had a significant stress effect on the photosystem of wheat.PIabs(reaction center performance index)and Fv/Fm(maximum photochemical efficiency)were significantly reduced,the active oxygen metabolism system was damaged,and the photosynthetic capacity was reduced,which in turn led to reduced yield.Among them,the yield of ZnL4(1000 mg kg^(-1))was the lowest in the two-year test,which was 28.1 and 16.4%lower than CK in 2018 and 2019,respectively.The green peak position of ZnL3 and ZnL4 had"red shift"to the long wave direction,while the red valley position of ZnL4 had"blue shift"to the short wave direction.Under ZnL4,some wheat leaf organelles began to decompose,vacuoles increased,cytoplasm decreased,cell walls thickened,chloroplast basal lamellae were disordered,and mitochondrial membranes disintegrated.Stepwise regression and Path analysis showed that Pn(net photosynthetic rate)played a leading role in the formation of yield.Redundancy(RDA)analysis showed that the optimal Zn level for wheat growth was about 250 mg kg^(-1),and wheat would be stressed when the soil Zn level exceeded 500 mg kg^(-1) in the test condition of this study.Findings of this study provide a theoretical basis for the diagnosis and prevention of heavy metal(Zn)pollution in the soil.展开更多
To investigate the effects of exogenous lanthanum (La) on Alternanthera philoxeroides (Mart.) Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution cultu...To investigate the effects of exogenous lanthanum (La) on Alternanthera philoxeroides (Mart.) Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution culture experiments under controlled condi- tions. Different concentrations of La (NO3)3 were used in our study. It was shown that 0. 1 and 0.5 mg/L La3+ alleviated the inhibition effect of perchlorate on A. philoxeroides, including relative growth yield, dry weight of different organs, leaf area and root activity. And La3+ prevented decline in the relative chlorophyll content and chlorophyll fluorescence parameters including Fv/Fm, Fv'/Frn', φPSll and ETR induced by perchlorate stress. Moreover, 0.5 mg/L La3+ showed an optimal mitigative effect, while excess La3+ (5.0 mg/L) led to synergistic effect on stress. Correlation analysis revealed a significant positive relationship between growth indexes and the chlorophyll fluorescence parameters, root activity and relative chlorophyll content (p〈0.05). The results suggested that appropriate concentration of La3+ could effectively alleviate growth inhibition and injury ofA. philoxeroides caused by perchlorate stress, and the mitigative effect of La3+ might be achieved by improving root activity, maintaining chlorophyll content and promoting photochemical efficiency of photosystem II ofA. philoxeroides under perchlorate stress.展开更多
To examine the synergetic effects of ocean acidification(OA)and light intensity on the photosynthetic performance of marine diatoms,the marine centric diatom Thalassiosira weissflogii was cultured under ambient low CO...To examine the synergetic effects of ocean acidification(OA)and light intensity on the photosynthetic performance of marine diatoms,the marine centric diatom Thalassiosira weissflogii was cultured under ambient low CO_(2)(LC,390μatm)and elevated high CO_(2)(HC,1000μatm)levels under low-light(LL,60μmol m^(-2)s^(-1))or high-light(HL,220μmol m^(-2)s^(-1))conditions for over 20 generations.HL stimulated the growth rate by 128 and 99%but decreased cell size by 9 and 7%under LC and HC conditions,respectively.However,HC did not change the growth rate under LL but decreased it by 9%under HL.LL combined with HC decreased both maximum quantum yield(FV/FM)and effective quantum yield(ΦPSII),measured under either low or high actinic light.When exposed to UV radiation(UVR),LL-grown cells were more prone to UVA exposure,with higher UVA and UVR inducing inhibition ofΦPSII compared with HL-grown cells.Light use efficiency(α)and maximum relative electron transport rate(rETRmax)were inhibited more in the HC-grown cells when UVR(UVA and UVB)was present,particularly under LL.Our results indicate that the growth light history influences the cell growth and photosynthetic responses to OA and UVR.展开更多
