The recognition of aquatic organisms plays a crucial role in the monitoring of the pollution and for the adoption of rapid preventive actions. A compact microscopic optical imaging system is proposed in order to acquire and treat the multibands fluorescence of several pigments in phytoplankton organisms. Two algorithms for automatic recognition of phytoplankton were proposed with a minimum number of calibration parameters. The first algorithm provides a morphological recognition based on "watershed" segmentation and Fourier descriptors, while the second one builds fluorescence pigment images by "k-means" partition of intensity ratios. The operation of these algorithms was illustrated by the study of two different organisms: a cyanobacteria (Dolichospermum sp.) and an alga (Cladophora sp.). The family and the genus of these organisms were then classified into a database which is independent of the size, the orientation and the position of the specimens in the images., M. Lauffer, F. Genty, S. Margueron, J. L. Collette., and Obsahuje bibliografii
The riparian forests along the Tarim River, habitats for Populus euphratica establishment, are subjected to frequent flooding. To elucidate adaptive strategies that enable this species to occupy the riparian ecosystem subjected to seasonal or permanent water-logging, we examined functional characteristics of plant growth, xylem water relations, leaf gas exchange, chlorophyll (Chl) content and fluorescence, soluble sugar and malondialdehyde (MDA) content in P. euphratica seedlings flooded for 50 d. Although flooded seedlings kept absorbing carbon throughout the experiment, their shoot and root growth rates were lower than in non-flooded seedlings. The reduced leaf gas exchange and quantum efficiency of PSII of flooded seedlings resulted possibly from the reduction in total Chl content. Content of soluble sugar and malondialdehyde in leaves were higher in flooded than in control seedlings. Soil flooding induced hypertrophy of lenticels and increased a stem diameter. These responses were responsible for species survival as well as its success in this seasonally flooded riparian zone. Our results indicate that P. euphratica is relatively flood-tolerant due to a combination of morphological, physiological, and biochemical adjustments, which may support its dominance in the Tarim riparian forest., B. Yu, C. Y. Zhao, J. Li, J. Y. Li, G. Peng., and Obsahuje bibliografii
Natural and commercial Salix clones differ in their ecophysiological response to Zn stress This study was carried out to determine the effect of different zinc concentrations on the ecophysiological response of Salix clones: four commercial clones (“1962”, “1968”, “Drago”, and “Levante”) selected for short rotation coppice, and one natural clone, “Sacco”, obtained from a contaminated area. Gas exchanges, chlorophyll a fluorescence (JIP-test), relative chlorophyll content, and biometric parameters were measured in plants grown for fifteen days in soil containing Zn concentrations of 0, 300, 750, and 1,500 mg(ZnCl2) kg-1. Ecophysiological response to metal stress differed in dependence on the Zn concentration and clone. At the low Zn concentration (300 mg kg-1), the absence of any significant reductions in parameters investigated indicated an efficient plant homeostasis to maintain the metal content within phytotoxic limits. Stomatal limitation, observed at 750 and 1,500 mg kg-1, which was found in all clones after three days of the treatment, might be caused by indirect effects of metal on guard cells. Among commercial clones, “Drago” was more sensitive to Zn stress, showing inhibition of growth, while “1962” clone showed a downregulation of PSII photochemistry following the slowdown in the Calvin-Benson cycle. On the contrary, the natural Salix clone (“Sacco”) performed better compared to the other clones due to activation of a photosynthetic compensatory mechanism., A. Bernardini, E. Salvatori, S. Di Re, L. Fusaro, G. Nervo, F. Manes., and Obsahuje seznam literatury
Twentieth-century photosynthesis research had strong roots in Germany, with the cell physiologist Otto H. Warburg being among its most influential figures. He was also one of the few scientists of Jewish ancestry who kept his post as a director of a research institution throughout the Nazi period. Based on archival sources, the paper investigates Warburg’s fate during these years at selected episodes. He neither collaborated with the regime nor actively resisted; he was harrassed by bureaucracy and denunciated to the secret police, but saved by powerful figures in economy, politics, and science. Warburg reciprocated this favour with problematic testimonies of political integrity after 1945. Warburg’s case, thus, defies wellestablished notions of how scientists in Germany lived and worked during the Nazi regime, and, therefore, helps provide a more nuanced perspective on this theme., K. Nickelsen., and Obsahuje bibliografické odkazy
