992 resultados para chlorophyll fluorescence
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200.6 1.4-5.8 ITEX-----OTC 1OTC OTC0.280.461.4OTCOTC 2 OTC OTC 3 OTC10OTC10OTC 4 OTC(10)0-30cmOTC0-10cm20-30cm 5 OTCOTCOTC 6 LMRRMRR/SSMRRMRR/SSMRLMR 7 abab 3AEgsPmaxRdayAQYLSPLCPAEgsPmaxRdayAQYLSPLCP Fv/FmYieldqPFv/FmYieldqPqN 8 Enrichment of atmospheric greenhouse gases resulted from human activities such as fossil fuel burning and deforestation has increased global mean temperature by 0.6 in the 20th century and is predicted to increase in this century by 1.4-5.8 . The global warming will have profound, long-term impacts on terrestrial plants and ecosystems. The ecoologcial consequences arising from global warming have also become the very important issuses of global change research. The terrestrial habitats of high-elevation and high-latitude ecosystems are regarded as the most sensitive to changing climate. The alpine meadow ecosystme, which resulted from the composite effects of mountain extreme climatic factors in Tibetan Plateau, is thus thought to be especially vulnerable and sensitive to global warming. In this paper, the response of plant community and several main species in the alpine meadow of Northewst Sichuan to experimemtal warming was studied by using open-top chambers (OTC). The aim of the this study was to research the warming effects on plant community structure, substance allocation, growth and physiological processes of several mian species, and to explore the biological and ecological mechanism of how the alpine meadow plants acclimate and adapt to future global warming. The results were as follows: 1. Warming effects of OTC The mean soil temperature, soil surface temperature and air temperature in OTC manipulation increased by 0.280.46 and 1.4 compared to the control during the growing season. This suggested that the OTC used in our study had increased temperature there. Meanwhile, the OTC manipulation slightly altered thermal conditions, but the same amount of precipitation was supplied to both the OTC manipulation and the control, so higher soil evaporation and plant transpiration in OTC manipulation directly lead to the decrease of soil surface water content. 2. The reponse of community structure to experimental warming The species richness was not changed by the short-term effect of OTC manipulation. However, experimental warming changed the microenvironment of plant community, therefore competitive balances among species were shift, leading to changes in species dominance. In the present study, the dominant plant species in the control plots were some forbs including Potentilla anserine, Geranium pylzowianum, Thlaspi arvense and Arenaria serpyllifolia, however, the importance value of some gramineous grasses including Elymus nutans, Deschampsia caespitosa, Festuca ovina, and some forbs including Euphrasia tatarica and Rumex acetosa significantly increased in OTC. The different biology characteristics and resource utilizations between gramineous grasses and forbs, and enhanced temperature caused change in some environment factors such as soil water content. As a result, the coverage and biomass of gramineous grasses significantly increased in OTC compared to the control, however, the coverage and biomass of forbs singnifciantly decreased in OTC compared to the control. 3. The reponse of plant growing season to experimental warming Both the standing dead and fallen litter biomass in OTC were lower than those in the control in October, and the biomass of aboveground live-vegetation in OTC was higher than that of the control. The results indicated that the senescence of plants was postponed, and the growing season was prolonged in our research. 4. The reponse of community biomass accumulation and its allocation to experimental warming Experimental warming caused the decrease of aboveground live biomass and belowground root biomass except for the aboveground live biomass in October. Experimental warming also had pronounced effects on the pattern of root biomass allocation. In the present study, the root biomass in 0-10cm soil layer increased in OTC manipulation compared to the control, however, the root biomass in the 20-30cm soil layer decreased in OTC manipulation compared to the control. 5. The reponse of community C and N content to experimental warming The C concentration and stock in aboveground live and belowground root both increased in OTC manipulation compared to the control. However, the N concentration and stock in aboveground live and belowground root both decreased in OTC manipulation compared to the control. 