Under natural conditions we found a significant variation in oxygen evolution rate (OER) in flag leaves of different rice genotypes during the grain filling stage. Cv. Roxinho showed the highest OER [42 µmol(O2) m-2 s-1], followed by BRS Taim, BRS Pelota, BRS Bojuru, IR58025B, BRS 6 Chui, and BR-IRGA 409, with 37.0, 34.0, 33.0, 31.8, 29.0, 28.0, and 27.6 µmol(O2) m-2 s-1, respectively. The lack of fertility in the male-sterile rice line IR58025A prolonged the photosynthetic capacity by at least 15 d when compared to the normal fertility found in the IR58025B line. No difference was observed in OER among first (flag) and second leaves in both IR58025A and IR58025B rice lines. and M. A. Bacarin ... [et al.].
Photosynthesis, as a fundamental element in the life process, is integrated in the evolution of living systems on the basis of hydrogen cycles on various hierarchic levels. Conversion of radiant energy enables the oxidation of water, whereby free oxygen accumulates in the atmosphere. Hydrogen is (reversibly) stored in organic materials formed under reductive CO2-fixation and by the incorporation of the other elements, which are necessary for living systems. All endergonic processes in living cells are finally driven by the energy released through the clean recombination of protons and electrons with oxygen to water. Duration of the stored energy and the complexity of the systems thus produced is correlated negatively with the conversion efficiency of the radiation energy. Entropy is a unifying principle in the evolution of living systems, inclusive human societies.
The effect of ethylenediurea (EDU) was tested using the chlorophyll (Chl) a fluorescence transient analysis, performed with JIP-test, to assess ambient ozone (O3) effects on photosynthesis of adult trees under natural conditions. Twelve adult European ash (Fraxinus excelsior L.) trees, known to be sensitive or tolerant to O3, determined by presence symptomatic (S) or absence asymptomatic (AS) trees of foliar symptoms in previous years, were treated either with distilled water containing 450 g m-3 EDU or with distilled water. Once a month across the growing season [the accumulated exposure over a threshold of 40 nmol(O3) mol-1 was 32.49 µmol mol-1 h-1], Chl a fluorescence transients were measured in vivo on dark-adapted leaves of 1-year-old labeled shoots, from the lower crown part. Twenty-five parameters were calculated. The maximum quantum yield of primary photochemistry (ϕPo or Fv/Fm) did not differentiate between S-and AS-trees, while increased Chl content and de-excitation rates suggested compensation of O3 injury in S-trees. Seasonal reductions in absorbing fluxes and increase in heat and fluorescence dissipation processes was due to leaf ageing and drought, the latter suggesting water deficit influenced Chl a fluorescence stronger than ambient O3 exposure. AS-trees showed elevated probability of connectivity among photosystem 2 units, a mechanism to stimulate energy dissipation and reduce photo-oxidative injury. EDU prevented the inactivation of reaction centers. This slight effect does not warrant EDU as a tool to assess O3 effects on photosynthesis, while the JIP-test is suggested for a quantitative assessment in adult trees. and N. Contran ... [et al.].
