V naší studii se zabýváme zpěvní a hnízdní aktivitou ptáků v tropickém deštném lese Kamerunské hory v západní Africe. Ukázali jsme, že toto na první pohled stálé prostředí vykazuje výraznou sezonalitu v množství srážek ovlivňujících dostupnost potravy. Důsledkem je variabilní sezónní aktivita ptačího společenstva, zejména různých potravních guild. Sezonalita prostředí i ptačího společenstva se mění také s nadmořskou výškou., The aim of our study, conducted in the Republic of Cameroon (Africa), was to examine the singing and breeding activity of birds in a tropical rain forest. We have shown that this otherwise stable environment exhibits a distinct seasonality in rainfall, resulting in seasonal activity of bird communities, especially of various feeding guilds. Seasonality of environment and breeding of bird communities also changed with the altitude (tested on the Mount Cameroon - Mongo ma Ndemi)., Tereza Zenklová a kolektiv autorů., and Obsahuje bibliografii
Ants are the most abundant group of soil arthropods in olive groves where they are involved in various trophic relationships of great importance for crops. The system of soil management is one agricultural practice that has a great effect on ants, so the objective of this study was to compare ant populations in organic olive orchards with a ground cover of natural vegetation and others where this natural vegetation is mechanically removed at the beginning of June. Ants were sampled using pitfall traps at 14, 30, 70 and 90 days after the removal of the ground vegetation. Overall, ant biodiversity did not change. However, changes were observed in the abundance of ant species, in particular, in those species that build shallow nests in the soil, both between the rows of trees and under the canopy of olive trees. In contrast, deep nesting species, such as Messor barbarus, were not affected. The response also differed between the various genera: the abundance of Cataglyphis increased, due to there being more of the species C. rosenhaueri, while there was a significant fall in Aphaenogaster, due to the decline in abundance of A. senilis. Thirty days after the removal of vegetation, the response of most of the genera was clearly noticeable, due to the increased activity of workers, and in some cases there were still differences after 90 days. and Mercedes Campos, Luisa Fernández, Francisca Ruano, Belén Cotes, Manuel Cárdenas, Juan Castro.
Among the most extended ecosystems of the temperate zone, the seminatural, dry grasslands constitute a substantial proportion in the Carpathian Basin. The aim of our present study was to investigate the short-term effect of extensive fertilization on the species composition and CO2 exchange of loess grassland at community level. The in situ investigation of the latter parameter have not been yet carried out in Pannonian loess grasslands. Most of the parameters studied showed a considerable interannual variation both in the fertilized and in the control stands. As a result of the treatment, the average species number of the fertilized stand decreased by 22%, which was more significant in the autumn (26%) than in the spring. Diversity values, including Shannon index and species richness, increased by nearly 1.5 times in the year with adequate rainfall compared with the initial values. In general, species richness and the ratio of dicots decreased, while the ratio of therophytes, alien competitors, and C4 plants increased with the addition of fertilizers. Significant carbon sequestration potential was only detected during wet periods in the fertilized grass. The rate of CO2 uptake was found to be nearly five times higher in the fertilized stand and nearly three times higher in the control stand during the wet year compared with the previous, extremely dry year. The CO2 uptake potential of the fertilized grassland exceeded that of the control stand by 12% in the year with high rainfall, while the rate of CO2 exchange dropped by 50% in the dry year in the fertilized stand. Our study reinforced the idea that the decline in species richness was not necessarily followed by the reduction of stand level carbon uptake in a short period due to an insignificant change in ecophysiological functional groups. and S. Z. Czóbel ... [et al.].
Dust deposition on leaf surfaces can impact the growth and physiological traits of plants. We carried out a field experiment to investigate short-term effects of light surface dust on photosynthesis of cotton in the Tarim Basin using chlorophyll fluorescence and gas-exchange techniques. JIP-test analysis of OJIP curves showed that the total performance index for leaves without dust decreased by 32% at noon compared to the morning value. High irradiance at noon reduced actual quantum yield of PSII and increased nonphotochemical quenching for leaves without dust, showing photoinhibition. It suggested that light surface dust alleviated photoinhibition of cotton to high irradiance on a short-term basis. For the leaves without dust, high irradiance induced photoinhibition not only with respect to the photochemistry reactions but the biochemical pathways of CO2 fixation. Mechanisms such as thermal dissipation and enhanced electron flux to PSI protected the photosynthetic apparatus under high irradiance., L. Li, G. Mu., and Obsahuje bibliografii
The Lake Quillwort (Isoëtes lacustris) and Spring Quillwort (I. echinospora) are submerged Lycopods and critically endangered species of Czech flora, each living in a sole lake in the Šumava Mountains (Bohemian Forest). Our 15-year scientific research has been focused on the resistance of these living fossils to the strong acidification of the lakes. Both populations were unable to reproduce for decades and are responding in a quite specific way to the current recovery of the lakes, although this does not quarantee the successful restoration of the quillwort stands. and Martina Čtvrtlíková.