6. The reponse of gowth and biomass, C and N alloction of several species to experimental warming Experimental warming significantly increased the height, SLA (specific leaf area) and aboveground biomass of Elymus nutans in OTC manipulation compared to the control. The SLA and total biomass of Rumex acetosa also significantly increased in OTC manipulation compared to control, among the different components of Rumex acetosa, leaf biomass significantly increased, but root biomass significantly decreased in OTC manipulation compared to the control. However, the height, SLA and total biomass of Potentilla anserina significantly decreased in OTC manipulation compared to the control, among the different component of Potentilla anserina, leaf and stem biomass significantly decreased, but root biomass significantly increased in OTC manipulation compared to the control. The LMR (leaf mass ratio), RMR (root mass ratio), R/S (shoot/root biomass ration) and root C concentration of Rumex acetosa significantly increased in OTC manipulation compared to outside control, also, Rumex acetosa allocated relatively more C and N content to leaf and root in response to experimental warming, however, the SMR (stem mass ration) and root N concentration of Rumex acetosa significantly decreased in OTC manipulation compared to outside control, also, Rumex acetosa allocated relatively less C and N content to stem in response to experimental warming. The RMR and R/S of Potentilla anserina significantly increased in OTC manipulation compared to outside control, also, Potentilla anserina allocated relatively more C and N content to root in response to experimental warming, however, the SMR and LMR of Potentilla anserina significantly decreased in OTC manipulation compared to outside control, also, Potentilla anserina allocated relatively less C and N content to leaf in response to experimental warming. 7. The reponse of physiological processes of several species to experimental warming Experimental warming significantly increased chlorophyll a, chlorophyll b and total chlorophyll of Elymus nutans and Rumex acetosa in OTC manipulation compared to outside control. However, chlorophyll a, chlorophyll b, total chlorophyll and carotenoid of Potentilla anserina in OTC manipulation significantly decreased compared to outside control. Experimental warming had pronounced effects on gas exchange of Elymus nutans, Rumex acetosa and Potentilla anserine. In the present study, warming markedly increased the light response curves of Elymus nutans and Rumex acetosa in OTC manipulation compared to outside control, and also singnificantly increased A (net photosynthesis rate), E (transpiration rate), gs (stomatal conductance), Pmax (maximum net photosynthetic rate), Rday (dark respiration rate), AQY (apparent quantum yield) and LSP (light saturation point), but LCP (photosynthetic light compensation) of Elymus nutans and Rumex acetosa in OTC manipulation singnificantly decreased compared to outside control. However, warming markedly decreased the light response curves of Potentilla anserina in OTC manipulation compared to outside control, and also singnificantly decreased A, E, gs, Pmax, Rday, AQY and LSP, but LCP of Potentilla anserina in OTC manipulation singnificantly increased compared to outside control. Experimental warming singnificantly increased the chlorophyll fluorescence kinetics parameters such as Fv/Fm, Yield and qP of Elymus nutans and Rumex acetosa and qN of Potentilla anserina in OTC manipulation, but Fv/Fm, Yield and qP of Potentilla anserina in OTC manipulation singnificantly decreased. 8. The reponse of antioxidative systems of several species to experimental warming Experimental warming tended to increase the activities of antioxidative enzymes and stimulate the role of non-enzymes of Elymus nutans and Rumex acetosa. As a result, MDA content of Elymus nutans and Rumex acetosa decreased. The activities of antioxidative enzymes and non-enzymes of Potentilla anserina also significantly increased in OTC manipulation, but more O2- was produced because of lower soil water content, and the O2- accumulation exceeded the defense ability of antioxidative systems and non-enzymes fuctions. As a result, MDA content of Potentilla anserine still increased in OTC manipulation compared to outside control.
