The effects of NaCl stress on the growth and photosynthetic characters of Ulmus pumila L. seedlings were investigated under sand culture condition. With increasing NaCl concentration, main stem height, branch number, leaf number, and leaf area declined, while Na+ content and the Na+/K+ ratio in both expanded and expanding leaves increased. Na+ content was significantly higher in expanded leaves than in those just expanding. Chlorophyll (Chl) a and Chl b contents declined as NaCl concentration increased. The net photosynthetic rate, intercellular CO2 concentration, stomatal conductance, and transpiration rate also declined, but stomatal limitation value increased as NaCl concentration increased. Both the maximal quantum yield of PSII photochemistry and the effective quantum yield of PSII photochemistry declined as NaCl concentration rose. These results suggest that the accumulation of Na+ in already expanded leaves might reduce damage to the expanding leaves and help U. pumila endure high salinity. The reduced photosynthesis in response to salt stress was mainly caused by stomatal limitation., Z. T. Feng, Y. Q. Deng, H. Fan, Q. J. Sun, N. Sui, B. S. Wang., and Obsahuje bibliografii
The present study was carried out to search whether organophosphate pesticides affect the mechanical properties of the thoracic aorta. Wistar fema le rats (aged 6-8 weeks) were assigned randomly to a control group and groups treated with either dichlorvos or chlorpyriphos for 90 days at a dose of 5 mg/kg/day. After that period, animals were killed and thoracic aorta strips in longitudinal direction were isolated. The stress, strain and elastic modulus were obtained from the strips. Our results showed that chronic administration of chlorpyriphos and dichlorvos caused downward shift of the stress-strain relations compared to the control curve. The elastic modulu s-stress curve revealed distinct characterist ics in the low and high stress regions. A power function was used to simulate the low stress region while a line was fit to the high stress region. Curve fitting procedure illustrated that both pesticides influenced mainly the high stress region, but they had diverse effects at the low stress region. The results also imply that chlorpyriphos and dichlorvos decrease the strength of the aorta and therefore might influence the response of the aorta to mechanical loading induced by blood pressure. and B. Guvenc Tuna ... [et al.].
Salt stress is one of the most critical factors hindering the growth and development of plants. Paclobutrazol (PBZ) is widely used to minimize this problem in agriculture because it can induce salt stress tolerance in plants. This study investigated the effects of PBZ on salt tolerance of seedlings from two Chinese bayberry cultivars (i.e., Wangdao and Shenhong). Plants were treated with three salt concentrations (0, 0.2, and 0.4 % NaCl) and two PBZ concentrations (0 and 2.0 μmol L-1). Application of PBZ increased a relative water content, proline content, chlorophyll (a+b) content, and antioxidant enzyme activities in both cultivars, resulting in a better acclimation to salt stress and an increase in dry matter production. We concluded that PBZ ameliorated the negative effects of salt stress in Chinese bayberry seedlings., Y. Hu, W. Yu, T. Liu, M. Shafi, L. Song, X. Du, X. Huang, Y. Yue, J. Wu., and Obsahuje bibliografii
The effects of postharvest pretreatments on vase life, keeping quality and carbohydrate concentrations in cut sweet pea (Lathyrus odoratus L.) flowers were investigated. Compared to the control, all treatments promoted floret quality and extended longevity. The cut flowers held in the solution containing sucrose + 8-hydroxyquinoline (Suc+HQS) was more effective in promoting absorption rate, achieved greater maximum fresh mass, had better water balance for a longer period, extended the vase life (up to 17 d), and delayed degradation of chlorophylls. The same treatment also enhanced the concentration of soluble carbohydrates in the petals and stems and leaf chlorophyll (Chl) content, whereas it was lowest in silver thiosulphate (STS) treatment. However, concentrations of anthocyanin in the petals were higher for treatment with sucrose or STS plus sucrose than in control or STS alone treatments. Our results suggest that pulse treatment with HQS plus sucrose for 12 h is the most effective for improving pigmentation and use as a commercial cut flower preservative solution to delay flower senescence, enhance quality, and prolong the vase life of sweet pea. The results also showed that soluble carbohydrate concentration in petals and stems is an important factor in determining the vase life of sweet pea flowers., K. M. Elhindi., and Obsahuje bibliografii
