Our present work showed that the expression of genes encoding PTOX (terminal oxidase of chlororespiration) and PGR5 (one essential component of cyclic electron transfer) were stimulated by red and blue light, but the stimulation under red light was soon reversed by subsequent far-red light. The expression levels of PTOX and PGR5 under simulated light quality conditions in line with maize-soybean relay strip intercropping (SRI) were obviously lower than those under simulated soybean monocropping (SM), since the lower red:far-red ratio under SRI. Measurements on photosynthetic and chlorophyll fluorescence parameters suggested a decline of assimilatory power supply and a lower nonphotochemical quenching under SRI as compared to SM. In this case, weaker PGR-dependent cyclic electron transfer and chlororespiration under SRI, suggested by lower expression levels of PGR5 and PTOX, could be considered as means of reducing excitation energy dissipation to allocate more power toward CO2 assimilation., X. Sun, X. F. Chen, J. B. Du, W. Y. Yang., and Obsahuje seznam literatury
Expression quantitative trait loci (eQTL) analyses were applied in order to identify genetic factors that are relevant to the expression of a β-isoform Rubisco activase gene in maize, namely ZmRCAβ, in this study. During two years, a maize recombinant inbred line population was measured for ZmRCAβ expression levels at the grain filling stage. Based on a genetic map containing 916 molecular markers, we detected five eQTLs, namely qRCA2.1 on chromosome 2, and qRCA4.1, qRCA4.2, qRCA4.3, and qRCA4.4 on chromosome 4. These eQTLs explained the phenotypic variation ranging from 6.14% to 7.50% with the logarithm of the odd values ranging from 3.11 to 4.96. Based on the position of the eQTLs and ZmRCAβ on the chromosome, qRCA4.2 was inferred as a cis-eQTL and the remaining as a trans-eQTL, suggesting that a combination of both cis- and trans-acting elements might control ZmRCAβ expression. qRCA4.2, qRCA4.3, and qRCA4.4 were repeatedly detected during two years., Q. Sun, Y. Zhang, B. Chen, B. Jia, Z. L. Zhang, M. Cui, X. Kan, H. B. Shi, D. X. Deng, Z. T. Yin., and Obsahuje bibliografii
Extracellular ATP (eATP) has been considered as an important extracellular compound to mediate several physiological processes in plant cells. We investigated the effects of eATP on chlorophyll (Chl) fluorescence characteristics of kidney bean (Phaseolus vulgaris) leaves. Treatment with exogenous ATP at 1 mM showed no significant effect on the maximal photochemical efficiency of PSII. However, the treatment significantly enhanced the values of the PSII operating efficiency (ΦPSII), rate of photosynthetic electron transport through PSII (ETR), and photochemical quenching (qP), while the values of the nonphotochemical quenching (qN) and quantum yield of regulated energy dissipation of PSII (YNPQ) significantly decreased. Our observations indicated that eATP stimulated the PSII photochemistry in kidney bean leaves. Similarly, the treatment with exogenous Ca2+ or H2O2 at 1 mM caused also the significant increase in ΦPSII, qP, and ETR and the significant decrease in qN and YNPQ. LaCl3 (an inhibitor of Ca2+ channels) and dimethylthiourea (a scavenger of H2O2) abolished the effects of exogenous ATP. The results suggest that the role of eATP in enhancing the PSII photochemistry could be related to a Ca2+ or H2O2 signaling pathway., H.-Q. Feng, Q.-S. Jiao, K. Sun, L.-Y. Jia, W.-Y. Tian., and Obsahuje bibliografii
We report here the screening of sixteen cyanobacterial and three green algal strains from Thailand for their potential biohydrogen production. Five filamentous cyanobacterial species, namely Calothrix elenkinii, Fischerella muscicola, Nostoc calcicola, Scytonema bohneri, and Tolypothrix distorta, all possessing nitrogenase activity, showed potentially high biohydrogen production. These five strains showed higher hydrogen production in the absence than in the presence of nitrogen. In particular, F. muscicola had a 17-fold increased hydrogen production under combined nitrogen and sulfur deprived conditions. Among various sugars as a carbon source, glucose at 0.1% (w/v) gave the maximal hydrogen production of 10.9 μmol(H2) mg-1(Chl) h-1 in T. distorta grown in BG11 medium without nitrate. Increasing light intensity up to 250 μmol(photon) m-2 s-1 increased hydrogen production in F. muscicola and T. distorta. Overall results indicate that both F. muscicola and T. distorta have a high potential for hydrogen production amenable for further improvement by using molecular genetics technique., P. Yodsang, W. Raksajit, E.-M. Aro, P. Mäenpää, A. Incharoensakdi., and Obsahuje bibliografické odkazy
New spectral absorption photometry methods are introduced to estimate chlorophyll (Chl) content of corn leaves by smart phones. The first method acquires light passing through a leaf by smartphone camera, compensating for differences in illumination conditions. In order to improve performance of the method, spectral absorption photometry (SAP) with background illumination has been considered as well. Data were acquired by smartphone camera in Iowa State University maize fields. Various indices were extracted and their correlation with Chl content were examined by Minolta SPAD-502. Hue index in SAP reached R2 value of 0.59. However, with light-aided SAP (LASAP), R2 of 0.97 was obtained. Among traits, the vegetation index gave the most accurate indication. We can conclude that the high performance of LASAP method for estimating Chl content, leads to new opportunities offered by smart phones at much lower cost. This is a highly accurate alternative to SPAD meters for estimating Chl content nondestructively., F. Vesali, M. Omid, H. Mobli, A. Kaleita., and Obsahuje seznam literatury