Cuttings of Populus cathayana were exposed to three different alkaline regimes (0, 75, and 150 mM Na2CO3) in a semicontrolled environment. The net photosynthesis rate (PN), mesophyll conductance (gm), the relative limitations posed by stomatal conductance (Ls) and by mesophyll conductance (Lm), photosynthetic nitrogen-use efficiency (PNUE), carbon isotope composition (δ13C), as well as specific leaf area (SLA) were measured. PN decreased due to alkaline stress by an average of 25% and gm decreased by an average of 57%. Alkaline stress caused an increase of Lm but not Ls, with average Ls of 26%, and Lm average of 38% under stress conditions. Our results suggested reduced assimilation rate under alkaline stress through decreased mesophyll conductance in P. cathayana. Moreover, alkaline stress increased significantly δ13C and it drew down CO2 concentration from the substomatal cavities to the sites of carboxylation (Ci-Cc), but decreased PNUE. Furthermore, a relationship was found between PNUE and Ci-Cc. Meanwhile, no correlation was found between δ13C and Ci/Ca, but a strong correlation was proved between δ13C and Cc/Ca, indicating that mesophyll conductance was also influencing the 13C/12C ratio of leaf under alkaline stress. and G. Xu ... [et al.].
Silicon is known to improve resistance against salinity stress in maize crop. This study was conducted to evaluate the influence of silicon application on growth and salt resistance in maize. Seeds of two maize genotypes (salt-sensitive ‘EV 1089’ and salt-tolerant ‘Syngenta 8441’) were grown in pots containing 0 and 2 mM Si with and without 50 mM NaCl. After detailed investigation of ion concentrations in different maize organs, both genotypes were further selected in hydroponic experiment on basis of their contrasting response to salinity stress. In the second experiment, pre-germinated seedlings were transplanted into nutrient solution with 0 and 60 mM NaCl with and without 2 mM Si. Both genotypes differed significantly in their response to salinity. Silicon addition alleviated both osmotic and oxidative stress in maize crop by improving the performance of defensive machinery under salinity stress. Silicon application also improved the water-use efficiency in both tested genotypes under both normal and salinity stress conditions. In conclusion, this study implies that the silicon-treated maize plants had better chance to survive under salinity conditions and their photosynthetic and biochemical apparatus was working far better than that of silicon-non-treated plants., W. U. D. Khan, T. Aziz, M. A. Maqsood, M. Farooq, Y. Abdullah, P. M. A. Ramzani, H. M. Bilal., and Obsahuje bibliografii
Galleria mellonella larvae spin protective tubes, which they use until they finish feeding, when they spin cocoons. A feeding choice experiment showed that some of the silk produced by feeding larvae was consumed in addition to the standard diet (STD). To determine the effect of feeding on silk, last instar larvae were fed for 24 h on foods based on STD but modified by replacing the dry milk component (10% of the diet) with equal amounts of different kinds of silk. While each control larva consumed 21 ± 0.5 mg of the STD and produced 4.5 ± 0.1 mg of silk, larvae that ate the food that contained larval silk consumed 10 ± 0.4 mg of food and produced 6.1 ± 0.1 mg silk; the percentage ratio of silk produced to diet consumed was 21% and 61%, respectively. A more pronounced reduction in food consumption occurred when larvae were supplied with Galleria "cocoon" silk or the sericin fraction of such silk, and only 3.8 mg/larva was ingested of the diet containing Bombyx mori cocoon silk or its sericin fraction. Silk production expressed in terms of percentage of diet consumed was always higher than that recorded for larvae fed STD. We conclude that G. mellonella larvae recycle part of the silk that they produce during feeding. Presence of silk in the diet reduces food intake but increases the ratio of silk production to diet consumption. Sericin fraction of the cocoon silk seems to deter feeding., Haq Abdul Shaik, Archana Mishra, František Sehnal., and Obsahuje bibliografii
Chlorophyll fluorescence serves as a proxy photosynthesis measure under different climatic conditions. The objective of the study was to predict PSII quantum yield using greenhouse microclimate data to monitor plant conditions under various climates. Multilayer leaf model was applied to model fluorescence emission from actinic light-adapted (F') leaves, maximum fluorescence from light-adapted (Fm') leaves, PSII-operating efficiency (Fq'/Fm'), and electron transport rate (ETR). A linear function was used to approximate F' from several measurements under constant and variable light conditions. Model performance was evaluated by comparing the differences between the root mean square error (RMSE) and mean square error (MSE) of observed and predicted values. The model exhibited predictive success for Fq'/Fm' and ETR under different temperature and light conditions with lower RMSE and MSE. However, prediction of F' and Fm' was poor due to a weak relationship under constant (R2 = 0.48) and variable (R2 = 0.35) light., E. Janka, O. Körner, E. Rosenqvist, C.-O. Ottosen., and Obsahuje bibliografii