The effects of pristine polystyrene microplastics(pMPs)without any pretreatment at different concentrations(0,10,20,50,and 100 mg/L)on Phaeodactylum tricornutum Bohlin at two initial algae densities(105 and 106 cells/...The effects of pristine polystyrene microplastics(pMPs)without any pretreatment at different concentrations(0,10,20,50,and 100 mg/L)on Phaeodactylum tricornutum Bohlin at two initial algae densities(105 and 106 cells/mL)were assessed in this study.Hormesis-like effects were found when microalgae grew with pMPs.The results showed that pMPs inhibited microalgae growth under a high concentration of microplastics tolerated by individual algal cell(low initial algae density)(up to-80.189.71%)but promoted growth when the situation was opposite(up to 15.273.66%).The contents of photosynthetic pigments including chlorophyll a,chlorophyll c and carotenoids showed resistance to pMPs stress under a low initial algae density and increased with time,but the opposite was true under a high initial algae density.Compared with the low initial algae density group,Qp received less inhibition,and NPQ(heat dissipation)also decreased under the high initial algae density.Under the low initial algae density,OJIP parameters such as Sm,N,Area,Pi Abs,ѱo,φEo,TRo/RC and ETo/RC were more perturbed initially and returned to the levels of the control group(without pMPs)over time,but they remained stable throughout the experiment at high initial algae density.These results show that microplastics in the marine environment may have different toxic effects on P.tricornutum at different growth stages,which is of great significance for understanding the impact of microplastics on marine microalgae and aquatic ecosystems.展开更多
In order to analyze the adaptation potential of tomato shoots to a sudden increase in Cd concentration, tomato plants (Solanum lycopersicum L. var. Ailsa Craig) were exposed under controlled environmental conditions...In order to analyze the adaptation potential of tomato shoots to a sudden increase in Cd concentration, tomato plants (Solanum lycopersicum L. var. Ailsa Craig) were exposed under controlled environmental conditions to a high dose of this heavy metal (250 μm CdCl2) in nutrient solution for 7 and 14d. Both root and shoot growth was completely inhibited but all plants remained alive until the end of the treatment. Cell viability remained unaffected but the activity of the mitochondrial alternative pathway was stimulated by Cd stress at the expense of the cytochrome pathway. Cadmium concentration was higher in roots than in shoots and a decrease in the rate of net Cd translocation was noticed during the second week of stress. Cadmium decreased both leaf conductance (gl) and chlorophyll concentration. However, the effect on net CO2 assimilation remained limited and soluble sugars accumulated in leaves. Photochemical efficiency of PSII (FvlFm) was not affected despite a decrease in the number of reaction centers and an inhibition of electron transfer to acceptors of PSII. It is concluded that tomato shoot may sustain short term exposure to high doses of cadmium despite growth inhibition. This property implies several physiological strategies linked to both avoidance and tolerance mechanisms.展开更多
Aims Most plants are clonal in nature.Clonal ramets can share water,nutrients and photosynthate,especially when they experience patchy resources.Patch contrast(i.e.a difference in resources among patches)and patch dir...Aims Most plants are clonal in nature.Clonal ramets can share water,nutrients and photosynthate,especially when they experience patchy resources.Patch contrast(i.e.a difference in resources among patches)and patch direction(i.e.source–sink relations)are among the basic attributes of spatial patchiness.Here,I hypothesize that young established ramets in nutrient-rich patches support old ramets in nutrient-poor patches when ramets are subjected to different patch contrasts and patch directions.Methods In a greenhouse experiment,old and young ramets of Glechoma longituba were grown in four combinations consisting of patch contrast and patch direction.Minus patch direction refers to a patch combination in which parent ramets grow in nutrient-rich patches while connected daughter ramets grow in nutrient-poor ones and plus patch direction is the opposite direction.Imeasured photosynthesis and fluorescence traits,harvested all ramets,took morphological measures,weighed their dry mass and determined their nutrient uptake and use.Important Findings For parental ramets of G.longituba,patch contrast and patch direction and their interactions had no significant effects on net photosynthetic rate,maximal fluorescence yield,photochemical quenching(quenching refers to any process which decreases the fluorescence intensity of a given substance),non-photochemical quenching,nutrient uptake,biomass and stolon weight ratio.Patch direction alone significantly affected root weight ratio.Large patch contrast enhanced N use efficiency(NUE)and P use efficiency(PUE);plus patch direction decreased NUE,but increased PUE;the patch contrast by patch direction interaction affected PUE and K use efficiency(KUE).There were significant interactions between patch direction and patch contrast on PUE and KUE.It is concluded that soil nutrient patchiness may influence nutrient use strategies,but not nutrient uptake,photosynthesis and growth of parent ramets of G.longituba connected to daughter ramets,and that patch contrast and patch direction jointly affect PUE and KUE.展开更多
