This study compared the effects of salt (NaCl) stress on growth, photosynthesis and solute accumulation in seedlings of the three poplar (Populus bonatii) cultivars Populus × BaiLin-2 (BL-2), Populus × BaiLin-3 (BL-3), and Populus × Xjiajiali (XJJL). The results showed that BL-2 and BL-3 could not survive at a salinity level of 200 mM but XJJL grew well. The effect of moderate salt stress on leaf extension of the three cultivars was only slight. At a high level of salinity, however, NaCl clearly inhibited leaf extension of BL-2 and BL-3, whereas it did not affect that of XJJL, and the net photosynthetic rate (PN) in XJJL was much higher than those of BL-2 and BL-3. The lower PN of BL-2 and BL-3 might be associated with the high concentration of Na+ and/or Cl- accumulated in the leaves, which could be toxic in photosynthesis system. In summary, the greater salt-tolerance of XJJL compared with that of BL-2 and BL-3 might be explained by the higher PN and photosynthetic area, the lower Na+/K- ratio and Cl- in the leaf, and the greater accumulation of soluble sugars and SO4 2-. and W. Chen ... [et al.].
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
The effect of four different NaCl concentrations (from 0 to 102 mM NaCl) on seedlings leaves of two corn (Zea mays L.) varieties (Aristo and Arper) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthesis, stomatal conductance, photosynthetic pigments concentration, tissue hydration and ionic accumulation. Salinity treatments showed a decrease in maximal efficiency of PSII photochemistry (Fv/Fm) in dark-adapted leaves. Moreover, the actual PSII efficiency (ϕPSII), photochemical quenching coefficient (qp), proportion of PSII centers effectively reoxidized, and the fraction of light used in PSII photochemistry (%P) were also dropped with increasing salinity in light-adapted leaves. Reductions in these parameters were greater in Aristo than in Arper. The tissue hydration decreased in salt-treated leaves as did the photosynthesis, stomatal conductance (g s) and photosynthetic pigments concentration essentially at 68 and 102 mM NaCl. In both varieties the reduction of photosynthesis was mainly due to stomatal closure and partially to PSII photoinhibition. The differences between the two varieties indicate that Aristo was more susceptible to salt-stress damage than Arper which revealed a moderate regulation of the leaf ionic accumulation. and H. Hichem, A. El Naceur, D. Mounir.
Six-year-old Scots pine (Pinus sylvestris L.) seedlings were grown in open top chambers (OTCs) at ambient (AC) or elevated (ambient + 400 µmol mol-1; EC) CO2 concentration for three years (1996-1998). Chlorophyll (Chl) a fluorescence of current and one-year-old needles was measured in the field at two-weekly intervals in the period July-October 1998. In addition, Chl, carbon (C), and nitrogen (N) concentrations in both needle age classes were determined monthly during the same period. Chl fluorescence parameters were not significantly affected by EC, suggesting there was no response of the light reactions and the photochemical efficiency of photosystem 2. Chl concentrations were not significantly different but a reduced N concentration was observed in needles of EC treatment. Significant differences between needle age classes were observed for all parameters, but were most apparent under EC and toward the end of the growing season, possibly due to an acclimation process. As a result, significant interactions between CO2 treatment, needle age class, and season were found. This study emphasizes the importance of repeated measures including different leaf/needle age classes to assess the photosynthetic response of trees under EC. and B. Gielen, M. E. Jach, R. Ceulemans.
Plant essential oils (EOs) have been reported to have health benefit properties and their preventive and therapeutic use in animals is expected to increase in the future. We evaluated the influence of five essential oils obtained from plant species which are known to have positive antimicrobial, antioxidative and anti-inflammatory effects – sage EO from Salvia officinalis L. (Lamiaceae), oregano EO from Origanum vulgare L. (Lamiaceae), thyme EO from Thymus vulgaris L. (Lamiaceae), clove EO from Syzygium aromaticum L. (Myrtaceae) and cinnamon EO from Cinnamomum zeylanicum Blume (Lauraceae) on the growth and development of mouse preimplantation embryos in vivo. Essential oils were added to commercial diet at concentrations of 0.25 % for sage EO, thyme EO, clove EO, cinnamon EO and 0.1 % for oregano EO, and fed to ICR female mice for 2 weeks ad libitum. Females were then mated with males of the same strain. Embryos obtained on Day 4 of pregnancy at the blastocyst stage were stained by morphological triple staining (Hoechst, PI, Calcein-AM) and evaluated using fluorescent microscopy. The effects of essential oils were estimated by the viability of embryos, number of nuclei and distribution of embryos according to nucleus number. Cinnamon EO significantly decreased the number of nuclei and the distribution of embryos according to nucleus number was significantly altered. Sage EO negatively influenced the distribution of embryos according to nucleus number. Clove and oregano EOs induced a significantly increased rate of cell death. Only thyme EO had no detectable effects on embryo development. In conclusion, none of the essential oils had any positive effect on embryo development, but some of them reduced the number of cells and increased the incidence of cell death., M. Domaracký, P. Rehák, Š. Juhás, J. Koppel., and Obsahuje bibliografii a bibliografické odkazy
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
The effects of simulated acid rain on gas exchange, chlorophyll fluorescence, and anti-oxidative enzyme activity in cucumber seedlings (Cucumis sativus L. cv. Jingchun No. 4) were investigated. Acid rain significantly reduced net photosynthetic rate and mainly non-stomatal factors contributed to the decrease of photosynthesis during the experimental period. The reduced photosynthesis was associated with a decreased maximal photochemical efficiency (Fv/Fm) and the average quantum yield of the photosystem 2 (PS2) reaction centres (ΦPS2). Meanwhile, acid rain significantly increased the activities of guaiacol peroxidase (GPX) and superoxide dismutase (SOD), but decreased the activity of catalase (CAT) together with an increased content of malonyldialdehyde (MDA), Hence the changes in photosynthesis in acid rain treatment might be a secondary effect of acidity damage probably due to lipid peroxidation of lipids and proteins in thylakoid membrane rather than direct effect on PS2 reaction centre. and Jing-Quan Yu, Su-Feng Ye, Li-Feng Huang.
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
The combined effects of water status, vapour pressure deficit (VPD), and elevated temperature from heading to maturity were studied in barley. Plants growing at high VPD, either under well-watered or water deficit conditions, had higher grain yield and grain filling rate than plants growing at low VPD. By contrast, water stress decreased grain yield and individual grain dry matter at any VPD. Water regime and to a lesser extent VPD affected δ13C of plant parts sampled at mid-grain filling and maturity. The differences between treatments were maximal in mature grains, where high VPD increased δ13C for both water regimes. However, the total amount of water used by the plant during grain filling did not change as response to a higher VPD whereas transpiration efficiency (TE) decreased. The net photosynthetic rate (PN) of the flag leaves decreased significantly under water stress at both VPD regimes. However, PN of the ears was higher at high VPD than at low VPD, and did not decrease as response to water stress. The higher correlation of grain yield with PN of the ear compared with that of the flag leaf support the role of ear as the main photosynthetic organ during grain filling under water deficit and high VPD. The deleterious effects of combined moderately high temperature and drought on yield were attenuated at high VPD. and M. Sánchez-Díaz ... [et al.].