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2752. Seasonal variation of photoinhibition of photosynthesis in bark from Populus tremula L.
- Creator:
- Solhaug, K. A. and Haugen, J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll fluorescence induction, irradiance, oxygen evolution, phellem, photosystem 2, poplar, quantum yyield, seasonal course, and tree age
- Language:
- Multiple languages
- Description:
- In the bark of Populus tremula L. photochemical efficiency of photosystem 2 (PS2) determined as Fv/Fm decreased during winter. The strongest reduction was found after cold periods. The degree of reduction depended on irradiance since the lowest levels of Fv/Fm were found on the sun-exposed side of the stem and below thin phellem. Therefore, photoinhibition was partly responsible for the reduction in Fv/Fm. The photochemical efficiency of PS2 recovered in late April about a month before the trees got leaves. In the laboratory, Fv/Fm recovered within about a week under low irradiance at 20 °C. Rapid recovery of photochemical efficiency of PS2 in the bark may be important to reduce respiratory loss of CO2 from the stem before the trees get leaves. and K. A. Solhaug, J. Haugen.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2753. Seasonal variation of photosynthesis and photosynthetic efficiency in Phalaenopsis
- Creator:
- Pollet, B., Steppe, K., Dambre, P., van Labeke, M.-C., and Lemeur, R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, chlorophyll fluorescence, CO2 assimilation, crassulacean acid metabolism, irradiance, photorespiration, temperature, and quantum yield
- Language:
- Multiple languages
- Description:
- Nowadays, a quest for efficient greenhouse heating strategies, and their related effects on the plant's performance, exists. In this study, the effects of a combination of warm days and cool nights in autumn and spring on the photosynthetic activity and efficiency of Phalaenopsis were evaluated; the latter, being poorly characterised in plants with crassulacean acid metabolism (CAM) and, to our knowledge, not reported before in Phalaenopsis. 24-h CO2 flux measurements and chlorophyll (Chl) fluorescence analyses were performed in both seasons on Phalaenopsis 'Hercules' exposed to relatively constant temperature regimes, 25.5/24.0°C (autumn) and 30/27°C (spring) respectively, and distinctive warm day/cool night temperature regimes, 27/20°C (autumn) and 36/24°C (spring), respectively. Cumulated leaf net CO2 uptake of the distinctive warm day/cool night temperature regimes declined with 10-16% as compared to the more constant temperature regimes, while the efficiency of carbon fixation revealed no substantial differences in both seasons. Nevertheless, a distinctive warm day/cool night temperature regime seemed to induce photorespiration. Although photorespiration is expected not to occur in CAM, the suppression of the leaf net CO2 exchange during Phase II and Phase IV as well as the slightly lower efficiency of carbon fixation for the distinctive warm day/cool night temperature regimes confirms the involvement of photorespiration in CAM. A seasonal effect was reflected in the leaf net CO2 exchange rate with considerably higher rates in spring. In addition, sufficiently high levels of photosynthetically active radiation (PAR) in spring led to an efficiency of carbon fixation of 1.06-1.27% which is about twice as high than in autumn. As a result, only in the case where a net energy reduction between the temperature regimes compensates for the reduction in net CO2 uptake, warm day/cool night temperature regimes may be recommended as a practical sustainable alternative. and B. Pollet ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2754. Seasonal water-use efficiency and chlorophyll fluorescence response in alpha grass (Stipa tenacissima L.) is affected by tussock size
- Creator:
- Ramírez, D. A. , Valladares, F., Domingo, F., and Bellot, J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- leaf area index, net photosynthetic rate, photoinhibition, photosystem 2, plant size, semiaridity, stomatal conductance, transpiration rate, and water stress
- Language:
- Multiple languages
- Description:
- Twelve randomly chosen Stipa tenacissima L. individuals were grouped into three tussock size classes, small (ST), medium (MT), and large (LT) with 5.6±0.8, 34.1±4.2, and 631.9±85.8 g of dry green foliar matter, respectively, in three plots with different S. tenacissima cover. Instantaneous (WUEi) and long-term (WUEl) water-use efficiencies were measured in two seasons of contrasting volumetric soil water content (early winter 21.0±0.8 % and summer 5.8±0.3 %). Maximum photochemical efficiency of photosystem 2 and stomatal conductance in summer assessed the extent of water and irradiance stress in tussocks of different size. WUEi was lower in MT and ST “water spender” strategies than in LT during the high water-availability season. In summer net photosynthetic rate and WUEi were higher and photoinhibition was lower in LT than in MT and ST. Significant spatial variability was found in WUEi. Water uptake was competitive in stands with denser alpha grass and more water availability in summer, reducing their WUEi. However, WUEl showed a rising tendency when water became scarce. Thus it is important to explicitly account for plant size in ecophysiological studies, which must be combined with demographic information when estimating functional processes at stand level in sequential scaling procedures. and D. A. Ramírez ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2755. Secondary structure estimation of recombinant psbH, encoding a photosynthetic membrane protein of cyanobacterium Synechocystis sp. PCC 6803
- Creator:
- Štys, D., Schoefberger, W., Halbhuber, Z., Ristvejova, J., Müller, N., and Ettrich, R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- CD spectroscopy, molecular dynamics calculations, NMR spectroscopy, photosystem 2, and protein folding
- Language:
- Multiple languages
- Description:
- The PsbH protein of cyanobacterium Synechocystis sp. PCC 6803 was expressed as a fusion protein with glutathione-S transferase (GST) in E. coli grown on a mineral medium enriched in 15N isotope. After enzymatic cleavage of the fusion protein, the 1H-15N-HSQC spectrum of PsbH protein in presence of the detergent β-D-octyl-glucopyranoside (OG) was recorded on a Bruker DRX 500 MHz NMR spectrometer equipped with a 5 mm TXI cryoprobe to enhance the sensitivity and resolution. Non-labelled protein was used for secondary structure estimation by deconvolution from circular dichroism (CD) spectra. Experimental results were compared with our results from a structural model of PsbH using a restraint-based comparative modelling approach combined with molecular dynamics and energetic modelling. We found that PsbH shows 34-38% α-helical structure (Thr36-Ser60), a maximum of around 15% of β-sheet, and 12-19% of β-turn. and D. Štys ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2756. Seed germination, seedling survival, and physiological response of sunflowers under saline and alkaline conditions
- Creator:
- Liu, J., Guo, W. Q., and Shi, D. C.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, alkali stress, ionic balance, osmotic adjustmen, and salt stress
- Language:
- Multiple languages
- Description:
- Salinization and alkalization of soil are widespread environmental problem and the alkali stress is more destructive than the effects caused by salt stress. To compare the mechanism of salt and alkali stresses, a sunflower variety (Helianthus annuus L. cv. Baikuiza 6) was tested under saline or alkaline conditions by mixing two neutral salts (NaCl and Na2SO4) or two alkaline salts (NaHCO3 and Na2CO3). The results showed that saline conditions differed greatly from alkaline conditions in their threshold intensities where sunflower can germinate, survive and grow. Under saline conditions, the emergence time was delayed, and the emergence rate and seedling survival rate also decreased with increasing salinity. However, under alkaline conditions, the rate of seedling survival decreased sharply but the emergence time and emergence rate did not change. In addition, the damaging effects of alkali stress on growth and photosynthesis were more severe than those of saline. In shoots, the main inorganic osmolyte and cation was K+ rather than Na+; the primary organic osmolytes were organic acid and soluble sugar rather than proline. Organic acid, NO3 -, and Cl- (only under saline condition) were the main source of anion. In addition, the osmotic adjustment and ion balance differed among sunflower roots, stems, and leaves. In conclusion, saline and alkaline conditions are two different stress conditions and there are special responses to two stress conditions for sunflower. and J. Liu, W. Q. Guo, D. C. Shi.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2757. Seed yield of soybeans with daytime or continuous elevation of carbon dioxide under field conditions
- Creator:
- Bunce, J. A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Glycine max, photosynthetically active radiation, precipitation, rainfall, stem, and vapor pressure deficit
- Language:
- Multiple languages
- Description:
- Some studies of responses of plants to elevated concentrations of carbon dioxide (EC) added CO2 only in the daytime, while others supplied CO2 continuously. I tested whether these two methods of EC treatments produced differences in the seed yield of soybeans. Tests were conducted for four growing seasons, using open top chambers, with soybeans rooted in the ground in field plots. One third of the chambers were flushed with air at the current ambient [CO2] (AC), one third had [CO2] 350 µmol mol-1 above ambient during the daytime (ECd), while one third had [CO2] 350 µmol mol-1 above ambient for 24 h per day (ECdn). ECdn increased seed yield by an average of 62 % over the four years compared with the AC treatment, while ECd increased seed yield by 34 %. Higher seed yield for ECdn compared with ECd occurred each year. In comparing years, the relative yield disadvantage of ECd decreased with increasing overall seed yield. On days with high water vapor pressure deficits, soybean canopies with ECd had smaller midday extinction coefficients for photosynthetically active radiation than canopies with ECdn, because of a more vertical leaf orientation. Hence the seed yield of soybean at EC varied depending on whether EC was also provided at night, with much greater yield stimulation for ECdn than for ECd in some years.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2758. Seeing is believing
- Creator:
- Govindjee and Nedbal, L.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll fluorescence
- Language:
- Multiple languages
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2759. Selective effects of H2O2 on cyanobacterial photosynthesis
- Creator:
- Drábková, M., Matthijs, H. C. P., Admiraal, W., and Maršálek, B.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll fluorescence induction, diatoms, fluorescence emission spectra, green algae, and species differences
- Language:
- Multiple languages
- Description:
- The sensitivity of phytoplankton species for hydrogen peroxide (H2O2) was analyzed by pulse amplitude modulated (PAM) fluorometry. The inhibition of photosynthesis was more severe in five tested cyanobacterial species than in three green algal species and one diatom species. Hence the inhibitory effect of H2O2 is especially pronounced for cyanobacteria. A specific damage of the photosynthetic apparatus was demonstrated by changes in 77 K fluorescence emission spectra. Different handling of oxidative stress and different cell structure are responsible for the different susceptibility to H2O2 between cyanobacteria and other phytoplankton species. This principle may be potentially employed in the development of new agents to combat cyanobacterial bloom formation in water reservoirs. and M. Drábková ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2760. Selenium delays leaf senescence in oilseed rape plants
- Creator:
- Rahmat, S., Hajiboland, R., and Sadeghzade, N.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- nitrát reduktázy, rychlost fotosyntézy, fluorescence chlorofylu, selen, řepka olejka, leaf photochemistry, nitrate reductase, photosynthetic rate, chlorophyll fluorescence, selenium, oilseed rape, 2, and 581
- Language:
- Multiple languages
- Description:
- Effect of selenium on leaf senescence was studied in oilseed rape plants treated with 10 μM Na2SeO4 at a rosette growth stage. In addition to developmental senescence, N deficiency and leaf detachment were used for induction of senescence. Nonphotochemical quenching declined in old leaves as senescence became more advancing but rose progressively in the plants supplied by Se. The total carbohydrate and protein pools decreased with leaf age, while increased by the Se treatment. However, during senescence induced by N deficiency, Se did not change remarkably the C and N metabolism, but delayed senescence mainly through protection of plants from photoinhibitory effects. After detachment, untreated leaves became chlorotic and necrotic, while the Se-treated ones remained fairly green. Our results demonstrated that Se delayed leaf senescence by a maintaining or even improving photochemical activities. During developmental senescence, the Se effect on the extending life span of the leaves was additionally linked to the metabolic regulation of senescence., S. Rahmat, R. Hajiboland, N. Sadeghzade., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public