Objective:To study the oxidative stress and antioxidative response of Cinnamomum camphora seedlings exposed to nitrogen dioxide (NO2) fumigation.Methods:Measurements were made up of the growth,chlorophyll content,chlo...Objective:To study the oxidative stress and antioxidative response of Cinnamomum camphora seedlings exposed to nitrogen dioxide (NO2) fumigation.Methods:Measurements were made up of the growth,chlorophyll content,chlorophyll fluorescence,antioxidant system and lipid peroxidation of one-year-old C.camphora seedlings exposed to NO2 (0.1,0.5,and 4 μl/L) fumigation in open top chambers over a period of 60 d.Results:After the first 30 d,0.5 and 4.0 μl/L NO2 showed insignificant effects on the growth of C.camphora seedlings.However,exposure to 0.5 and 4.0 μl/L NO2 for 15 d significantly reduced their chlorophyll content (P<0.05),enhanced their malondialdehyde (MDA) content and superoxide dismutase (SOD) activity (P<0.05),and also significantly reduced the maximal quantum yield of PSII in the dark [the ratio of variable fluorescence to maximal fluorescence (Fv/Fm)] (P<0.05).In the latter 30 d,0.5 μl/L NO2 showed a positive effect on the vitality of the seedlings,which was reflected by a recovery in the ratio of Fv/Fm and chlorophyll content,and obviously enhanced growth,SOD activity,ascorbate (AsA) content and glutathione reductase (GR) activity (P<0.05);4.0 μl/L NO2 then showed a negative effect,indicated by significant reductions in chlorophyll content and the ratio of Fv/Fm,and inhibited growth (P<0.05).Conclusion:The results suggest adaptation of C.camphora seedlings to 60-d exposure to 0.1 and 0.5 μl/L NO2,but not to 60-d exposure to 4.0 μl/L NO2.C.camphora seedlings may protect themselves from injury by strengthening their antioxidant system in response to NO2-induced oxidative stress.展开更多
Dark septate endophytic(DSE) fungi are ubiquitous and cosmopolitan, and occur widely in association with plants in heavy metal stress environment. However, little is known about the effect of inoculation with DSE fung...Dark septate endophytic(DSE) fungi are ubiquitous and cosmopolitan, and occur widely in association with plants in heavy metal stress environment. However, little is known about the effect of inoculation with DSE fungi on the host plant under heavy metal stress.In this study, Gaeumannomyces cylindrosporus, which was isolated from Pb-Zn mine tailings in China and had been proven to have high Pb tolerance, was inoculated onto the roots of maize(Zea mays L.) seedlings to study the effect of DSE on plant growth, photosynthesis,and the translocation and accumulation of Pb in plant under stress of different Pb concentrations. The growth indicators(height, basal diameter, root length, and biomass) of maize were detected. Chlorophyll content, photosynthetic characteristics(net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO_2 concentration), and chlorophyll fluorescence parameters in leaves of the inoculated and non-inoculated maize were also determined. Inoculation with G. cylindrosporus significantly increased height,basal diameter, root length, and biomass of maize seedlings under Pb stress. Colonization of G. cylindrosporus improved the efficiency of photosynthesis and altered the translocation and accumulation of Pb in the plants. Although inoculation with G. cylindrosporus increased Pb accumulation in host plants in comparison to non-inoculated plants, the translocation factor of Pb in plant body was significantly decreased. The results indicated that Pb was accumulated mainly in the root system of maize and the phytotoxicity of Pb to the aerial part of the plant was alleviated. The improvement of efficiency of photosynthesis and the decrease of translocation factor of Pb, caused by DSE fungal colonization, were efficient strategies to improve Pb tolerance of host plants.展开更多
文摘To evaluate the potential of barley for the phytoremediation of soils contaminated by metals, we conducted a growth chamber experiment with plants exposed to various concentrations of Zn, Cd and Cr. Growth parameters, chlorophyll content and chlorophyll fluorescence were measured at 15 and 29 days after treatment application, and the metal concentration in the aerial part of the plant, the root and the soil was also measured. In all cases, the amount of metal accumulated in the plant increased by increasing the concentration of the applied metal, and the roots accumulated more metal than did the aerial part of the plant. The amount of Cr found in the soil was significantly lower than that of Cd and Zn. The toxic effect of Zn and Cd on the plant was low, affecting growth only at the highest concentrations. For Zn and Cd at the concentrations used, the decrease in water content was 14% compared with the control and 26% for Cr. For plants treated with the highest metal concentrations, the most significant differences were found in chlorophyll content, which had the lowest values compared with the control (23% for Zn, and 42% for Cd and Cr), and in chlorophyll fluorescence (2% for Zn, 23% for Cd and 29% for Cr). These decreases occurred 29 days after applying the Zn and Cd treatments. In plants treated with Cr, the decrease occurred 15 days after treatment application. Under our experimental conditions, barley is more tolerant to Zn and Cd than to Cr.
