The seedlings of wheat were treated by salt-stress (SS, molar ratio of NaCl: Na2SO4 = 1:1) and alkali-stress (AS, molar ratio of NaHCO3: Na2CO3 = 1:1). Relative growth rate (RGR), leaf area, and water content decreased with increasing salinity, and the extents of the reduction under AS were greater than those under SS. The contents of photosynthetic pigments did not decrease under SS, but increased at low salinity. On the contrary, the contents of photosynthetic pigments decreased sharply under AS with increasing salinity. Under SS, the changes of net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were similar and all varied in a single-peak curve with increasing salinity, and they were lower than those of control only at salinity over 150 mM. Under AS, PN, gs, and E decreased sharply with rising salinity. The decrease of gs might cause the obvious decreases of E and intercellular CO2 concentration, and the increase of water use efficiency under both stresses. The Na+ content and Na+/K+ ratio in shoot increased and the K+ content in shoot decreased under both stresses, and the changing extents under AS were greater than those under SS. Thus SS and AS are two distinctive stresses with different characters; the destructive effects of AS on the growth and photosynthesis of wheat are more severe than those under SS. High pH is the key feature of the AS that is different from SS. The buffer capacity is essentially the measure of high pH action on plant. The deposition of mineral elements and the intracellular unbalance of Na+ and K+ caused by the high pH at AS might be the reason of the decrease of PN and gs and of the destruction of photosynthetic pigments. and C. W. Yang ... [et al.].
P-wave velocity anisotropy of rocks is often investigated by laboratory methods. The extrapolation of the laboratory results to larger rock units requires comparison with direct field measurements. Physical properties of deep-originated rocks were performed on mantle-derived peridotite from the Ivrea zone (N orthwestern Italy). These rock s were exhumed by tectonic processes during collision orogeny up to the Earth’s surface. The direct surface seismic measurements of elastic waves velocity were realized by means of shallow seismic refraction method on the outcrop of peridotite. The measuring base was about 10 m long. Laboratory seismic anisotropy measurement was realized on rock samples from the same outcrop. The geographically oriented spherical samples with diameter 50 mm were radiated by elastic waves in 132 directions under confining stress from atmospheric level up to 200 MPa. Laboratory and field values of the anisotropy of seismic wave ve locities were compared and different scales of measurements were evaluated. The field measuremen ts used frequency about 1 kHz whereas the laboratory measur ement used 700 kHz radiation. Field measurements proved relatively high value of anisotropy P-wave propagation - 25%, while laboratory experiments only 1.5%. This difference is caused by different reason of anisotropy. Laboratory samples contain only microcraks, which represents nearly continuum with rega rd to ultrasound wave length (11 mm). Rock massif, however, contains beside mickrocraks also cracks with comparable size of applied seismic wave length (10 m)., Jan Vilhelm, Vladimír Rudajev, Roman Živor, Tomáš Lokajíček and Zdeněk Pros., and Obsahuje bibliografické odkazy
The effects of potassium (K) deficiency on chlorophyll (Chl) content, photosynthetic gas exchange, and photosystem II (PSII) photochemistry during the seedling stage were investigated in two soybean [Glycine max (L.) Merr.] cultivars, low-K sensitive Tiefeng31 and low-K tolerant Shennong6. The cultivars were grown hydroponically in K-sufficient (KS) and K-deficient (KD) solutions. Photosynthetic gas exchange and Chl content in Tiefeng31 were severely affected by the low K condition, but were almost unaffected in Shennong6. This difference is in accordance with the PSII photochemistry in the plants, indicating that the photosynthetic apparatus of Shennong6 is more tolerant to low-K stress than that of Tiefeng31. and X.-T. Li ... [et al.].
