Number of results to display per page
Search Results
1112. Elevated CO2 and temperature differentially affect photosynthesis and resource allocation in flag and penultimate leaves of wheat
- Creator:
- Pérez, P., Zita, G., Morcuende, R., and Martínez-Carrasco, R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- acclimation, ribulose-1,5-bisphosphate carboxylase, oxygenase, temperature, and Triticum aestivum
- Language:
- Multiple languages
- Description:
- Differences in acclimation to elevated growth CO2 (700 µmol mol-1, EC) and elevated temperature (ambient +4 °C, ET) in successive leaves of wheat were investigated in field chambers. At a common measurement CO2, EC increased photosynthesis and the quantum yield of electron transport (Φ) early on in the growth of penultimate leaves, and later decreased them. In contrast, EC did not change photosynthesis, and increased Φ at later growth stages in the flag leaf. Contents of chlorophyll (Chl), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO), and total soluble protein were initially higher and subsequently lower in penultimate than flag leaves. EC decreased RuBPCO protein content relative to soluble protein and Chl contents throughout the development of penultimate leaves. On the other hand, EC initially increased the RuBPCO:Chl and Chl a/b ratios, but later decreased them in flag leaves. In the flag leaves but not in the penultimate leaves, ET initially decreased initial and specific RuBPCO activities at ambient CO2 (AC) and increased them at EC. Late in leaf growth, ET decreased Chl contents under AC in both kinds of leaves, and had no effect or a positive one under EC. Thus the differences between the two kinds of leaves were due to resource availability, and to EC-increased allocation of resources to photon harvesting in the penultimate leaves, but to increased allocation to carboxylation early on in growth, and to light harvesting subsequently, in the flag leaves. and P. Pérez ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1113. Elevated CO2 concentration enhances the role of the ear to the flag leaf in determining grain yield of wheat
- Creator:
- Zhu, C.-W., Zhu, J.-G., Liu, G., Zeng, Q., Xie, Z.-B., Pang, J., Feng, Z.-Z., Tang, H.-Y., and Wang, L.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- net photosynthetic rate and Triticum aestivum
- Language:
- Multiple languages
- Description:
- Net photosynthetic rate (PN) of ear and flag leaf during grain filling stage and grain yield of plants with non-darkened or darkened flag leaf or darkened ear were examined in two different CO2 concentrations: ambient (AC) and AC+200 µmol mol-1 (EC). Ear showed much higher enhancement (56 %) of PN than flag leaf (23 %) under EC. Moreover, CO2 enrichment shortened the photosynthetic duration of flag leaf relative to ear. In this way the ratio of ear to flag leaf contribution to grain yield increased from 1.18 (AC) to 1.39 (EC). and C.-W. Zhu ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1114. Elevated CO2 increased photosynthesis and yield without decreasing stomatal conductance in broomcorn millet
- Creator:
- Hao, X. Y., Li, P., Li, H. Y., Zong, Y. Z., Zhang, B., Zhao, J. Z., and Han, Y. H.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fluorescence chlorofylu, výměna plynu, obohacování o CO2, efektivita využívání vody, proso seté, chlorophyll fluorescence, CO2 enrichment, gas exchange, water-use efficiency, 2, and 581
- Language:
- Multiple languages
- Description:
- Broomcorn millet (Panicum miliaceum L.) is one of the important C4 crops in the semiarid regions of northern China. It is a close relative of biofuel crop switchgrass. Yet, there is no information on how these crops might respond to a climate change in China. In order to gain insight into such a response, we studied the effect of elevated CO2 concentration (EC) on broomcorn millet. The changes in leaf photosynthesis, chlorophyll fluorescence, morphological parameters, biomass and yield in response to EC [i.e., + 200 µmol(CO2) mol-1] over two years were determined at the open-top chamber (OTC) experimental facility in north China. EC increased net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, instantaneous transpiration efficiency, effective quantum yield of PSII photochemistry, and photochemical quenching coefficient of fully expanded flag leaves. Maximal quantum yield of PSII photochemistry declined under EC in 2013, but was not affected in 2014. EC significantly decreased intrinsic efficiency of PSII in 2013, but increased in 2014. Leaf nonphotochemical quenching decreased