文摘The potential role of exotic tree plantations in facilitating successional processes on degraded areas was evaluated in southern Ethiopia by comparing seedling characteristics, transpiration and photosynthetic performance of Podocarpus falcatus seedlings in Eucalyptus plantation, Pinus plantation, adjacent natural forest and clear-felled plantation site. P. falcatus seedlings exhibited differences in architecture between Eucalyptus and Pinus plantations. They had higher leaf area, shorter internode length and greater number of lateral branches in Eucalyptus plantation. At similar vapor pressure deficit (VPD), P. falcatus transpired much less than E. saligna, especially at higher VPDs. Analysis of fluorescence parameters in the leaves showed no significant differences in the level of dark-adapted and light-adapted fluorescence yield (Fv/Fm and ΔF/Fm′, respectively), electron transport rate (ETR) and nonphotochemical quenching (NPQ) among seedlings grown inside plantations and adjacent natural forest, indicating similar photosynthetic performance. Nevertheless, there was evidence of photoinhibition in P. falcatus in the clear-felled site which had low fluorescence yield but high values of NPQ as protection from photoamage. The light response curves of ETR, NPQ and ΔF/Fm′ showed similar light saturation behavior among the seedlings grown inside plantations and natural forest and suggested a sequence of light-adapted to shade-adapted behavior in Natural forest 〉 Eucalyptus plantation 〉 Pinus plantation. The results show the structural flexibility, better water-use and adaptability of P. falcatus in its use of the understory environment of plantation species.
基金funded by the National Natural Science Foundation of China(41471279)the Key Research and Development Program in Shandong Province,China(2016CYJS05A1-7 and 2017CXGC0303)。
文摘In recent years,heavy metal hazards in the soil have seriously affected agricultural production.This study aims to examine the effects of different levels of heavy metal Zn on the growth,photosynthesis and physiological characteristics of wheat,and provide a theoretical basis for the diagnosis and control of heavy metal pollution in agricultural production.The field test method was used to explore the changes of wheat agronomic traits,photosynthetic capacity,chlorophyll fluorescence parameters,spectral characteristic curve,active oxygen metabolism system,cell ultrastructure,and yield,under different Zn levels(0,250,500,750,and 1000 mg kg^(-1)).The results show that,low-level Zn treatments can effectively promote the synthesis of wheat chlorophyll,improve photosynthetic capacity,and increase yield.The yield of ZnL1(250 mg kg^(-1))was the highest in the two-year test,which increased by 20.4%in 2018 and 13.9%in 2019 compared with CK(0 mg kg^(-1)).However,a high Zn level had a significant stress effect on the photosystem of wheat.PIabs(reaction center performance index)and Fv/Fm(maximum photochemical efficiency)were significantly reduced,the active oxygen metabolism system was damaged,and the photosynthetic capacity was reduced,which in turn led to reduced yield.Among them,the yield of ZnL4(1000 mg kg^(-1))was the lowest in the two-year test,which was 28.1 and 16.4%lower than CK in 2018 and 2019,respectively.The green peak position of ZnL3 and ZnL4 had"red shift"to the long wave direction,while the red valley position of ZnL4 had"blue shift"to the short wave direction.Under ZnL4,some wheat leaf organelles began to decompose,vacuoles increased,cytoplasm decreased,cell walls thickened,chloroplast basal lamellae were disordered,and mitochondrial membranes disintegrated.Stepwise regression and Path analysis showed that Pn(net photosynthetic rate)played a leading role in the formation of yield.Redundancy(RDA)analysis showed that the optimal Zn level for wheat growth was about 250 mg kg^(-1),and wheat would be stressed when the soil Zn level exceeded 500 mg kg^(-1) in the test condition of this study.Findings of this study provide a theoretical basis for the diagnosis and prevention of heavy metal(Zn)pollution in the soil.