The invasion of Spartina alterniflora along the coasts of China has allowed this C4 grass to outcompete often much of the native, salt marsh vegetation, such as Phragmites australis (C3 grass), in the Yangtze Estuary. In this study, native grass, P. australis, and
non-native grass, S. alterniflora, were grown in fresh and saline water (moderate salinity of 15‰ and high salinity of 30‰) to compare the effects of salinity on photosynthetic and biochemical parameters in combination with measurement temperatures. The C4 grass, S. alterniflora, showed a greater CO2 assimilation rate than P. australis, across the tested temperatures. The net photosynthetic rate declined significantly with increasing salinity as a result of inhibited stomatal conductance together with a greater decrease in the maximum rate of electron transport (Jmax). In P. australis, salt treatments shifted the optimum temperatures for the maximum rate of carboxylation by Rubisco (Vcmax) and J max to lower temperatures. S. alterniflora showed a greater salt tolerance to moderate stress than that of the native grass, with lower sensitivity of V cmax, Jmax, and the maximum rate of phosphoenolpyruvate carboxylation. Both moderate and high stress decreased significantly stomatal conductance of S. alterniflora; high salinity reduced significantly photosynthetic efficiency and Jmax. Our findings indicated that the combination of stomatal conductance, enzyme activity, and electron transport affected the photosynthetic performance of the plants in response to salt treatments. The success of S. alterniflora could be probably attributed to its C4 photosynthetic pathway and the tolerance to moderate salinity. In this study, a modified parameterization of the photosynthetic model was suggested to support a more reasonable simulation of photosynthesis under salt stress., Z.-M. Ge, L.-Q. Zhang, L. Yuan, C. Zhang., and Obsahuje bibliografii
The effects of NaCl treatment were analysed in two species of considerably different resistance. In glycophyte, the content of ascorbate decreased but lipophilic antioxidants (α-tocopherol, plastochromanol, and hydroxy-plastochromanol) increased due to 150 mM NaCl. In halophyte, 300 mM NaCl caused a significant increase in hydrophilic antioxidants (ascorbate, total glutathione) but not in the lipophilic antioxidants. The redox states of plastoquinone (PQ) and P700 were also differently modulated by salinity in both species, as illustrated by an increased oxidation of these components in glycophyte. The presented data suggest that E. salsugineum was able to avoid a harmful singlet oxygen production at PSII, which might be, at least in part, attributed to the induction of the ascorbate-glutathione cycle. Another important cue of a high salinity resistance of this species might be the ability to sustain a highly reduced states of PQ pool and P700 under stress, which however, drastically affect the NADPH yield., M. Wiciarz, E. Niewiadomska, J. Kruk., and Obsahuje bibliografii
An important mechanism underlying cochlear hair cell (HC) susceptibility to hypoxia/ischemia is the influx of Ca2+. Two main ATP-dependent mechanisms contribute to maintaining low Ca2+ levels: uptake of Ca2+ into intracellular stores via smooth endoplasmic reticulum calcium ATPase (SERCA) and extrusion of Ca2+ via plasma membrane calcium ATPase (PMCA). The effects of the SERCA inhibitors thapsigargin (10 nM-10 μM) and cyclopiazonic acid (CPA; 10-50 μM) and of the PMCA blockers eosin (1.5-10 μM) and o-vanadate (1-5 mM) on inner and outer hair cells (IHCs/OHCs) were examined in normoxia and ischemia using an in vitro model of the newborn rat cochlea. Exposure of the cultures to ischemia resulted in a significant loss of HCs. Thapsigargin and CPA had no effect. Eosin decreased the numbers of IHCs and OHCs by up to 25 % in normoxia and significantly aggravated the ischemia-induced damage to IHCs at 5 and 10 μM and to OHCs at 10 μM. o-Vanadate had no effect on IHC and OHC counts in normoxia, but aggravated the ischemia-induced HC loss in a dose-dependent manner. The effects of eosin and o-vanadate indicate that PMCA has an important role to play in protecting the HCs from ischemic cell death., N. Amarjargal, B. Mazurek, H. Haupt, N. Andeeva, J. Fuchs, J. Gross., and Obsahuje bibliografii a bibliografické odkazy
