This study was conducted to assess whether silicon (Si) supply can alleviate the harmful effects of severe salinity in barley (Hordeum vulgare). Plants were grown on non-saline (0 mM NaCl) or saline (200 mM NaCl) nutrient media supplemented or not with 0.5 mM Si. Salinity impacted plant morphology and induced sodium and chloride accumulation within plant tissues. It significantly affected almost all measured parameters. Interestingly, Si supply alleviated salt stress effects on plant morphology, growth (up to +59%), water status (up to +74%), membrane integrity (up to +35%), pigment contents (up to +121%), and the activity of the two photosystems (PSI and PSII) by improving their yields, and by reducing their energy dissipation. Si beneficial effect was more pronounced on PSI as compared to PSII. As a whole, data inferred from the present study further confirmed that silicon application is an effective approach to cope with salinity.
Employing the non-invasive techniques of infra-red gas analysis and pulse amplitude modulated chlorophyll fluorometry, we determined the partitioning of photosynthetic electrons between photosynthetic carbon reduction and other reductive processes resulting in the formation of active oxygen species (AOS) in intact green leaves. This we studied in plant species that are adapted to two different agro-climatic conditions, namely the warm plains (76°36'E, 9°32'N) and the cool mountains (1 600 m a.s.l.) in the south Indian state of Kerala. Ground frost and low temperature were more harmful to those species adapted to the warm plains than the ones adapted to the cool mountains. Exposure to low temperature decreased leaf photosynthetic carbon assimilation rates and quantum yield of photochemical activity in species naturally adapted to the warm plains. High irradiances further aggravated the harmful effects of low temperature stress possibly by overproducing AOS. This resulted in severe peroxidative damage as inferred by the accumulation of malondialdehyde (MDA) in the leaves. and B. Alam, J. Jacob.
Malondialdehyde (MDA), Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and selenium-dependent glutathione peroxidase (GSPHx) are currently considered to be basic markers of oxidative stress. MDA is one of the end-products of the peroxidation of membrane lipids, whereas enzymes Cu,Zn-SOD and GSHPx belong to the natural antioxidants. The role of oxygen free radicals in the pathogenesis of many diseases is well documented. The aim of this study was to ascertain the influence of insulin-induced acute hypoglycemia on oxidative stress in the brain tissue. Hypoglycemia was induced in ICR mice by intraperitoneal administration of insulin at a dose 24 IU/kg. There was a correlation between the severity of hypoglycemia and the levels of MDA, Cu,Zn-SOD and GSHPx. The results showed that in severe hypoglycemia (serum glucose concentration below 1.0 mmol/l) the lipoperoxidation in brain tissue expressed as the level of MDA was higher in comparison with normoglycemic controls (glycemia around 3.7 mmol/l) as well as in comparison with the levels of MDA during moderate hypoglycemia (glycemia ranging between 1-2 mmol/l). This indicates the enhancement of lipoperoxidation in the brain tissue during severe hypoglycemia. However, both enzymes - Cu,Zn-SOD or GSHPx - did not show a similar tendency., J. Patočková, P. Marhol, E. Tůmová, M. Kršiak, R. Rokyta, S. Štípek, J. Crkovská, M. Anděl., and Obsahuje bibliografii
We investigated the physiological effect of night chilling (CN) on potted seedlings of two tropical tree species, Calophyllum polyanthum and Linociera insignis, in Xishuangbanna, southwest China. Seedlings grown under 8, 25, and 50 % daylight for five months were moved to a 4-6 °C cold storage house for three consecutive nights, and returned to the original shaded sites during the day. CN resulted in strong suppression of photosynthesis and stomatal conductance for L. insignis, and reduced photorespiration rates, carboxylation efficiency, and maximum photochemical efficiency of photosystem 2 (PS2) at dawn and midday for both species. CN increased dawn and midday rates of non-photochemical quenching, and the contents of malondialdehyde and H2O2 for both species. CN also induced inactivation or destruction of PS2 reaction centres. The impacts of CN on tropical seedlings increased with the number of CN. Shading could significantly mitigate the adverse effects of CN for both species. After 3-d-recovery, gas exchange and fluorescence parameters for both species returned to pre-treatment levels in most cases. Thus CN induced mainly stomatal limitation of photosynthesis for L. insignis, and non-stomatal limitation for C. polyanthum. C. polyanthum was more susceptible to CN than L. insignis. Fog, which often occurs in Xishuangbanna, could be beneficial to chilling sensitive tropical seedlings in this area through alleviating photoinhibition or photodamage by reducing sunlight. and Y.-L. Feng, K.-F. Cao.