基金Foundation item: Project supported by Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and National Basic Research Program of China (2006CB403301)
文摘To investigate the effects of exogenous lanthanum (La) on Alternanthera philoxeroides (Mart.) Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution culture experiments under controlled condi- tions. Different concentrations of La (NO3)3 were used in our study. It was shown that 0. 1 and 0.5 mg/L La3+ alleviated the inhibition effect of perchlorate on A. philoxeroides, including relative growth yield, dry weight of different organs, leaf area and root activity. And La3+ prevented decline in the relative chlorophyll content and chlorophyll fluorescence parameters including Fv/Fm, Fv'/Frn', φPSll and ETR induced by perchlorate stress. Moreover, 0.5 mg/L La3+ showed an optimal mitigative effect, while excess La3+ (5.0 mg/L) led to synergistic effect on stress. Correlation analysis revealed a significant positive relationship between growth indexes and the chlorophyll fluorescence parameters, root activity and relative chlorophyll content (p〈0.05). The results suggested that appropriate concentration of La3+ could effectively alleviate growth inhibition and injury ofA. philoxeroides caused by perchlorate stress, and the mitigative effect of La3+ might be achieved by improving root activity, maintaining chlorophyll content and promoting photochemical efficiency of photosystem II ofA. philoxeroides under perchlorate stress.
基金This study was supported by the National Natural Science Foundation of China(41720104005,41721005,41890803)Key Research and Development Program of Anhui Province(202004i07020004)+3 种基金Excellent Youth Scholars Support Program of Anhui Province(gxyq2021212)MEL Visiting Fellowship Program(MELRS2008)Research Platform of Eco-Environmental Protection Research Centre of Xin’an River Basin,Huangshan University(kypt202102)The authors are grateful to the laboratory engineers Xianglan Zeng and Wenyan Zhao for their logistical and technical support.
文摘To examine the synergetic effects of ocean acidification(OA)and light intensity on the photosynthetic performance of marine diatoms,the marine centric diatom Thalassiosira weissflogii was cultured under ambient low CO_(2)(LC,390μatm)and elevated high CO_(2)(HC,1000μatm)levels under low-light(LL,60μmol m^(-2)s^(-1))or high-light(HL,220μmol m^(-2)s^(-1))conditions for over 20 generations.HL stimulated the growth rate by 128 and 99%but decreased cell size by 9 and 7%under LC and HC conditions,respectively.However,HC did not change the growth rate under LL but decreased it by 9%under HL.LL combined with HC decreased both maximum quantum yield(FV/FM)and effective quantum yield(ΦPSII),measured under either low or high actinic light.When exposed to UV radiation(UVR),LL-grown cells were more prone to UVA exposure,with higher UVA and UVR inducing inhibition ofΦPSII compared with HL-grown cells.Light use efficiency(α)and maximum relative electron transport rate(rETRmax)were inhibited more in the HC-grown cells when UVR(UVA and UVB)was present,particularly under LL.Our results indicate that the growth light history influences the cell growth and photosynthetic responses to OA and UVR.
基金This study was supported by the National Natural Science Foundation of China(No.52071030)Science and Technology Program of Henan Province(No.132102310498).