Ozone (O3) is important air pollutant inducing severe losses of horticultural production. Cultivars of the same species, but with different leaf colors, may differ in their ozone sensitivity. However, it has not been clarified yet if different leaf coloration influences such a sensitivity. In this study, two purple-leafed and two green-leafed cultivars of Pakchoi were selected for ozone fumigation (240 ± 20 nmol mol-1, 09:00-16:00 h). Elevated O₃ decreased chlorophyll content, increased anthocyanin (Ant) content, damaged cell membrane integrity, enhanced antioxidative enzyme activities, depressed photosynthetic rate (PN) and stomatal conductance (gs), inhibited maximal quantum yield (Fv/Fm) and effective quantum yield [YII] of PSII photochemistry, and caused visible injury. Purple-leafed cultivars with higher Ant contents were more tolerant than green-leafed cultivars as indicated by lower relative enhancement in malondialdehyde content and lower relative losses in PN, gs, Fv/Fm, and YII. The higher ability to synthesize Ant in the purple-leafed cultivars contributed to their higher photoprotective ability., L. Zhang, S. Xiao, Y. J. Chen, H. Xu, Y. G. Li, Y. W. Zhang, F. S. Luan., and Obsahuje bibliografii
Our experiment was conducted in order to find out effects of paclobutrazol (PBZ; 30 μl l-1) on morphology, photosynthetic process, and stress markers under water surplus and deficit conditions in several wheat genotypes. Study revealed that relative water content (RWC), photosynthetic rate, and maximal quantum yield of PSII (FV/FM) was improved after a PBZ application both under irrigation and water deficit across the genotypes, while the stomatal conductance was reduced. Further, the application of PBZ led to reduced leaf area in wheat genotypes. Moreover, a proline content was higher in the wheat genotypes under water stress as compared to the irrigated plants. The application of PBZ led to downregulation of the proline content under water deficit, while there was no significant change in the content and activity under irrigation with or without the PBZ treatment. These findings indicated that due to the application of PBZ the wheat genotypes might sense a lower stress level (indicated by the proline content) and better drought tolerance (according to RWC and photosynthetic characteristics)., S. K. Dwivedi, Ajay Arora, S. Kumar., and Obsahuje bibliografii
The article brings brief information about the elementary manuscript holdings of the Paris National Library focusing on the occurrence of albums, especially those containing entries connected with Bohemia. As well as a series of albums belonging to foreigners who travelled to Bohemia or were given entries by Czech students on their sojourns abroad, the collection houses a rather exceptional manuscript – the album of Frederick V. The voluminous manuscript in sumptuous binding, the copy of which was gained by the National Museum Library, is worth a more detailed investigation in international context too. The study of the albums focused on finding out Latin occasional poetry connected with Bohemia, but its results are rather poor.
When we apply ecological models in environmental management, we must assess the accuracy of parameter estimation and its impact on model predictions. Parameters estimated by conventional techniques tend to be nonrobust and require excessive computational resources. However, optimization algorithms are highly robust and generally exhibit convergence of parameter estimation by inversion with nonlinear models. They can simultaneously generate a large number of parameter estimates using an entire data set. In this study, we tested four inversion algorithms (simulated annealing, shuffled complex evolution, particle swarm optimization, and the genetic algorithm) to optimize parameters in photosynthetic models depending on different temperatures. We investigated if parameter boundary values and control variables influenced the accuracy and efficiency of the various algorithms and models. We obtained optimal solutions with all of the inversion algorithms tested if the parameter bounds and control variables were constrained properly. However, the efficiency of processing time use varied with the control variables obtained. In addition, we investigated if temperature dependence formalization impacted optimally the parameter estimation process. We found that the model with a peaked temperature response provided the best fit to the data., H. B. Wang, M. G. Ma, Y. M. Xie, X. F. Wang, J. Wang., and Obsahuje bibliografii
We used Y-plant, a computer-based model of plant crown architecture analysis, to simulate effects of defoliation on daily canopy carbon gain in Psychotria marginata (Rubiaceae) plants under two contrasting irradiances. Five levels of defoliation were simulated using two different types of leaf blade damage. Compensatory increases in photon-saturated photosynthetic capacity (Pmax) of 25, 50, and 100 % defoliation were also simulated. In all simulations daily photon capture and CO2 assimilation increased with defoliation. However, without a compensatory response, daily canopy carbon gain also decreased with defoliation. Under high irradiance, reduction in daily canopy carbon gain was less than what would be expected if the response was proportional to leaf area reduction. Thus, 25 and 50 % defoliation resulted in only 20 and 41 % of daily canopy carbon gain reduction, respectively. In the scenario where 25 % of the leaf area was removed, if the Pmax value was increased by 25 %, the remaining leaves compensated for 94 % of the daily canopy carbon relative to an undamaged non-compensated plant. At the same defoliation level, incrementing Pmax values by 50 and 100 % resulted in overcompensation. Hence, because the increment of daily photon capture and CO2 assimilation after defoliation was more a passive consequence of the reduction in leaf area than an active response, under the conditions tested photosynthetic compensation could be only possible through an active mechanism such as the increment of Pmax values. and D. Gálvez, A. Cohen-Fernández.