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Sophora davidiiBauhinia faberi var. microphyllaCampylotropics polyantha4-5WUE 1) 2) WUE WUWUEWUE 3) 12P/S 4) RWCPngsRWCTlTrPn-PSFv/FmYieldqPNPQPn40% FC 5) 20% FCIII80% FC Drought is often a key factor limiting plant establishment, growth and distribution inmany regions of the world. The harsh environmental conditions and long-termanthropogenic disturbance had resulted in habitat destruction in the dry valley ofMinjiang river, southwest China. Recently, it tended to be more severe on the vegetationdegradation, soil erosion and water loss, natural disaster, as well as desertification, whichimpact on regional booming economy and harmonious development, and would be verydangerous to the environmental security in the middle and lower reaches of Yangzi River.Therefore, ecological restoration in the dry valley is one of the vital tasks in China. Waterdeficit is known to affect adversely vegetation restoration in this place. Moreover, in thecontext of climate change, an increased frequency of drought stress might occur at aregional scale in the dry valleys of Minjiang River. The selection of appropriate plantingspecies for vegetation restoration in regard to regional conditions is an important issue atpresent and in further. The research on responses of indigenous species to drought stresscould provide insights into the improvement of the vegetation restoration in the dry valleys of Minjiang River. In this paper, the responses of three indigenous leguminous shrubs, Sophora davidii,Bauhinia faberi var. microphylla and Campylotropics polyantha, to various soil watersupplies were studied in order to assess drought tolerance of seedlings, and to compare interspecific differences in seedlings responses to drought stress. The results were as follows: 1 Growth and reproduction of shrubs in response to drought stress Seedling growth reduced significantly while leaf senescence accelerated underdrought stress, the cumulative responses to prolonged drought were found. The capacityfor reproduction was limited by severe drought stress, and improved by moderate droughtstress. Leaf responses were more sensitive than shoot to various water supplies. 2 WUE, biomass production and its partitioning of shrubs in response to drought stress Drought stress reduced significantly the total dry mass and their components ofseedlings, and altered more biomass allocation to root system, showing higher R/S ratiounder drought. Water use (WU) and water-use efficiency (WUE) of both S. davidii and B.faberi var. microphylla declined strongly with drought stress. The WU C. polyantha ofalso declined with drought stress, but WUE improved under moderate drought stress. 3 Anatomical characteristics and ultrastructures of leaves in response to drought stress There were xeromorphic for S. davidii leaves and mesomorphic for B. faberi var.microphylla and C. polyantha at the all water supplies. The foundational changes in leafstructures were not found with drought stress. However, mesophyll thickness, the areas ofstomatal and epidermis reduced slightly while the densities of stomatal and epidermisincreased under severe drought stress. Variations in these parameters could mainly be duoto cell size. Other structures did not displayed significant changes with drought stress. 4 Physiological responses of shrubs to drought stress The gas exchange parameters and leaf relative water content (RWC) were affectedby moderate stress, while chlorophyll fluorescence and chlorophyll content were onlyaffected by severe stress. Drought stress decreased net photosynthesis rate (Pn), stomatalconductance, light-use efficiency and RWC, and increased leaf temperature. Therespiration rates (Tr) were kept within a narrower range than Pn, resulting in aprogressively increased instantaneous water use effiecency (WUEi) under drought stress.Moreover, drought stress also affected the response curve of Pn to RAR, there was adepression light saturation point (Lsat) and maximum Pn (Pnmax) for moderate andsevere stressed seedling. However, diurnal changes of gas exchange parameters did notdiffer among water supplies although maximum daily Pn declined under severe stress.VISevere stress reduced Fv/Fm, Yield and qP while increased NPQ and chlorophyll content.Photosynthetic activity decreased during drought stress period due to stomatal andnon-stomatal limitations. The relative contribution of these limitations was associatedwith the severity of stress. The limitation to Pn was caused mainly by stomatal limitationunder moderate drought stress, and by the predominance of non-stomatal limitation undersevere stress. In this case, 40% FC water supply may be a non-stomatal limitation 5 Interspecific differences in drought tolerance of shrubs Three shrubs exhibited good performance throughout the experiment process, evenif at 20% FC treatment there were no any seedlings died, 80% FC water supply wassuitable for their establishment and growth. S. davidii minimized their water loss byreducing total leaf area and growth rate, as well as maintained higher RWC and Pncompared to the other two species under drought stress, thus they might be more tolerantto the drought stress than the other two species. On the contrary, it was found that C.polyantha and B. faberi var. microphylla had higher water loss because of their stomatalconductance and higher leaf area ratios. They reduced water loss with shedding theirleaves and changing leaf orientation under drought stress. Based on their responses, thestudied species could be categorized into two: (1) S. davidii with a tolerance mechanismin response to drought stress; (2) C. polyantha and B. faberi var. microphylla withdrought avoidance mechanism. These results indicated that slow-growing shrub speciesare better adapted to drought stress than intermediate or fast-growing species in present orpredicted drought conditions. Therefore, selecting rapid-growing species might leavethese seedlings relatively at a risk of extreme drought.