The effects of shoot girdling on stomatal conductance (gs), leaf photosynthesis (PN), concentrations of carbohydrates, nitrogen and chlorophyll (Chl) in leaves, areal leaf mass (ALM), the diameter and length of shoots, and bud abscission in pistachio were investigated. Girdling individual shoots at the base of the current year’s shoot (girdle I), separating inflorescent buds on the terminal current year’s shoot from the developing fruits on the previous year’s shoot, reduced inflorescent bud abscission by 70% in comparison to nongirdled controls. Girdle I significantly reduced concentrations of nitrogen in leaves but increased those of nonstructural carbohydrates particularly of starch. Shoot diameter increased by 13.1% and 26.4% at 33 and 81 days after girdling (DAG), respectively, compared to 1% and 3.4% in the control, respectively. Both the leaf dry mass/fresh mass ratio and ALM were increased significantly by girdle I from 12 DAG. The concentrations of Chl a, Chl b, Chl (a+b), as well as the ratio of Chl a/b, all decreased with girdle I. The greatest negative effect of girdle I was on gs and PN. PN was reduced by 55% of its initial value and was 44% less than in the control leaves at 10 DAG, and fell to approximately 30% that of the control from 21 DAG. In contrast, girdling at the base of one-year-old shoots (girdle II), thus not separating fruits from the inflorescent buds, did not significantly affect gs or PN. The effect of girdling on PN and the possible factors that are involved in the reduction of photosynthesis in pistachio are discussed., S. N. Vemmos, A. Papagiannopoulou, S. Coward., and Obsahuje bibliografii
a1_We investigated the influence of salinity (0, 25, 50, or 75 mM NaCl) on gas exchange and physiological characteristics of nine citrus rootstocks (Cleopatra mandarin, Carrizo citrange, Macrophylla, Iranian mandarin Bakraii, Rangpur lime, Rough lemon, Sour orange, Swingle citrumelo, and Trifoliate orange) in a greenhouse experiment. Total plant dry mass, total chlorophyll (Chl) content, and gas-exchange variables, such as net photosynthetic rate (PN), stomatal conductance (g s), intercellular CO2 concentration, were negatively affected by salinity. In addition, ion concentrations of Cl- and Na+ increased by salinity treatments. Salinity also increased Mg2+ content in roots and reduced Ca2+ and Mg2+ concentrations in leaves. The K+ concentration in leaves was enhanced at low salinity (25 mM NaCl), whereas it decreased with increasing salinity stress. Salinity caused a decline in K+ contents in roots., a2_The rootstocks showed major differences in the extent of Cl- and Na+ accumulation in leaves and in their ability to maintain the internal concentrations of essential nutrients in response to different salinity. Therefore, in addition to inhibitory effects of high concentrations of Cl- and Na+, an imbalance of essential nutrients may also contribute to the reduction in gas exchange under saline conditions. Higher tolerance of rootstocks to salinity could be associated with the reduction of Cl- and Na+ uptake and transport to leaves, ability to keep higher Chl, gs, PN, and better maintenance of nutrient uptake even under high salinity. We found that Sour orange and Cleopatra mandarin were the rootstocks most tolerant to salinity of all nine studied. In addition, Trifoliate orange, Carrizo citrange, and Swingle citrumelo were the rootstocks most sensitive to salt stress followed by the Rough lemon and Macrophylla that showed a low-to-moderate tolerance, and Rangpur lime and Bakraii, with a moderate-to-high tolerance to high salinity., D. Khoshbakht, A.A. Ramin, B. Baninasab., and Obsahuje bibliografii
This study investigated the effect of solar ultraviolet radiation (UVR) and temperature on a chain length and photosynthetic performance of diatom Chaetorceros curvisetus. The cells were cultured in large quartz tubes and exposed to PAR, PAR + UV-A (PA), or PAR + UV-A + UV-B (PAB) radiation at 20°C and 28°C for six days, respectively. After recovery for 1 h, the cells were exposed again to three different radiations for 1 h. Then, a change in the photochemical efficiency (FPSII) was examined and UVR-induced photoinhibition was calculated. The percentage of long chains (more than five single cells per chain) in C. curvisetus significantly increased from 8.2% (PAR) to 38.9% (PAB) at 20°C; while it was not notably affected at 28°C. Mycosporine-like amino acids (MAAs) concentration obviously increased by irradiance increment from PAR to PAB at 20°C. Chlorophyll (Chl) a concentration significantly declined with increasing irradiance at 20°C. Both MAAs and Chl a concentrations were not obviously changed by irradiance at 28°C. Before and after reexposure, FPSII was significantly reduced both at 20°C and 28°C. UVR-induced photoinhibition at 20°C (39%) was higher than that at 28°C (30.9%). Solar UV radiation, especially UV-B, could significantly influence the percentage of long chains of C. curvisetus, especially at low temperature. UVR-induced photoinhibition can be alleviated by higher temperatures., W. Guan, X. Peng, S. Lu., and Obsahuje seznam literatury