Ferredoxin (Fd) is a small soluble iron-sulfur protein essential in almost all oxygenic photosynthetic organisms. It contains a single [2Fe-2S] cluster coordinated by four cysteine ligands. It accepts electrons from the stromal surface of PSI and facilitates transfer to a myriad of acceptors involved in diverse metabolic processes, including generation of NADPH via Fd-NADP-reductase, cyclic electron transport for ATP synthesis, nitrate reduction, nitrite reductase, sulfite reduction, hydrogenase and other reductive reactions. Fd serves as the central hub for these diverse cellular reactions and is integral to complex cellular metabolic networks. We describe advances on the central role of Fd and its evolutionary role from cyanobacteria to algae/plants. We compare structural diversity of Fd partners to understand this orchestrating role and shed light on how Fd dynamically partitions between competing partner proteins to enable the optimum transfer of PSI-derived electrons to support cell growth and metabolism., J. Mondal, B. D. Bruce., and Obsahuje bibliografické odkazy
We examined the effects of foliar application of various nitrogen (urea) concentrations on gas-exchange and chlorophyll (Chl) fluorescence characteristics in bean plants treated by heat stress (42/30°C, day/night temperatures). Heat stress caused reductions in contents of Chl a, Chl b, and in maximum photochemical efficiency of PSII by 13, 20, and 27%, respectively, regardless of the N treatment. However, N fertilization caused significant increases in these parameters, especially at higher N concentrations. The net photosynthetic rate and stomatal conductance were enhanced by 32, 60, and 69% and by 25, 88, and 100% due to addition of 5, 10, and 15 mM N, respectively. However, gas-exchange parameters were reduced by 24% due to heat stress. N fertilization alleviated adverse effects of heat stress., I. A. Hassan, H. M. Abou Zeid, W. Taia, N. S. Haiba, A. Zahran, R. H. Badr, R. A. El Dakak, E. A. Shalaby., and Obsahuje bibliografii
In this study, we presented the most commonly employed net photosynthetic light-response curves (PN/I curves) fitted by the Solver function of Microsoft Excel. Excel is attractive not only due to its wide availability as a part of the Microsoft Office suite but also due to the increased level of familiarity of undergraduate students with this tool as opposed to other statistical packages. In this study, we explored the use of Excel as a didactic tool which was built upon a previously published paper presenting an Excel Solver tool for calculation of a net photosynthetic/chloroplastic CO2-response curve. Using the Excel spreadsheets accompanying this paper, researchers and students can quickly and easily choose the best fitted PN/I curve, selecting it by the minimal value of the sum of the squares of the errors. We also criticized the misuse of the asymptotic estimate of the maximum gross photosynthetic rate, the light saturation point estimated at a specific percentile of maximum net photosynthetic rate, and the quantum yield at zero photosynthetic photon flux density and we proposed the replacement of these variables by others more directly linked to plant ecophysiology. and F. de A. Lobo ... [et al.].
The kinetics of bacteriochlorophyll fluorescence in intact cells of the purple nonsulfur bacterium Rhodobacter sphaeroides were measured under continuous and pulsed actinic laser diode (808 nm wavelength and maximum 2 W light power) illumination on the micro- and millisecond timescale. The fluorescence induction curve was interpreted in terms of a combination of photochemical and triplet fluorescence quenchers and was demonstrated to be a reflection of redox changes and electron carrier dynamics. By adjustment of the conditions of single and multiple turnovers of the reaction center, we obtained 11 ms-1 and 120 μs-1 for the rate constants of cytochrome c23+ detachment and cyclic electron flow, respectively. The effects of cytochrome c2 deletion and chemical treatments of the bacteria and the advantages of the fluorescence induction study on the operation of the electron transport chain in vivo were discussed., G. Sipka, M. Kis, J. L. Smart, P. Maróti., and Obsahuje bibliografické odkazy
Brassinosteroids (BRs), an important class of plant steroidal hormones, play a significant role in the amelioration of various biotic and abiotic stresses. 24-epibrassinolide (EBR), an active brassinosteroid, was applied exogenously in different concentrations to characterize a role of BRs in tolerance of melon (Cucumis melo L.) to high temperature (HT) stress and to investigate photosynthetic performance of HT-stressed, Honglvzaocui (HT-tolerant) and Baiyuxiang (HTsensitive), melon variety. Under HT, Honglvzaocui showed higher biomass accumulation and a lower index of heat injury compared with the Baiyuxiang. The exogenous application of 1.0 mg L-1 EBR, the most effective concentration, alleviated dramatically the growth suppression caused by HT in both ecotypes. Similarly, EBR pretreatment of HTstressed plants attenuated the decrease in relative chlorophyll content, net photosynthetic rate, stomatal conductance, stomatal limitation, and water-use efficiency (WUE), as well as the maximal quantum yield of PSII photochemistry (Fv/Fm), the efficiency of excitation capture of open PSII center, the effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching coefficient, and the photon activity distribution coefficients of PSI (α). EBR pretreatment further inhibited the increase in intracellular CO2 concentration, leaf transpiration rate, minimal fluorescence of dark-adapted state, nonphotochemical quenching, thermal dissipation, and photon activity distribution coefficients of PSII. Results obtained here demonstrated that EBR could alleviate the detrimental effects of HT on the plant growth by improving photosynthesis in leaves, mainly reflected as up-regulation of photosynthetic pigment contents and photochemical activity associated with PSI. and Y. P. Zhang ... [et al.].