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,434,.:(1),(SPAD)NP,17.83%13.01%;NP,SPAD;SPAD99839,17.68%18.75%.(2),NP,NP13.03%23.17%,NP6.95%;64.01%~6.19%(P<0.05),39,16.60%~26.91%;,2.(3)Fv/FmFv/Fo,NP,NP998.,...
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(Open Top Chambers),(ZeamaysL.),NH3,,NH3(Fo),NH3,5(Fm)(Fv)(p<0.05),19FmFv;,NH32FmFvNH35,19,NH3,qNqP,NH3,NH3
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PHOTOSYSTEM-II; CHLOROPHYLL FLUORESCENCE; ULVA-ROTUNDATA; ELECTRON-TRANSPORT; FIELD EXPERIMENTS; O-2 EVOLUTION; QUANTUM YIELD; TEMPERATURE; MACROALGAE; RESPONSES
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Background: Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta). Herein, we documented these changes in this species of red algae. Results: In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks). During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII) activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Conclusions: Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within the young germling, the hetero-distribution of PSII photosynthetic capabilities might be due to the differences in cell functions.
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Physiological data from extreme habitat organisms during stresses are vital information for comprehending their survival. The intertidal seaweeds are exposed to a combination of environmental stresses, the most influential one being regular dehydration and re-hydration. Porphyra katadai var. hemiphylla is a unique intertidal macroalga species with two longitudinally separated, color distinct, sexually different parts. In this study, the photosynthetic performance of both PSI and PSII of the two sexually different parts of P. katadai thalli during dehydration and re-hydration was investigated. Under low-grade dehydration the variation of photosystems of male and female parts of P. katadai were similar. However, after the absolute water content reached 42%, the PSI of the female parts was nearly shut down while that of the male parts still coordinated well and worked properly with PSII. Furthermore, after re-hydration with a better conditioned PSI, the dehydrated male parts were able to restore photosynthesis within 1 h, while the female parts did not. It is concluded that in P. katadai the susceptibility of photosynthesis to dehydration depends on the accommodative ability of PSI. The relatively lower content of phycobiliprotein in male parts may be the cause for a stronger PSI after severe dehydration.
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In this work, the photosynthetic performances of Enteromorpha prolifera thalli collected from the surface and bottom of the sea of Qingdao sea area were studied with chlorophyll fluorescence and oxygraph technology. The samples with the highest photosynthetic activity among their kinds, the floating thalli from the sea surface of the south of the Qingdao Olympic Sailing Center and the sedimentary thalli from the mud surface of the bottom Tuandao bay, were chosen as representatives of surface thalli and bottom thalli, respectively. The results showed that the maximal PSII quantum yield of the floating thalli was significantly lower than the normal level although their photosynthetic activities were relatively high; the photosynthetic potential of the thalli form the mud surface was extremely low. Thus, it is indicated that the floating thalli are seriously stressed by their environment and the thalli from the mud surface are already dead or are dying. On the other hand, the results of the laboratory cultivation showed that the sedimentary thalli cannot regain normal photosynthetic activity even under normal illumination conditions. Thus, the thalli from the mud surface cannot become reproductive source of the alga even if they can reach sea surface again. Therefore, a preliminary conclusion can be reached that, up to mid-July 2008, the environmental conditions of the Qingdao sea area are not suitable for the growth of the alga E. prolifera and for this reason the biomass of E. prolifera, in the area, could be declining.