文摘The effects of pristine polystyrene microplastics(pMPs)without any pretreatment at different concentrations(0,10,20,50,and 100 mg/L)on Phaeodactylum tricornutum Bohlin at two initial algae densities(105 and 106 cells/mL)were assessed in this study.Hormesis-like effects were found when microalgae grew with pMPs.The results showed that pMPs inhibited microalgae growth under a high concentration of microplastics tolerated by individual algal cell(low initial algae density)(up to-80.189.71%)but promoted growth when the situation was opposite(up to 15.273.66%).The contents of photosynthetic pigments including chlorophyll a,chlorophyll c and carotenoids showed resistance to pMPs stress under a low initial algae density and increased with time,but the opposite was true under a high initial algae density.Compared with the low initial algae density group,Qp received less inhibition,and NPQ(heat dissipation)also decreased under the high initial algae density.Under the low initial algae density,OJIP parameters such as Sm,N,Area,Pi Abs,ѱo,φEo,TRo/RC and ETo/RC were more perturbed initially and returned to the levels of the control group(without pMPs)over time,but they remained stable throughout the experiment at high initial algae density.These results show that microplastics in the marine environment may have different toxic effects on P.tricornutum at different growth stages,which is of great significance for understanding the impact of microplastics on marine microalgae and aquatic ecosystems.
基金the Fonds pour la Recherche dans l’Industrie et l’Agriculture(FRIA)the Fond Spcial pour la Recherche (FSR) from the CatholicUniversity of Louvain.
文摘In order to analyze the adaptation potential of tomato shoots to a sudden increase in Cd concentration, tomato plants (Solanum lycopersicum L. var. Ailsa Craig) were exposed under controlled environmental conditions to a high dose of this heavy metal (250 μm CdCl2) in nutrient solution for 7 and 14d. Both root and shoot growth was completely inhibited but all plants remained alive until the end of the treatment. Cell viability remained unaffected but the activity of the mitochondrial alternative pathway was stimulated by Cd stress at the expense of the cytochrome pathway. Cadmium concentration was higher in roots than in shoots and a decrease in the rate of net Cd translocation was noticed during the second week of stress. Cadmium decreased both leaf conductance (gl) and chlorophyll concentration. However, the effect on net CO2 assimilation remained limited and soluble sugars accumulated in leaves. Photochemical efficiency of PSII (FvlFm) was not affected despite a decrease in the number of reaction centers and an inhibition of electron transfer to acceptors of PSII. It is concluded that tomato shoot may sustain short term exposure to high doses of cadmium despite growth inhibition. This property implies several physiological strategies linked to both avoidance and tolerance mechanisms.
基金National Natural Science Foundation of China(40435014).
文摘Aims Most plants are clonal in nature.Clonal ramets can share water,nutrients and photosynthate,especially when they experience patchy resources.Patch contrast(i.e.a difference in resources among patches)and patch direction(i.e.source–sink relations)are among the basic attributes of spatial patchiness.Here,I hypothesize that young established ramets in nutrient-rich patches support old ramets in nutrient-poor patches when ramets are subjected to different patch contrasts and patch directions.Methods In a greenhouse experiment,old and young ramets of Glechoma longituba were grown in four combinations consisting of patch contrast and patch direction.Minus patch direction refers to a patch combination in which parent ramets grow in nutrient-rich patches while connected daughter ramets grow in nutrient-poor ones and plus patch direction is the opposite direction.Imeasured photosynthesis and fluorescence traits,harvested all ramets,took morphological measures,weighed their dry mass and determined their nutrient uptake and use.Important Findings For parental ramets of G.longituba,patch contrast and patch direction and their interactions had no significant effects on net photosynthetic rate,maximal fluorescence yield,photochemical quenching(quenching refers to any process which decreases the fluorescence intensity of a given substance),non-photochemical quenching,nutrient uptake,biomass and stolon weight ratio.Patch direction alone significantly affected root weight ratio.Large patch contrast enhanced N use efficiency(NUE)and P use efficiency(PUE);plus patch direction decreased NUE,but increased PUE;the patch contrast by patch direction interaction affected PUE and K use efficiency(KUE).There were significant interactions between patch direction and patch contrast on PUE and KUE.It is concluded that soil nutrient patchiness may influence nutrient use strategies,but not nutrient uptake,photosynthesis and growth of parent ramets of G.longituba connected to daughter ramets,and that patch contrast and patch direction jointly affect PUE and KUE.
