Ginkgo biloba L. is a large tree native in China with evolutionary affinities to the conifers and cycads. However unlike conifers, the gymnosperm G. biloba is not able to synthesize chlorophyll (Chl) in the dark, in spite of the presence of genes encoding subunits of light-independent protochlorophyllide oxidoreductase (DPOR) in the plastid genome. The principal aims of the present study were to investigate the presence of DPOR protein subunits (ChlL, ChlN, ChlB) as well as the key regulatory step in Chl formation: aminolevulinic acid (ALA) synthesis and abundance of the key regulatory enzyme in its synthesis: glutamyl-tRNA reductase (GluTR). In addition, functional stage of photosynthetic apparatus and assembly of pigment-protein complexes were investigated. Dark-grown, illuminated and circadian-grown G. biloba seedlings were used in our experiments. Our results clearly showed that no protein subunits of DPOR were detected irrespective of light conditions, what is consistent with the absence of Chl and Chl-binding proteins (D1, LHCI, LHCIIb) in the dark. This correlates with low ALA-synthesizing capacity and low amount of GluTR. The concentration of protochlorophyllide (Pchlide) in the dark is low and non-photoactive form (Pchlide633) was predominant. Plastids were developed as typical etioplasts with prollamelar body and few prothylakoid membranes. Continual illumination (24 h) only slightly stimulated ALA and Chl synthesis, although Pchlide content was reduced. Prollamelar bodies disappeared, but no grana were formed, what was consistent with the absence of D1, LHCI, LHCIIb proteins. Lightinduced development of photosynthetic apparatus is extremely slow, as indicated by Chl fluorescence and gas exchange measurements. Even after 72 h of continuous illumination, the values of maximum (Fv/Fm) and effective quantum yield (ΦPSII) and rate of net photosynthesis (PN) did not reach the values comparable with circadian-grown plants. and A. Pavlovič ... [et al.].
We tested whether cheap and quick chlorophyll (Chl) fluorescence can be used in ecophysiological field studies as proxies for
gas-exchange measurements. We measured net photosynthetic rate at saturating irradiance and ambient atmospheric CO2 concentrations (PNsat), maximum carboxylation rate (Vcmax), maximum quantum yield of PSII (Fv/Fm), the performance index (PIabs), leaf nitrogen (Narea), and carbon isotope discrimination (Δ13C) within four herbaceous species along two elevational gradients. We analysed the relationship between Chl fluorescence and gas-exchange parameters and their link to indirect assessment of plant performance via ecophysiological traits. Fv/Fm showed no relationship to PNsat and only weak relationships to Vcmax. PIabs was positively related to PNsat and Vcmax. PIabs, PNsat, and Vcmax were positively associated with Narea and negatively to Δ13C, whereas Fv/Fm showed no relationship to Narea and a positive to Δ13C. Thus, PIabs might be suitable to characterize the photosynthetic activity when aiming on large numbers of samples., S. F. Bucher, M. Bernhardt-Römermann, C. Römermann., and Obsahuje bibliografii
Changes in chloroplastidic pigments, gas exchange and carbohydrate concentrations were assessed during the rapid initial expansion of C. guianensis leaflet. Leaves at metaphyll stage were tagged and assessments were carried out 14, 17, 20, 23, 27, and 31 days later. Pigments synthesis, distribution and accumulation were uniform among leaflet sections (basal, median and apical). Chlorophyll (Chl) a, Chl b, Chl (a+b), and total carotenoids (Car) concentrations were significantly increased after 27 days from metaphyll, and the most expressive increases were parallel to lower specific leaflet area. Chl a/b was lower on day 14 and it was increased on subsequent days. Negative net photosynthesis rate (PN), and the lowest stomatal conductance (gs) and transpiration (E) were registered on day 14, following significant increases on subsequent days. The Chl (a+b) and Chl a effects on PN were more expressive until day 20. Intercellular to ambient CO2 concentration ratio (Ci/Ca) was higher on day 14 and lower on subsequent days, and no stomatal limitation to CO2 influx inside leaflets was observed. Leaflet temperature was almost constant (ca. 35°C) during leaflet development. Sucrose and starch concentrations were increased in parallel to increases in PN. Altogether, these results highlight the main physiological changes during C. guianensis leaflet expansion and they should be considered in future experiments focusing on factors affecting PN in this species. and F. K. C. Moraes ... [et al.].
Fifty-d-old poplar (Populus deltoides L.) plants were irrigated with 50-200 mM NaCl. 100 and 200 mM NaCl significantly reduced net photosynthetic rate, chlorophyll and carotenoid contents, leaf area, dry matter accumulation, and harvest index (HI) in all tested poplar clones (Bahar, S7C15, and WSL22). Clone S7C15 was more tolerant to salinity than the other clones. and M. Singh, M. Jain, R. C. Pant.