In view of predicted climatic changes for the Mediterranean region, study of high temperature and drought impacts on physiological responses of endangered species regains relevance. In this context, micropropagated plants of Tuberaria major, a critically endangered species, endemic of Algarve, were transferred to a controlled-environment cabinet with day/night temperatures set at 25/18°C (Reference) or 32/21°C (HT). After 15 days of HT acclimation, some plants were subjected to progressive drought followed by rewatering. The enhancement of temperature alone did not affect water relations and photosynthetic rates (PN) but the stomatal conductance (gs) exhibited a 3-fold increase in comparison with reference plants. The maximum quantum yield of photosystem (PS) II (Fv/Fm), the effective quantum yield of PSII photochemistry (ΦPSII), carotenoid (Car) and anthocyanin content enhanced, whereas the quantum yields of regulated (ΦNPQ) and nonregulated (ΦNO) energy dissipation decreased. Drought combined with HT reduced predawn leaf water potential to values of about -1.3 MPa, which had adverse effects on gas exchange and PSII activity. Values of PN and gs were 71 and 79% lower than those of HT plants. An impairment of photochemical activity was also observed: the decrease in ΦPSII and the increase of ΦNPQ. However, an irreversible photoinhibitory damage had not occurred. Carotenoid and anthocyanin content remained elevated and soluble sugars (SS) increased twice, whereas proline and MDA accumulation was not detected. On the first 24 h after water-stress relief, gs, PN, ΦPSII, and ΦNPQ did not recover, but SS returned to the reference level. Overall, T. major acquired an adequate capacity for a protection against the development of oxidative stress during drought and water recovery under HT. These findings suggest that T. major is prepared to deal with predicted climate changes., M. L. Osório, J. Osório, A. Romano., and Obsahuje bibliografii
Drought stress triggered the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2) both in non-Bt and Bt cotton with simultaneous production of antioxidant enzymes. And there was no significant difference between non-Bt and Bt cotton under drought stress. In contrast to this, we observed a significant reduction of Bt toxin proteins under 72 h of drought stress in Bt cotton. and P. Parimala, K. Muthuchelian
The aim of our study was to answer whether any positive correlation exists between K+ uptake and salt tolerance in wheat. We carried out a sand-culture experiment with salt-tolerant, DK961 (ST), and salt-sensitive, JN17 (SS), wheat cultivars, where photosynthesis, the K+/Na+ ratio, growth, and the biomass yield were examined. The seeds were exposed for four weeks to six NaCl concentrations (50, 100, 150, 200, 250, and 300 mM), which were embodied in the Hoagland solution. Salinity-induced decrease of K+ or increase in the Na+ content was much smaller in ST than that in SS. The reductions in the light-saturated photosynthetic rate (P Nmax) and chlorophyll content caused by salinity were smaller in the ST compared to SS. Stomatal conductance decreased in both cultivars under saline conditions; nevertheless, it was lower in SS than in ST. The antioxidative capacity was higher in ST than that in SS under saline conditions. Significant positive correlations were observed in both cultivars between K+ contents and P Nmax/biomass yields. We suggest that higher-affinity K+ uptake might play a key role in higher salt tolerance and it might be a reliable indicator for breeding new species of salt-tolerant wheat., D. Cheng, G. Wu, Y. Zheng., and Obsahuje seznam literatury
In this study, the JIP test was used to assess the drought tolerance of two sweet cherry cultivars (Prunus avium L.) (modern and autochthonous). Plants were exposed to progressive drought by withholding water and their fast (< 1 s) chlorophyll fluorescence kinetics was evaluated. JIP test analysis showed that drought stress caused a greater decrease in performance indices (PIABS and PItotal) in a modern cultivar, as compared to an autochthonous one. Our results suggest that limited reoxidation of primary quinone electron acceptor (QA), higher amount of secondary quinone electron acceptor (QB-) nonreducing reaction centres, or inhibition of the electron transport between QA and QB, decreased more seriously the photosynthetic performance of the modern cultivar. Further, higher positive L- and K-bands observed for the modern cultivar also suggest lower energetic connectivity between PSII units and increased inhibition of oxygen-evolving complex over autochthonous cultivar. Our results suggest that the autochthonous cultivar Crveni hrušt had better photosynthetic performance under drought conditions, compared to the modern cultivar New Star.
Low temperature during the vegetative stage affects rice (Oryza sativa L.) seed-setting rate in Heilongjiang province at Northeast China. However, little is known about changes of the photosynthetic rate and physiological response in contrasting rice cultivars during chilling periods. In this study, two rice cultivars with different chilling tolerance were treated with 15°C from June 27 to July 7. The chilling-susceptive cultivar, Longjing11 (LJ11), showed a significant decrease in a ripening rate and seed-setting rate after being treated for four days, whilst chilling-tolerant cultivar, Kongyu131 (KY131), was only slightly affected after 4-d treatment. The photosynthetic activities, chlorophyll contents, and antioxidative enzyme activities in LJ11 decreased significantly along with the chilling treatment. The decrease in ß-carotene contents might play a role as it could cause direct photooxidation of chlorophylls and lead to the inhibition of the photosynthetic apparatus. In the meantime, no significant damage was found in leaves of KY131 from June 27 to July 11. In conclusion, the chilling-tolerance mechanism of rice is tightly related to the photosynthetic rate, metabolism of reactive oxygen species, and scavenging system in the vegetative stage., L.-Z. Wang, L.-M. Wang, H.-T. Xiang, Y. Luo, R. Li, Z.-J. Li, C.-Y. Wang, Y. Meng., and Obsahuje bibliografii
Spinach (Spinacia oleracea L. cv. Clermont) leaves grown in open-top chambers and exposed to three different concentrations of ozone were measured for gas exchange, chlorophyll a fluorescence, antioxidant systems, and lipid peroxidation at the end of growing season. High O3 concentration reduced Fv/Fm, indicating that the efficiency in the energy conversion of photosystem 2 (PS2) was altered. The rate of non-cyclic electron transport rate and the capacity to reduce the quinone pool were also affected. The development of non-photochemical quenching was not high enough to decrease the photon excess in the PS2. The limitation of photosynthetic activity was probably correlated with stomata closure and with an increase in intercellular CO2 concentration. Under oxidative stress, superoxide dismutase (SOD) activity was stimulated in parallel with lipid peroxidation. We did not find any differences in the ascorbate (AsA) pool and ascorbate peroxidase (APX) or glutathione reductase (GR) activities between air qualities. Small, but similar responses were observed in spinach leaves exposed to ambient ozone concentration. and A. Calatayud ...[et al.].