Leaf senescence can be induced by numerous factors. In order to explore the relationship between root respiration and leaf senescence, we utilized different types of phloem girdling to control the root respiration of Alhagi sparsifolia and its physiological response. Our results showed that both girdling and inhibition of root respiration led to a decline of stomatal conductance, photosynthesis, transpiration rate, chlorophyll (Chl) a, Chl b, carotenoid (Car) content, Chl a/b, Chl/Car, water potential, and Chl a fluorescence, as well as to an increase of abscisic acid (ABA), proline, and malondialdehyde content in leaves and to upregulation of senescence-associated gene expression. Our present work implied that both inhibition of root respiration and girdling can induce leaf senescence. In comparison with phloem girdling, the leaf senescence caused by inhibition of root respiration was less significant. The reason for girdling-induced senescence was ABA and carbohydrate accumulation. Senescence induced by inhibition of root respiration occurred due to leaf water stress resulting from inhibition of water absorption., G.-L. Tang, X.-Y. Li, L.-S. Lin, Y. Hu, F.-J. Zeng., and Obsahuje seznam literatury
Environmental stresses, such as cold, heat, salinity, and drought, induce ethylene production and oxidative stress and cause damage in plants. On the other hand, studies have shown that salicylic acid (SA) induced resistance to environmental stresses in plants. In this research, the effects of ethylene on chlorophyll (Chl), carotenoid (Car), anthocyanin, flavonoids, ascorbic acid, dehydroascorbic acid, total ascorbate, lipid peroxidation, and ethylene production in leaves of canola pretreated with SA were studied. The plants were grown in pots until they have four leaves. Leaves were sprayed for two days with three different concentrations of SA (0, 0.5, and 1 mM). The plants were treated for three days with three concentrations of ethylene (0, 50, and 100 ppm). At the end of the ethylene treatments, all examined parameters were measured. The results showed that the ethylene treatments induced lipid peroxidation, while SA mitigated this effect. The ethylene treatment lowered significantly Chl and Car contents and anthocyanin accumulation, but SA alleviated these effects. SA induced an increase in ascorbic acid content in canola plants after the ethylene treatments. Therefore, we concluded that SA played an important role in the alleviation of damages caused by stress conditions. and M. M. Tirani, F. Nasibi, Kh. M. Kalantari.
Elevated atmospheric CO2 concentration [CO2] and the change of water distribution in arid and semiarid areas affect plant physiology and ecosystem processes. The interaction of elevated [CO2] and drought results in the complex response such as changes in the energy flux of photosynthesis. The performance of photosystem (PS) II and the electron transport were evaluated by using OJIP induction curves of chlorophyll a fluorescence and the PN-Ci curves in the two-factor controlled experiment with [CO2] of 380 (AC) or 750 (EC) [μmol mol-1] and water stress by 10% polyethylene glycol 6000. Compared to water-stressed maize (Zea mays L.) under AC, the EC treatment combined with water stress decreased the number of active reaction centers but it increased the antenna size and the energy flux (absorbed photon flux, trapping flux, and electron transport flux) of each reaction center in PSII. Thus, the electron transport rate was enhanced, despite the indistinctively changed quantum yield of the electron transport and energy dissipation. The combination of EC and the water-stress treatment resulted in the robust carboxylation rate without elevating the saturated photosynthetic rate (Pmax). This study demonstrated that maize was capable of transporting more electrons into the carboxylation reaction, but this could not be used to increase Pmax under EC., Y. Z. Zong, W. F. Wang, Q. W. Xue, Z. P. Shangguan., and Obsahuje bibliografii
This study focused on the deleterious effect of anthracene (ANT) and role of a surfactant, Triton (TX-100), in recovery from inhibitory effect of ANT. Fast chlorophyll (Chl) fluorescence measurements were performed in wheat plants. Results revealed that maximum quantum yield of PSII, area over the fluorescence curve, performance index (PI), and reaction centre density was negatively affected by ANT treatment. The effects on PSII quantum efficiency, reaction centre density, absorption, and trapping were partially recovered by TX-100. PSII heterogeneity in terms of PSII antenna heterogeneity, corresponding to PSII α, β, and γ centres, and reducing side, corresponding to QB-reducing and QB-nonreducing centres, were also investigated. The damage caused by ANT to PSII antenna heterogeneity was recovered almost by 100% owing to TX-100., C. Sharma, S. Mathur, R. S. Tomar, A. Jajoo., and Obsahuje bibliografii
Increasing human and industrial activities lead to heavy metal pollution. Heavy metal chromium (Cr) is considered to be a serious environmental contaminant for the biota. Phytotoxic effects of Cr were studied in wheat plants. Growth parameters were largely inhibited as a result of disturbances in the plant cell metabolism in response to Cr toxicity. Chromium toxicity led to decline in a number of active reaction centres of PSII, rate of electron transport, and change in PSII heterogeneity. Chromium did not cause any change in heterogeneity of the reducing side. A significant change in antenna size heterogeneity of PSII occurred in response to Cr toxicity. Chromium seems to have extensive effects on the light harvesting complex of PSII., S. Mathur, H. M. Kalaji, A. Jajoo., and Obsahuje seznam literatury