under EC both in 2013 and 2014. EC significantly enhanced the aboveground biomass and yield by average of 31.4 and 25.5% in both years, respectively. The increased yield of broomcorn millet under EC occurred due to the enhanced number of grains per plant. We concluded that photosynthesis of broomcorn millets was improved through increased stomatal conductance in leaves under EC, which led to an increase in height, stem diameter, aboveground biomass, and yield. This study extends our understanding of the response of this ancient C4 crop to elevated CO2 concentration., X. Y. Hao, P. Li, H. Y. Li, Y. Z. Zong, B. Zhang, J. Z. Zhao, Y. H. Han., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1115. Elevated CO2 mitigates the adverse effects of drought on daytime net ecosystem CO2 exchange and photosynthesis in a Florida scrub-oak ecosystem
- Creator:
- Li, J. H., Johnson, D. P., Dijkstra, P., Hungate, B. A., Hinkle, C. R., and Drake, B. G.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- air vapor pressure deficit, net ecosystem CO2 exchange, open-top chamber, Quercus myrtifolia, and stomatal conductance
- Language:
- Multiple languages
- Description:
- Drought is a normal, recurrent feature of climate. In order to understand the potential effect of increasing atmospheric CO2 concentration (Ca) on ecosystems, it is essential to determine the combined effects of drought and elevated Ca (EC) under field conditions. A severe drought occurred in Central Florida in 1998 when precipitation was 88 % less than the average between 1984 and 2002. We determined daytime net ecosystem CO2 exchange (NEE) before, during, and after the drought in the Florida scrub-oak ecosystem exposed to doubled Ca in open-top chamber since May 1996. We measured diurnal leaf net photosynthetic rate (PN) of Quercus myrtifolia Willd, the dominant species, during and after the drought. Drought caused a midday depression in NEE and PN at ambient CO2 concentration (AC) and EC. EC mitigated the midday depression in NEE by about 60 % compared to AC and the effect of EC on leaf PN was similar to its effect on NEE. Growth in EC lowered the sensitivity of NEE to air vapor pressure deficit under drought. Thus EC would help the scrub-oak ecosystem to survive the consequences of the effects of rising atmospheric CO2 on climate change, including increased frequency of drought, while simultaneously sequestering more anthropogenic carbon. and J. H. Li ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1116. Elucidation of the primary events in photosynthesis. Novel Insights based on enolisation and iminium Involvement with pheophytin in photosystem 2
- Creator:
- Kovacic, P.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll, electron transfer, electrostatics, and enigma elucidation
- Language:
- Multiple languages
- Description:
- Pheophytin (Pheo) is structurally constituted as to make possible certain reactions, previously given very little attention, which appear to play crucial roles in the initial electron transfer (ET) processes. The transformations involve enolisation with subsequent formation of mono- and di-iminium cations at the Pheo core. The important impact of these ions on ET from chlorophyll (Chl) to Pheo and then to quinone are evaluated. These insights rationalise the long-standing enigmas of fast transfer, across gap ET, activation-less aspect, and essential lack of reversibility. Comparisons are made to other important areas of iminium involvement, e.g. chemistry of vision, polyaniline doping, and DNA alkylation.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1117. Energetic aspects of chlorophyll biosynthesis
- Creator:
- Averina, N.G., Walter, G., and Hoffmann, P.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- The formation of S-aminolevulmic acid (ALA), energy-dependent steps ffom ALA to protoporphyrin IX (Proto) and from Proto to protochlorophyllide (PChlide) formation, the roles of NADPH in PChlide photoreduction and geranylgeraniol hydrogenation, the source of adenylates and reduced pyridine nucleotides for the reactions of chlorophyll biosynthesis, and the compartmentation and interrelationships of porphyrin biosynthesis pathways are reviewed.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1118. Energy dissipation and antioxidant enzyme system protect photosystem II of sweet sorghum under drought stress
- Creator:
- Guo, Y. Y., Tian, S. S., Liu, S. S., Wang, W. Q., and Sui, N.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- voda, water, antioxidační enzymy, chlorofylová fluorescence, environmentální stres, čirok dvoubarevný, antioxidant enzymes, chlorophyll fluorescence, environmental stress, sorghum bicolor, 2, and 581