基金Project supported by Zhejiang Keystone Projects (No.2005C22056)the Zhejiang Provincial Natural Science Foundation of China (No.Y5080011)
文摘Objective:To study the oxidative stress and antioxidative response of Cinnamomum camphora seedlings exposed to nitrogen dioxide (NO2) fumigation.Methods:Measurements were made up of the growth,chlorophyll content,chlorophyll fluorescence,antioxidant system and lipid peroxidation of one-year-old C.camphora seedlings exposed to NO2 (0.1,0.5,and 4 μl/L) fumigation in open top chambers over a period of 60 d.Results:After the first 30 d,0.5 and 4.0 μl/L NO2 showed insignificant effects on the growth of C.camphora seedlings.However,exposure to 0.5 and 4.0 μl/L NO2 for 15 d significantly reduced their chlorophyll content (P<0.05),enhanced their malondialdehyde (MDA) content and superoxide dismutase (SOD) activity (P<0.05),and also significantly reduced the maximal quantum yield of PSII in the dark [the ratio of variable fluorescence to maximal fluorescence (Fv/Fm)] (P<0.05).In the latter 30 d,0.5 μl/L NO2 showed a positive effect on the vitality of the seedlings,which was reflected by a recovery in the ratio of Fv/Fm and chlorophyll content,and obviously enhanced growth,SOD activity,ascorbate (AsA) content and glutathione reductase (GR) activity (P<0.05);4.0 μl/L NO2 then showed a negative effect,indicated by significant reductions in chlorophyll content and the ratio of Fv/Fm,and inhibited growth (P<0.05).Conclusion:The results suggest adaptation of C.camphora seedlings to 60-d exposure to 0.1 and 0.5 μl/L NO2,but not to 60-d exposure to 4.0 μl/L NO2.C.camphora seedlings may protect themselves from injury by strengthening their antioxidant system in response to NO2-induced oxidative stress.
基金supported by the National Natural Science Foundation of China (Nos. 41671268, 31270639, and 31400435)the Program for Changjiang Scholars and Innovative Research Team in University of China (No. IRT1035)+1 种基金the Hubei Provincial Natural Science Foundation of China (No. 2015CFB596)the Shaanxi Provincial Science and Technology Innovation Project Plan of China (No. 2016KTCL02-07)
文摘Dark septate endophytic(DSE) fungi are ubiquitous and cosmopolitan, and occur widely in association with plants in heavy metal stress environment. However, little is known about the effect of inoculation with DSE fungi on the host plant under heavy metal stress.In this study, Gaeumannomyces cylindrosporus, which was isolated from Pb-Zn mine tailings in China and had been proven to have high Pb tolerance, was inoculated onto the roots of maize(Zea mays L.) seedlings to study the effect of DSE on plant growth, photosynthesis,and the translocation and accumulation of Pb in plant under stress of different Pb concentrations. The growth indicators(height, basal diameter, root length, and biomass) of maize were detected. Chlorophyll content, photosynthetic characteristics(net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO_2 concentration), and chlorophyll fluorescence parameters in leaves of the inoculated and non-inoculated maize were also determined. Inoculation with G. cylindrosporus significantly increased height,basal diameter, root length, and biomass of maize seedlings under Pb stress. Colonization of G. cylindrosporus improved the efficiency of photosynthesis and altered the translocation and accumulation of Pb in the plants. Although inoculation with G. cylindrosporus increased Pb accumulation in host plants in comparison to non-inoculated plants, the translocation factor of Pb in plant body was significantly decreased. The results indicated that Pb was accumulated mainly in the root system of maize and the phytotoxicity of Pb to the aerial part of the plant was alleviated. The improvement of efficiency of photosynthesis and the decrease of translocation factor of Pb, caused by DSE fungal colonization, were efficient strategies to improve Pb tolerance of host plants.