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The photosynthetic performances of regenerated protoplasts of Bryopsis hypnoides, which were incubated in seawater for 1, 6, 12, and 24 h, were studied using chlorophyll (Chl) fluorescence and oxygen measurements. Results showed that for the regenerated protoplasts, the pigment content, the ratios of photosynthetic rate to respiration rate, the maximal photosystem II (PSII) quantum yield (F-v/F-m), and the effective PSII quantum yield (I broken vertical bar(PSII)) decreased gradually along with the regeneration progress, indicated that during 24 h of regeneration there was a remarkable reduction in PSII activity of those newly formed protoplasts. We assumed that during the cultivation progress the regenerated protoplasts had different photosynthetic vigor, with only some of them able to germinate and develop into mature thalli. The above results only reflected the photosynthetic features of the regenerated protoplasts at each time point as a whole, rather than the actual photosynthetic activity of individual aggregations. Further investigation suggested a relationship between the size of regenerated protoplasts and their viability. The results showed that the middle-sized group (diameter 20-60 mu m) retained the largest number of protoplasts for 24 h of growth. The changes in F-v/F-m and I broken vertical bar(PSII) of the four groups of differently sized protoplasts (i.e. < 20, 20-60, 60-100, and > 100 mu m) revealed that the protoplasts 20-60 mu m in diameter had the highest potential activity of the photosynthetic light energy absorption and conversion for several hours.
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1321 84 9 DCM 6.41.0108tC/aVGPM250.5 OS5AFMFv/FmFv/Fm Fv/Fm0.37Fv/FmFv/Fm4 Fv/Fm3 Fv/FmFv/Fm Fv/FmFv/FmFv/FmNH4+NO3-PSiFv/Fm1 2 Fv/FmFv/Fm Fv/FmFv/Fm
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The extremely high level of solar radiation on the Qinghai-Tibet Plateau may induce photoinhibition and thus limit leaf carbon gain. To assess the effect of high light, we examined gas exchange and chlorophyll fluorescence for two species differing in light interception: the prostrate Saussurea superba and the erect-leaved Gentiana straminea. In controlled conditions with favorable water and temperature, neither species showed apparent photoinhibition in gas exchange measurements. In natural environment, however, their photosynthetic rate decreased remarkably at high light. Photosynthesis depression was aggravated under high leaf temperature or soil water stress. Relative stomatal limitation was much higher in S. superba than in G. straminea and it remarkably increased in the later species at midday when soil was dry. F-v/F-m as an indicator for photoinhibition was generally higher in S. superba than in the other species. F-v/F-m decreased significantly under high light at midday in both species, even when soil moisture was high. F-0 linearly elevated with the increment of leaf temperature in G. straminea, but remained almost constant in S. superba. Electron transport rate (ETR) increased with photosynthetically active photon flux density (PPFD) in S. superba, but declined when PPFD was high than about 1000 mumol m(-2) s(-1) in G. straminea. Compared to favorable environment, the estimated daily leaf carbon gain at PPFD above 800 mumol m(-2) s(-1) was reduced by 32% in S. superba and by 17% in G. straminea when soil was moist, and by 43% and 53%, respectively, when soil was dry. Our results suggest that the high radiation induces photoinhibition and significantly limits photosynthetic carbon gain, and the limitation may further increase at higher temperature and in dry soil.
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Ian M. Scott, Shannon M. Clarke, Jacqueline E. Wood and Luis A.J. Mur (2004). Salicylate accumulation inhibits growth at chilling temperature in Arabidopsis. Plant Physiology, 135(2), 1040-1049. RAE2008
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Continuous autoanalytical recordings of the axial distributions of dissolved nitrate, silicate and phosphate in the influent freshwater and saline waters of the Tamar Estuary, south-west England have been obtained. Short-term variability in the distributions was assessed by repetitive profiling at approximately 3-h intervals on a single day and seasonal comparisons were obtained from ten surveys carried out between June 1977 and August 1978. Whereas nitrate is always essentially conserved throughout the upper estuary, the silicate- and phosphate-salinity relationships consistently indicate a non-biological removal of these nutrients within the low (010%) salinity range. Attempts to quantify precisely the degree of removal and to correlate this with changes in environmental properties (pH, turbidity, chlorophyll fluorescence, salinity, freshwater composition) were mainly inconclusive due to short-term fluctuations in the riverine concentrations of silicate and phosphate advected into the reactive region and to the rapid changes in turbidity brought about by tidally-induced resuspension and deposition of bottom sediment.