This paper discusses the quality of slant wet delays (SWD) computed from GPS measurements. The SWDs are generally used as input data for GPS tomography, which allows the three-dimensional reconstruction of water vapour distribution in the atmosphere. The research presented is based on a comparison of slant wet delays acquired by different strategies based on double-differenced Global Positioning System (GPS) data. The GPS-derived SWDs were compared with those directly measured by a water vapour radiometer (W VR). The best results from the applied G PS strategies were achieved by a simple mapping of GPS-derived zenith total delays into SWD without adding horizontal gradients or post-fit residuals., Michal Kačmařík, Jan Douša and Jan Zapletal., and Obsahuje bibliografické odkazy
Sandstones have been widely used as a building material since the medieval time all around the Europe. Porosity is one of the main factors affecting the resistance to weathering processes and consequently to the changes of mechanical and physical properties of these stones. Rock material is generally negatively influenced especially during the winter period when frost action takes place. Effect of salt crystals and ice formation depends on the character of pore space, including the pore size distribution. Mercury porosimetry is well known method which provides information about porosity and pore size distribution of samples, but as any other method, it has its own limitations. X-ray microtomography can be used as a complementary method enabling another "view" into the pore space. Main aim of this paper has been to provide the information about the use of these two mentioned methods and comparison of obtained results, within the study of sandstone weathering. The research was focused on two commonly used Czech Cretaceous sandstones - Hořice and Božanov. The stones were exposed to the accelerated durability test which is based on the meteorological data measured in Prague winters from 1998 to 2008. There were described the changes in the area of pores diameters > 5 μm. Use of mercury porosimetry together with X-ray microtomgraphy enabled more detailed understanding of the processes inside the stone structure., Kateřina Kovářová, Robert Ševčík and Zuzana Weishauptová., and Obsahuje bibliografické odkazy
The rare and endangered plant, Begonia fimbristipula, shows red and green phenotypes, differentiated by a coloration of the abaxial leaf surface. In this study, we compared morphological and physiological traits of both phenotypes. The results showed that the red phenotype contained a significantly higher chlorophyll content, closer arrangement of chloroplasts, and a more developed grana. In addition, the red phenotype transferred significantly more light energy into the electron transport during the photoreaction. Similarly, the maximum photosynthetic rate, instantaneous water-use and light-use efficiencies of the red B. fimbristipula were all significantly higher than those of the green individuals. The differentiation between these two phenotypes could be caused by their different survival strategies under the same conditions; epigenetic variations may be in some correlation with this kind of phenotype plasticity. Red B. fimbristipula has an advantage in resource acquisition and utilization and possesses a better self-protection mechanism against changes in environmental conditions, therefore, it might adapt better to global climate change compared to the green phenotype. Further studies on the possible epigenetic regulation of those phenotypic differentiations are needed., Y. Wang, L. Shao, J. Wang, H. Ren, H. Liu, Q. M. Zhang, Q. F. Guo, X. W. Chen., and Seznam literatury
The purpose of the present study was to examine whether the level of oxygen uptake (V.o2) at the onset of decrement-load exercise (DLE) is lower than that at the onset of constant-load exercise (CLE), since power output, which is the target of V.o2 response, is decreased in DLE. CLE and DLE were performed under the conditions of moderate and heavy exercise intensities. Before and after these main exercises, previous exercise and post exercise were performed at 20 watts. DEL was started at the same power output as that for CLE and power output was decreased at a rate of 15 watts per min. V.o2 in moderate CLE increased at a fast rate and showed a steady state, while V.o2 in moderate DLE increased and decreased linearly. V.o2 at the increasing phase in DLE was at the same level as that in moderate CLE. V.o2 immediately after moderate DLE was higher than that in the previous exercise by 98±77.5 ml/min. V.o2 in heavy CLE increased rapidly at first and then slowly increased, while V.o2 in heavy DLE increased rapidly, showing a temporal convexity change, and decreased linearly. V.o2 at the increasing phase of heavy DLE was the same level as that in heavy CLE. V.o2 immediately after heavy DLE was significantly higher than that in the previous exercise by 156±131.8 ml/min. Thus, despite the different modes of exercise, V.o2 at the increasing phase in DLE was at the same level as that in CLE due to the effect of the oxygen debt expressed by the higher level of V.o2 at the end of DLE than that in the previous exercise., T. Yano, H. Ogata, R. Matsuura, T. Arimitsu, T. Yunoki., and Obsahuje bibliografii a bibliografické odkazy
