a1_Two full-length cDNAs (SGrca1 and SGrca2) encoding ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase (RCA) were cloned from a heterophyllous aquatic plant, Sagittaria graminea, using Rapid-Amplification of cDNA Ends (RACE). SGrca1 contains a 1,320 bp open reading frame encoding a protein of 440 amino acids, and SGrca2 is exactly identical to SGrca1 except for 330 bp missing in the middle of SGrca1. Sequence analysis of cDNA and genomic DNA indicated both two cDNAs were generated from a common gene via alternative splicing. The deduced amino acid sequence encoded by SGrca1 showed 75-82% identity with other RCAs from higher plants and showed high homology in three highly conserved motifs associated with ATP-binding sites. RT-PCR analysis suggested both SGrca1 and SGrca2 were expressed in green tissues. During a 14 h light/10 h dark photoperiod, both aerial and submerged leaves exhibited the similar expression pattern of SGrca1 and SGrca2 with SGrca1 as the dominant form, but the accumulation of both SGrca1 and SGrca2 mRNA was significantly inhibited in the submerged leaves., a2_Western blot analysis showed that both SGrca1 and SGrca2 had their translation products, the 43 kDa form and the 31 kDa form expressing in leaves. Interestingly, the aerial leaves expressed higher amount of the 43 kDa form compared with the 31 kDa form, while it was reversed in the submerged leaves. The results demonstrated that both environments regulated the RCA gene expression at both transcriptional and posttranscriptional level. In addition, co-immunoprecipitation assay revealed that the isolated Rubisco-RCA complex contained both the 43 and 31 kDa forms, and the proportion of the 31 kDa form was obviously enhanced in the submerged leaves. The results indicated that both the 43 kDa and 31 kDa forms were involved in Rubisco and RCA interaction and the increased incorporation of the 31 kDa form was associated with submerged photosynthetic environment., D. Wang, S. Z. Xie, J. Yang, Q. F. Wang., and Obsahuje bibliografii
The chlorophyll a/b-binding protein (CAB) serves in both photosystems (PS), I and II, as a coordinator of antenna pigments in the light-harvesting complex (LHC). The CABs constitute abundant and important proteins in the thylakoid membrane of higher plants. In our study, five CAB genes, which contained full-length cDNA sequences from the 4-year-old ginseng leaves (Panax ginseng Meyer), were isolated and named PgCAB. Phylogenetic comparison of the members of the subfamily between ginseng and higher plants, including Arabidopsis, revealed that the putative functions of these ginseng CAB proteins were clustered into the different family of Arabidopsis CABs; two PgCABs in LHCII family and three PgCABs in LHCI family. The expression analysis of PgCABs consistently showed dark-dependent inhibition in leaves. Expression analysis during abiotic stress identified that PgCAB genes responded to heavy metal, salinity, chilling, and UV stresses differently, suggesting their specific function during photosynthesis. This is the first comprehensive study of the CAB gene family in P. ginseng., J. Silva, Y. J. Kim, J. Sukweenadhi, S. Rahimi, W. S. Kwon, D. C. Yang., and Seznam literatury
The chlorophyll (Chl) fluorescence imaging technique was applied to cashew seedlings inoculated with the fungus Lasiodiplodia theobromae to assess any disturbances in the photosynthetic apparatus of the plants before the onset of visual symptoms.