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During viral infection of Emiliania huxleyi, laboratory studies have shown that photo-system (PS) II efficiency declines during the days post-infection and is thought to be associated with viral-induced interruption of electron transport rates between photosystems. However,measuring the impact of viral infection on PSII function in E. huxleyi populations from natural,taxonomically diverse phytoplankton communities is difficult, and whether this phenomenon occurs in nature is presently unknown. Here, chlorophyll fluorescence analysis was used to assess changes in PSII efficiency throughout an E. huxleyi bloom during a mesocosm experiment off the coast of Norway. Specifically, we aimed to determine whether a measurable suppression of the efficiency of PSII photochemistry could be observed due to viral infection of the natural E. huxleyi populations. During the major infection period prior to bloom collapse, there was a significant reduction in PSII efficiency with an average decrease in maximum PSII photochemical efficiency (Fv/Fm) of 17% and a corresponding 75% increase in maximum PSII effective absorption cross section(PSII); this was concurrent with a significant decrease in E. huxleyi growth rates and an increase in E. huxleyi virus (EhV) production. As E. huxleyi populations dominated the phytoplankton community and potentially contributed up to 100% of the chlorophyll a pool, we believe that the variable chlorophyll fluorescence signal measured during this period was derived predominantly from E. huxleyi and, thus, reflects changes occurring within E. huxleyi cells. This is the first demonstration of suppression of PSII photochemistry occurring during viral infection of natural coccolithophore populations.
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Coral reefs are of utmost ecological and economical importance but are currently in global decline due to climate change and anthropogenic disturbances. Corals, as well as other cnidarian species, live in symbiosis with photosynthetic dinoflagellates of the genus Symbiodinium. This relationship provides the cnidarian host with alternative metabolic pathways, as the symbionts translocate photosynthetic carbon to the animal. Besides this autotrophic nutrition mode, symbiotic cnidarians also take up organic matter from the environment (heterotrophy). The nutritional balance between auto- and heterotrophy is critical for the functioning, fitness and resilience of the cnidariandinoflagellate symbiosis. New methodological approaches were developed to better understand the role of auto- and heterotrophy in the ecophysiology of cnidarians associated with Symbiodinium, and the ecological implications of this trophic plasticity. Specifically, the new approaches were developed to assess photophysiology, biomass production of the model organism Aiptasia sp. and molecular tools to investigate heterotrophy in the cnidarian-dinoflagellate symbiosis. Using these approaches, we were able to non-invasively assess the photophysiological spatial heterogeneity of symbiotic cnidarians and identify spatial patterns between chlorophyll fluorescence and relative content of chlorophyll a and green-fluorescent proteins. Optimal culture conditions to maximize the biomass production of Aiptasia pallida were identified, as well as their implications on the fatty acid composition of the anemones. Molecular trophic markers were used to determine prey digestion times in symbiotic cnidarians, which vary between 1-3 days depending on prey species, predator species and the feeding history of the predator. This method was also used to demonstrate that microalgae is a potential food source for symbiotic corals. By using a stable isotope approach to assess the trophic ecology of the facultative symbiotic Oculina arbuscula in situ, it was possible to demonstrate the importance of pico- and nanoplanktonic organisms, particularly autotrophic, in the nutrition of symbiotic corals. Finally, we showed the effects of functional diversity of Symbiodinium on the nutritional plasticity of the cnidarian-dinoflagellate symbiosis. Symbiont identity defines this plasticity through its individual metabolic requirements, capacity to fix carbon, quantity of translocated carbon and the hosts capacity to feed and digest prey.