The parameters estimated from traditional A/Ci curve analysis are dependent upon some underlying assumptions that substomatal CO2 concentration (Ci) equals the chloroplast CO2 concentration (Cc) and the Ci value at which the A/Ci curve switches between Rubisco- and electron transport-limited portions of the curve (Ci-t) is set to a constant. However, the assumptions reduced the accuracy of parameter estimation significantly without taking the influence of Ci-t value and mesophyll conductance (gm) on parameters into account. Based on the analysis of Larix gmelinii's A/Ci curves, it showed the Ci-t value varied significantly, ranging from 24 Pa to 72 Pa and averaging 38 Pa. t-test demonstrated there were significant differences in parameters respectively estimated from A/Ci and A/Cc curve analysis (p<0.01). Compared with the maximum ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate (Vcmax), the maximum electron transport rate (Jmax) and Jmax/Vcmax estimated from A/Cc curve analysis which considers the effects of gm limit and simultaneously fits parameters with the whole A/Cc curve, mean Vcmax estimated from A/Ci curve analysis (Vcmax-Ci) was underestimated by 37.49%; mean Jmax estimated from A/Ci curve analysis (Jmax-Ci) was overestimated by 17.8% and (Jmax-Ci)/(Vcmax-Ci) was overestimated by 24.2%. However, there was a significant linear relationship between Vcmax estimated from A/Ci curve analysis and Vcmax estimated from A/Cc curve analysis, so was it Jmax (p<0.05). and W. Zeng ... [et al.].
a1_Photosynthetic gas exchange, dry mass production, water relations and inducibility of crassulacean acid metabolism (CAM) pathway as well as antioxidative protection during the C3-CAM shift were investigated in Sedum album and Sedum stoloniferum from Crassulaceae under water stress for 20 days. Leaf relative water content (RWC), leaf osmotic and water potential decreased with increasing water stress in both studied species. Significant reduction in dry matter production and leaf thickness was detected only in S. stoloniferum after 20-d water stress. Δtitratable acidity and phosphoenolpyruvate carboxylase (PEPC) activity in S. album responded to drought at early stages of stress treatment, continued to increase throughout the entire stress period and reached levels 15 times higher than those in well-watered plants. In S. stoloniferum, however, both parameters responded later and after a transient increase declined again. In S. stoloniferum, in spite of increase by drought stress, net night-time CO2 assimilation was negative resembling a C3-like pattern of gas exchange. Catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) activities increased in plants subjected to mild water stress while declined as the stress became severe. Although malondialdehyde (MDA) content was higher in drought-stressed S. stoloniferum, the increase in the concentration of hydrogen peroxide (H2O2) that may act as a signal for C3-CAM transition was higher in S. album compared with S. stoloniferum. In drought-stressed plants, SOD activity showed a clear diurnal fluctuation that was more steadily expressed in S. album. In addition, such pattern was observed for CAT only in S. album. We concluded that temporal and diurnal fluctuation patterns in the activity of antioxidant enzymes depended on duration of drought stress and was related to the mode of photosynthesis and degree of CAM induction., a2_According to our results, S. stoloniferum developed a low degree of CAM activity, e.g. CAM-cycling metabolism, under drought conditions., G. Habibi, R. Hajiboland., and Obsahuje bibliografii
Orychophragmus violaceus, Brassica campestris cv. Chuanyou No.8, and Brassica juncea cv. Luzhousileng diurnal changes of net photosynthetic rate (PN) and activities of carbonic anhydrase (CA) of leaves were studied. One uni-modal curve occurred at the diurnal changes of PN in O. violaceus, but bimodal curves were found in B. campestris and B. juncea. Thus photosynthetic midday depression was not found in O. violaceus but in both Brassica species. Midday depression of PN in O. violaceus was not related to high temperature or low humidity at midday but to the activity of CA. and Y. Y. Wu ... [et al.].