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.
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
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
Coral reef bleaching is a global phenomenon poorly understood today. We investigated during 7 d the photosynthetic behaviour of symbionts of coral reef and temperate foraminifers in hospite, by means of the JIP-test. By this screening test the fast fluorescence rise O-J-I-P, measured by a Plant Efficiency Analyser (PEA) with 10 µs time resolution and 12 bit signal resolution, was analysed. It informs about the structure and function of photosystem 2 being at different physiological states established by adaptation to different irradiance and temperature. The test needs a measuring time in vivo of only 1 to 5 s, and thus many samples can be analysed. The measurements can be done continuously even on a single cell in a test tube or on the reef. The reef foraminifers tested here were Amphistegina and Amphisorus, freshly collected in Mauritius. As a temperate foraminifer, Sorites from the Mediterranean Sea was tested. The cells are very sensitive to slight temperature changes (25 to 32 °C). The comparison showed that the more the foraminifers live in an environment with constant temperature the less they are able to respond to temperature changes and, thus, the less they can adapt. Rising the temperature increases in general the sensitivity to different stress factors, such as high irradiance, pH, CO2, etc. After the test series, the cells recovered fully and were kept in an aquarium for long time observation. and R. J. Strasser, M. Tsimilli-Michael, M. Pêcheux.
Light is a limiting factor in plant establishment and growth in the understory of forests. In this paper, we assessed acclimation capacity of Siparuna guianensis, an early secondary successional species. We used seedlings and saplings in three regeneration areas with different irradiance regimes to determine the traits that confer photoplasticity. We examined whether these traits differ at different developmental stages. Anatomical characteristics, photochemical efficiency, photosynthetic capacity, and growth were analyzed. Multivariate component analysis revealed the formation of six clusters: three for seedlings (one for each regeneration area) and three for saplings (following the same pattern of seedlings, considering the area). Increased irradiance favored photosynthetic performance, independently of the developmental stage. The same trend was observed for most data on chlorophyll (Chl) a fluorescence and the ratios of net photosynthetic rate/intercellular CO2 concentration (PN/Ci) and PN/PPFD. No parameter indicated photoinhibition stress. The CO2- and light-response curve data indicated that seedlings were already acclimated to tolerate variation in irradiance. Anatomical adaptations, such as thickness of leaf blade and of adaxial cuticle, were observed in individuals growing in areas with higher irradiation. Thinning of spongy parenchyma and higher investment into a plant height were observed in seedlings, possibly due to the vertical stratification of CO2 and light in the understory; because light is a more limiting resource than CO2 in the lower stratum of the forest. Photoplasticity in S. guianensis is associated with a set of morphological, anatomical, photochemical, and biochemical traits, whereas biochemical performance is best acclimated to variation in irradiance. These traits differed in seedlings and saplings but they were modulated mainly by irradiance in both developmental stages., T. O. Vieira, M. S. O. Degli-Esposti, G. M. Souza, G. R. Rabelo, M. Da Cunha, A. P. Vitória., and Obsahuje bibliografii
To investigate the photoprotection of energy dissipation and water-water cycle, a C3 euhalophytic herb, Suaeda salsa L., was exposed either to chilling temperature (4°C) accompanied by moderate irradiance (600 μmol m-2 s-1) (CM) and/or to chilling temperature (4°C) accompanied by low irradiance (100 μmol m-2 s-1) (CL). During chilling stress, both the maximal photochemical efficiency of PSII (Fv/Fm) and the oxidizable P700 decreased in S. salsa leaves either under CM or CL, which indicated the severe photoinhibition. Relative to Fv/Fm, the oxidizable P700 decreased markedly under CL, which indicated that PSI was more sensitive to CL treatment than PSII. Initial fluorescence, number of closed PSII centers, and nonphotochemical quenching increased under CM, but more markedly under CL in S. salsa leaves. Activity of superoxide dismutase and ascorbate peroxidase was higher under CM than that under CL. The production of reactive oxygen species (ROS) decreased first and then increased under both treatments, but the content of O2.- and H2O2 was higher under CL than that under CM after 12 h of chilling stress. These results suggested that photoinhibition in S. salsa might be related to the accumulation of reactive oxygen species (ROS) induced by excess energy. The water-water cycle could not dissipate energy efficiently under CL, which caused the great accumulation of ROS., N. Sui., and Obsahuje bibliografii
Gas exchange and chlorophyll fluorescence parameters of PSII were analyzed in the bracts and leaves of cotton plants after anthesis. Photosynthetic activity and photorespiration were measured in the leaves and bracts of cotton grown under either normal or reduced water-saving drip irrigation. The photosynthetic performance, amount of chlorophyll and Rubisco, and net photosynthesis were greater in the bracts than that in the leaves under water stress. The actual photochemical efficiency of PSII decreased in both the bracts and leaves after anthesis under reduced irrigation. However, the decrease was smaller in the bracts than in the leaves, indicating that the bracts experienced less severe photoinhibition compared to the leaves. The greater drought tolerance of bracts could be related to differences in relative water content, instantaneous water-use efficiency, and photorespiration rate. The ratio of photorespiration to net photosynthesis was much higher in the bracts than in leaves. Furthermore, water deficiency (due to the water-saving drip irrigation) had no significant effect on that ratio in the bracts. We hypothesized that photorespiration in the bracts alleviated photoinhibition and maintained photosynthetic activity., C. Zhang, D.-X. Zhan, H.-H. Luo, Y.-L. Zhang, W.-F. Zhang., and Obsahuje seznam literatury
Časopis, který vydává Ústav experimentální botaniky AV ČR, publikuje články zaměřené výhradně na studium fotosyntézy. Základní proces probíhající v rostlinách a některých dalších organismech zkoumá z pohledu biofyziky, molekulární biologie, biochemie, fyziologie, a ekologie. Častými tématy článků jsou struktura fotosyntetického aparátu, biochemické a biofyzikální mechanismy fotosyntetických reakcí, ultrastruktura chloroplastů, složení fotosyntetických pigmentů, měření rychlosti fotosyntézy a stanovení fotosyntetické produkce. Významné je i ovlivnění fotosyntetických procesů různými abiotickými a biotickými stresy včetně těch souvisejících s globální změnou klimatu (zvýšená koncentrace CO2, oteplování, sucho, UV záření, aj.). and Ivana Štětinová.