a1_Photosystem (PS) II particles retaining a high rate of O2 evolution were isolated from the mesophilic filamentous cyanobacterium, Spirulina platensis. To achieve high production of PSII complexes in the cells, irradiance from halogen incandescent lamps was used. Disruption of cells by vibration of glass beads proved to be the most suitable procedure for isolation of thylakoid membranes. The selectivity of detergents for PSII particle preparation rose in the order of Triton X-100 < decyl-β-D-glucopyranoside < dodecyldimethyl-aminooxide < n-heptyl-β-D-thioglucoside < N-dodecyl-N,N-dimethylammonio-3-propane sulphonate < n-octyl-β-thioglycoside < octylglucoside < n-dodecyl-β-D-maltoside. The last four detergents yielded extracts, from which pure PSII particles not contaminated by PSI complexes could be obtained by sucrose-gradient centrifugation (20-45%) at the 43% sucrose level. We assumed both the acceptor and donor sides of the isolated n-dodecyl-β-D-maltoside (DM) particles to be intact due to high oxygen production by DM particles [1,500 meq(e-) mol-1 (Chl) s-1] achieved in the presence of all artificial acceptors tested. The PSII particle fraction from the sucrose gradient was used with immobilized metal (Cu2+) affinity chromatography (IMAC) for the preparation of the PSII core complex. By washing the column with a MES buffer containing MgCl2 and CaCl2, the phycobiliproteins were stripped off. The PSII core complex was eluted in a buffer containing 1% DM, mannitol, MgCl2, NaCl, CaCl2, and ɛ-aminocaproic acid. SDS-PAGE of the core complex provided pure bands of D1 and D2 proteins and PsbO protein from thylakoid membrane, which were used to raise polyclonal antibodies in rabbits. These antibodies recognized D1 and D2 not only as monomers of 31 and 32 kDa proteins, but also as heterodimers of D1, D2 corresponding to the band of 66 kDa on SDS-PAGE. This was in contrast to antibodies of, a2_synthetic determinants, which reacted only with the monomers of D1 and D2 proteins. These negative reactions against heterodimers of D1, D2 supported the hypothesis that dimeric forms of PSII reaction centre proteins have a C-terminal sequence sterically protected against a reaction with specific antibodies., and E. Šetlíková ... [et al.].
A strain of Synechocystis sp. PCC 6803 expressing the yellow fluorescent protein (YFP) fused to the C-terminus of the PsaF subunit of PSI has been constructed and used to isolate native PSI complexes employing the GFP-Trap®, an efficient immunoprecipitation system which recognizes the green fluorescent protein (GFP) and its variants. The protein analysis and spectroscopic characterization of the preparation revealed an isolate of trimeric and monomeric PSI complexes, which showed minimal unspecific contamination as demonstrated by comparison with the wild type control. Interestingly, we detected CP43 subunits of PSII and small amounts of PSII core complexes specifically pulled-down with the YFP-PSI, supporting the association of PSII assembly modules and intermediate assembly complexes with PSI, as observed in our previous studies. The results demonstrate that the GFP-Trap® system represents an excellent tool for studies of PSI biogenesis and interconnection of PSI and PSII assembly processes., A. Strašková, J. Knoppová, J. Komenda., and Obsahuje bibliografické odkazy
Extreme conditions, such as drought, high temperature, and solar irradiance intensity, are major factors limiting growth and productivity of grapevines. In a field experiment, kaolin particle film application on grapevine leaves was examined during two different summer conditions (in 2012 and 2013) with the aim to evaluate benefits of this practice against stressful conditions hindering photochemical processes. We used chlorophyll a fluorescence to investigate attached leaves. Two months after the application, during the hottest midday, the kaolin-treated plants showed by the JIP test significantly higher quantum yield of PSII photochemistry, flux ratios, maximum trapped excitation flux of PSI, absorption flux, electron transport flux, maximum trapped energy flux per cross section, and performance index than plants under control conditions in the warmer year. On the contrary, the treated plants showed a lower initial slope of relative variable fluorescence and a decrease in the absorption and electron transport per cross section. The JIP test showed higher efficiency of PSII in the plants treated with kaolin mainly in 2013 (higher temperature and drought). Our results supported the hypothesis that the accumulation of active PSII reaction centres was associated with decreased susceptibility to photoinhibition in the kaolin-treated plants and with more efficient photochemical quenching. Grapevines in the Douro Region seems to profit from the kaolin application., L.-T. Dinis, H. Ferreira, G. Pinto, S. Bernardo, C. M. Correia, J. Moutinho-Pereira., and Obsahuje seznam literatury