Two-month-old cashew plants were inoculated with mycelium of L. theobromae isolate Lt19 or Lt32. Dark-adapted and light-acclimated whole plants or previously labelled, single, mature leaf from each plant were evaluated weekly for Chl fluorescence parameters. From 21 to 28 days, inoculation with both isolates resulted in the significantly lower maximal photochemical quantum yield of PSII (Fv/Fm) than those for control samples, decreasing from values of 0.78 to 0.62. In contrast, the time response of the measured fluorescence transient curve from dark-acclimated plants increased in both whole plants and single mature leaves in inoculated plants compared with controls. The Fv/Fm images clearly exhibited photosynthetic perturbations 14 days after inoculation before any visual symptoms appeared. Additionally, decays in the effective quantum yield of PSII photochemistry and photochemical quenching coefficient were also observed over time. However, nonphotochemical quenching increased during the evaluation period. We conclude that Fv/Fm images are the effective way of detecting early metabolic perturbations in the photosynthetic apparatus of cashew seedlings caused by gummosis in both whole plants and single leaves and could be potentially employed in larger-scale screening systems., C. R. Muniz, F. C. O. Freire, F. M. P. Viana, J. E. Cardoso, C. A. F. Sousa, M. I. F. Guedes, R. van der Schoor, H. Jalink., and Obsahuje bibliografii
Non-destructive and rapid method for assessment of leaf photosynthetic characteristics is needed to support photosynthesis modelling and growth monitoring in crop plants. We determined the quantitative relationships between leaf photosynthetic characteristics and canopy spectral reflectance under different water supply and nitrogen application rates. The responses of reflectance at red radiation (wavelength 680 nm) to different water contents and nitrogen rates were parallel to those of leaf net photosynthetic rate (PN). The relationships of reflectance at 680 nm and ratio index of R(810,680) (near infrared/red, NIR/R) to PN of different leaf positions and leaf layers in rice indicated that the top two full leaves were the best leaf positions for quantitative monitoring of leaf PN with remote sensing technique, and the ratio index R(810,680) was the best ratio index for evaluating leaf photosynthetic characteristics in rice. Testing of the models with independent data sets indicated that R(810,680) could well estimate PN of top two leaves and canopy leaf photosynthetic potential in rice, with the root mean square error of 0.25, 0.16, and 4.38, respectively. Hence R(810,680) can be used to monitor leaf photosynthetic characteristics at different growth stages of rice under diverse growing conditions. and Y. Tian, Y. Zhu, W. Cao.
We investigated the effect of moderate Cu2+ and Cd2+ stress by applying chlorophyll (Chl) fluorescence and P700 absorbance measurements to monitor the photosynthetic electron transport activity of 3-week-old Pisum sativum L. cv. Petit Provençal plants grown in a modified Hoagland solution containing 50 μM CuSO4 or 5 μM CdCl2. Both heavy metals caused a slight inhibition in PSII photochemistry as indicated by the decrease in the effective quantum efficiency of PSII (ΦPSII), the maximum electron transport capacity (ETRmax), and the maximum quantum yield for electron transport (α). PSI photochemistry was also affected by these heavy metals. Cu2+ and Cd2+ decreased the quantum efficiency of PSI (ΦPSI) as well as the number of electrons in the intersystem chain, and the Cu2+ treatment significantly reduced the number of electrons from stromal donors available for PSI. These results indicate that PSII and PSI photochemistry of pea plants are both sensitive to moderate Cu2+ and Cd2+ stress, which in turn is easily detected and monitored by Chl fluorescence and P700 absorbance measurements. Therefore, monitoring the photochemistry of pea plants with these noninvasive, yet sensitive techniques offers a promising strategy to study heavy metal toxicity in the environment., B. Wodala ... [et al.]., and Obsahuje bibliografii
Monolayer films of phycobilisome-thylakoid membrane complexes isolated from Spirulina platensis were prepared at air/aqueous solution interface by using the Langmuir-Blodgett technique. The film preparation was optimized with 0.5 M phosphate buffer (pH 7.0) as sub-phase at 20 °C. The monolayer was transferred into grids and into mica surface for observing the surface image of the complexes by transmission electron microscopy and atomic force microscope, respectively. The shape of complexes was disk-like with the diameter of about 50 nm and the thickness of about 35 nm. The absorption and fluorescence spectra of the complexes in the monolayer were consistent with those in buffer solution, which suggests that the complexes in the monolayer preserve the basic functional groups of photosynthetic apparatus and can be used as a model to investigate the structural connection and functional association of the light-harvesting antenna with the reaction centres. and D.-H. Li ... [et al.].