- Language:
- Multiple languages
- Description:
- The effect of drought stress on energy dissipation and antioxidant enzyme system in two sweet sorghum inbred lines (M-81E and Roma) was investigated. Results showed that the germination indicator increased more in M-81E than that in Roma under rehydration. Under drought stress, both the maximal photochemical efficiency of PSII (Fv/Fm) and oxidoreductive activity (ΔI/I0) of Roma decreased more than those in M-81E. Relative to Fv/Fm, the ΔI/I0 decreased markedly, which indicated that PSI was more sensitive to drought stress than PSII. Increases in the reduction state of QA (1-qp), nonphotochemical quenching (NPQ) and minimal fluorescence yield of the dark-adapted state (F0) were greater in Roma than those in M-81E; meanwhile, the H2O2 content was lower in M-81E than that in Roma. Our results suggested that the photoinhibition might be related to the accumulation of reactive oxygen species (ROS). The antioxidant enzyme system and energy dissipation of M-81E could respectively increase drought tolerance by eliminating ROS and excess energy more efficiently than that of Roma., Y. Y. Guo, S. S. Tian, S. S. Liu, W. Q. Wang, N. Sui., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1119. Energy transfer of aromatic amino acids in photosystem 2 core antenna complexes CP43 and CP47
- Creator:
- Qu, Y.-G., Qin, X.-C., Wang, W.-F., Li, L.-B., and Kuang, T.-Y.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorpton, β-carotene, chlorophyll, fluorescence, model, proteins, tryptophan, and tyrosine
- Language:
- Multiple languages
- Description:
- Energy transfer of aromatic amino acids in photosystem 2 (PS2) core antenna complexes CP43 and CP47 was studied using absorption spectroscopy, fluorescence spectroscopy, and the 0.35 nm crystal structure of PS2 core complex. The energy of tyrosines (Tyrs) was not effectively transferred to tryptophans (Trps) in CP43 and CP47. The fluorescence emission spectrum of CP43 and CP47 by excitation at 280 nm should be a superposition of the Tyr and Trp fluorescence emission spectra. The aromatic amino acids in CP43 and CP47 could transfer their energy to chlorophyll (Chl) a molecules by the Dexter mechanism and the Föster mechanism, and the energy transfer efficiency in CP47 was much higher than that in CP43. In CP47 the Föster mechanism must be the dominant energy transfer mechanism between aromatic amino acids and Chl a molecules, whereas in CP43 the Dexter mechanism must be the dominant one. Hence solar ultraviolet radiation brings not only damages but also benefits to plants. and Y. G. Qu .... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1120. Energy-dependent quenching of chlorophyll-a-fluorescence: the involvement of proton-calcium exchange at photosystem 2
- Creator:
- Krieger, A. and Weis, E.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- The pH-dependent quenching of chlorophyll (Chl) fluorescence (the high energy quenching) was characterized by stationary Chl-a-fluorescence in the thylakoid membranes and photosystem (PS) 2 preparations. The variable part of fluorescence was quenched, when the pH in the thylakoid lumen decreased below 5.5, i.e., at high ApH. This quenching was caused by an inhibition of electron donation from the manganese cluster to the reaction centre of PS 2. The pH response of quenching suggested that a 1 H'''-transition with an apparent pK of 4.7 was involved. Parallel to quenching at low pH, a Ca^‘'‘-release was measured (1 Ca^'*' per 200 Chl). When the ApH relaxed and the pH on the lumen side increased again, fluorescence recovered provided Ca^'*' was present (Kd = 100 pM). Both the quenching at low pH and the reactivation at pH > 5.5 are light-dependent processes. In the presence of high concentration of extemal Ca^"^, fluorescence recovered even at low pH. Inhibition of the donor-side of PS 2 directly affected the acceptor-side of PS 2, as seen by a shift of the redox potential of Qa from -120 mV (pH 7.0) to +40 mV (pH 4.2). We propose that at high ApH (7) the water splitting side is inactivated by release of Ca from a high afflnity binding site, and (2) Qa is converted to a high-potential form. Excitatíon energy is then dissipated at the PS 2 reaction centres by a recombination reaction between donor and acceptor side. As a result, Qa (and the intersystem electron transport chain) remains oxidized, even in the excessive light.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public