In this brief communication we provide an estimate of the part of the incident solar energy used for oxygen evolution as well as the time, in years, needed for the generation of the present amount of molecular oxygen in the biosphere by photosynthesis on land and in the ocean. We find this to be ~3,000 yr. We also find that the ocean produces 22% more oxygen than the land surface., A. Yu. Borisov, L. O. Björn., and Obsahuje bibliografické odkazy
The variable fluorescence at the maximum Fm of the fluorescence induction (Kautsky) curve is known to be substantially suppressed shortly after light adaption due to nonphotochemical qE quenching. The kinetic pattern of the dark decay at Fm consists of three components with rates ~20, ~1, and ~0.1 s-1, respectively. Light adaptation has no or little effect on these rate constants. It causes a decrease in the ratio between the amplitudes of the slow and fast one with negligible change in the small amplitude of the ultra-slow component. Results add to evidence for the hypothesis that the dark-reversible decrease in variable fluorescence accompanying light adaptation during the P-S phase of the fluorescence induction curve is due to an alteration in nonphotochemical qE quenching caused by changes in the trans-thylakoid proton motive force in response to changes in the proton conductance gH+ of the
CF0-channel of the CF0·CF1·ATPase., W. J. Vredenberg., and Obsahuje bibliografické odkazy
Calmodulin (CaM) is a highly conserved calcium sensor protein associated with chilling tolerance in living organisms. It has four EF-hand domains for binding of four Ca2+, two of them located in the N-terminus, and the other two in the C-terminus. A notothenioid CaM gene fragment (CaMm), which only codes for N-terminus of CaM (with two EF-hand domains), was introduced into Nicotiana benthamiana. Effects of its overexpression on chilling tolerance in plants were explored. During 4◦C or 0◦C chilling treatment, both CaMm and CaM transgenic plants showed higher PSII maximum quantum yield, actual quantum yield, and soluble protein content, lower electrolyte leakage and malondialdehyde content than that of the control. The changes in these physiological indices were comparable between the CaMm and CaM transgenic plants during the treatments. These results indicate that the N-terminus of calmodulin is likely the key functional domain involved in the adaptive response to cold stress., T. J. Zhang, L. J. Pan, Q. Huang, L. H. Zhu, N. Yang, C. L. Peng, L. B. Chen., and Obsahuje seznam literatury
Drought impacts severely crop photosynthesis and productivity. Development of transgenic rice overexpressing maize phosphoenolpyruvate carboxylase (PEPC) is a promising strategy for improving crop production under drought stress. However, the molecular mechanisms of protection from PEPC are not yet clear. The objective of this study was: first, to characterize the response of individual photosynthetic components to drought stress; second, to study the physiological and molecular mechanisms underlying the drought tolerance of transgenic rice (cv. Kitaake) over-expressing maize PEPC. Our results showed that PEPC overexpressing improved the ability of transgenic rice to conserve water and pigments during drying as compared to wild type. Despite the fact that drought induced reactive oxygen species and damaged photosystems (especially, PSI) in both lines, higher intercellular CO2 concentration protected the photosynthetic complexes, peptides, and also ultrastructure of thylakoid membranes against the oxidative damage in transgenic rice. In conclusion, although photosynthetic apparatus suffered an inevitable and asymmetric impairment during drought conditions, PEPC effectively alleviated the oxidative damage on photosystems and enhanced the drought tolerance by increasing intercellular CO2 concentration. Our investigation provided critical clues for exploring the feasibility of using C4 photosynthesis to increase the yield of rice under the aggravated global warming., W. J. Shen, G. X. Chen, J. G. Xu, Y. Jiang, L. Liu, Z. P. Gao, J. Ma, X. Chen, T. H. Chen, and C. F. Lv., and Obsahuje seznam literatury
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