Morpho-anatomical leaf traits and photosynthetic activity of two alpine herbs, Podophyllum hexandrum (shade-tolerant) and Rheum emodi (light-requiring), were studied under field (PAR>2 000 µmol m-2 s-1) and greenhouse (PAR 500 µmol m-2 s-1) conditions. Mesophyll thickness, surface area of mesophyll cells facing intercellular spaces (Smes), surface area of chloroplasts facing intercellular spaces (Sc), intercellular spaces of mesophyll cells (porosity), photon-saturated rate of photosynthesis per unit leaf area (PNmax), and ribulose-1,5-bisphosphate carboxylase/oxygenase activity decreased in the greenhouse with respect to the field and the decreases were significantly higher in R. emodi than in P. hexandrum. P. hexandrum had lower intercellular CO2 concentration than R. emodi under both irradiances. The differences in acclimation of the two alpine herbs to low irradiance were due to their highly unlikely changes in leaf morphology, anatomy, and PNmax which indicated that the difference in radiant energy requirement related to leaf acclimation had greater impact under low than high irradiance. and S. Pandey, N. Kumar, R. Kushwaha.
Morpho-physiological and biochemical analyses were carried out in eight diverse indigenous muskmelon (Cucumis melo L.) genotypes exposed to different degrees of water deficit (WD). The ability of genotypes MM-7, and especially MM-6, to counteract better the negative effect of WD was associated with maintaining higher relative water content (RWC), photosynthetic rate, efficiency of PSII, and photosynthetic pigments compare to other genotypes. Furthermore, MM-6 showed a better ability to maintain cellular homeostasis than the others. It was indicated by a stimulated antioxidative defense system, i.e., higher activities of antioxidant enzymes, accumulation of nonenzymatic antioxidants together with lower concentration of reactive oxygen species and malondialdehyde. However, the genotypes MM-2 and MM-5 suffered greatly due to WD and showed reduced RWC, photosynthetic rates, pigment content, and exhibited higher oxidative stress observed as lower antioxidant enzyme activities., W. A. Ansari, N. Atri, B. Singh, P. Kumar, S. Pandey., and Obsahuje bibliografii
a1_The recomposition of deforested environments demands the acclimation of seedlings in nurseries. This process induces changes in physiological, anatomical, and morphological traits of plants, favouring their establishment after transplantation to the field. The present study aimed to verify the influence of full-sun acclimation on seedling hardiness. For the purpose, leaf gas-exchange, plant anatomical and morphological parameters of three tree species [Ceiba speciosa (A. St.-Hil.) Ravenna (Malvaceae), Croton floribundus Spreng. (Euphorbiaceae), and Cecropia pachystachya Trecul (Urticaceae)], which are used for reforestation in the Brazilian Atlantic biome, were evaluated. Seedlings were grown under 40% of total PPFD (shaded control) and under full sun (acclimated) for 168 days. The acclimation process induced a higher leaf production rate in C. speciosa and C. floribundus, whereas C. pachystachya seedlings replaced their leaves quickly, irrespective of the light conditions. The newly developed leaves of all three species presented a lower area and thicker palisade parenchyma, resulting in a reduced specific leaf area. The seedlings of C. speciosa and C. pachystachya showed increases in light-saturated net photosynthesis and transpiration rates, whereas water-use efficiency generally remained unchanged in all three species. The full-sun acclimated seedlings of C. pachystachya showed a reduced relative growth rate, lower height/stem diameter (H/D) and shoot to root dry mass ratios, characteristics that may result in greater physical resistance and ability for water and nutrient uptake to support the higher transpiratory demand under full sun. The reduction of the H/D ratio also occurred in the acclimated seedlings of C. speciosa., a2_The seedlings of C. floribundus showed few changes during acclimation, but they did not seem to be affected by excessive light. In spite of the observed differences among the three species, all of them developed hardiness characteristics, mainly related to leaf anatomy, which should favour their establishment after transplantation to the field., A. K. Calzavara, E. Bianchini, T. Mazzanatti, H. C. Oliveira,
R. Stolf-Moreira, J. A. Pimenta., and Obsahuje seznam literatury