The combined effects of UV-B irradiation and foliar treatment with selenium on two buckwheat species, common (Fagopyrum esculentum Moench) and tartary [Fagopyrum tataricum (L.) Gaertn.] buckwheat, that underwent different intensity of breeding, were examined. Plants grown outdoors under three levels of UV-B radiation were studied for 9 weeks, from sowing to ripening. At week 7 they were sprayed with solution containing 1 g(Se) m-3 that presumably mitigates UV-B stress. Morphological, physiological, and biochemical parameters of the plants were monitored. Elevated UV-B radiation, corresponding to a 17 % reduction of the ozone layer, induced synthesis of UV absorbing compounds. In both buckwheat species it also caused a reduction in amounts of chlorophyll a during the time of intensive growth, an effect, which was increased in tartary buckwheat in the presence of selenium. The respiratory potential, measured as terminal electron transport system activity, was lower in plants subjected to enhanced UV-B radiation during the time of intensive growth. The effective quantum yield of photosystem 2 was also reduced due to UV-B radiation in both buckwheat species and was mitigated by the addition of Se. Se treatment also mitigated the stunting effect of UV-B radiation and the lowering of biomass in common buckwheat. and B. Breznik ... [et al.].
The relationships between drought response and anatomical/physiological properties were assessed in two poplar clones belonging to the Aigeros section: Populusxeuramericana clone Dorskamp (drought-tolerant) and clone Luisa Avanzo (drought-sensitive). Cuttings of both clones were exposed for 12 h to 0 mM (control). 50 mM (osmotic potential -0.112 MPa), and 150 mM (-0.336 MPa) mannitol. In control, Dorskamp had smaller stomata than Luisa Avanzo, one or two layers of palisade cells, a spongy mesophyll, and high concentrations of antioxidative compounds (ascorbate, glutathione). After exposure to 50 or 150 mM mannitol, both clones closed their stomata: leaf conductance and opening of stomata decreased. When exposed to 50 mM mannitol, net photosynthetic rate (PN) and chlorophyll (Chl) and total solute contents remained stable; ribulose-1,5-bisphosphate carboxylase/-oxygenase activity, Chl synthesis and turn-over, ascorbate peroxidase and glutathione reductase activities were less affected in Dorskamp than in Luisa Avanzo. Following an exposure to 150 mM mannitol, Dorskamp exhibited higher PN and higher contents of antioxidants (ascorbate, glutathione) and antioxidative enzymes (ascorbate peroxidase, glutathione reductase) than Luisa Avanzo. Hence the drought-tolerant poplar was able to better avoid and tolerate osmotic stress. and M. Courtois, E. Boudouresque, G. Guerrier.
The present piece of work highlights the comparative effects of two active forms of brassinosteroids (BRs), 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL), on growth parameters, carbonic anhydrase activity and photosynthetic parameters in Lycopersicon esculentum (cv. K-21) sampled at 45 (24 h after spray) and 60 days after sowing, under natural conditions. Out of the two active forms of BR, EBL proved better than HBL in improving the above parameters, when applied as foliar spray. Of the three concentrations (10-6 M, 10-8 M or 10-10 M) of HBL and EBL, 10-8M proved best in both cases. and S. Hayat ... [et al.].
A field study was conducted with the aim to elucidate photosynthetic responses of five emmer hulled wheat (Triticum turgidum ssp. dicoccum) accessions to 30 (N-limited) and 100 kg(N) ha-1
(N-sufficient) conditions at control and drought stress (irrigation after 30-40% and 60-70% depletion of available soil water, respectively). Chlorophyll (Chl) a and Chl b concentrations of the emmer wheats remained unchanged but net photosynthetic rate and dry mass increased and decreased, respectively, when received a sufficient amount of N. Smaller drought-induced decreases in Chl concentration, membrane stability index, and dry mass were concomitant to a greater decrease in intercellular CO2 concentration of emmer compared to the durum (Triticum turgidum) and bread wheats (Triticum aestivum). The lack of negative effect of insufficient N on Chl concentration and dry mass of emmer wheat suggests that this type of wheat possesses an obvious potential for organic farming., M. Vaghar, P. Ehsanzadeh., and Obsahuje bibliografii
The seedlings of wheat were treated by salt-stress (SS, molar ratio of NaCl: Na2SO4 = 1:1) and alkali-stress (AS, molar ratio of NaHCO3: Na2CO3 = 1:1). Relative growth rate (RGR), leaf area, and water content decreased with increasing salinity, and the extents of the reduction under AS were greater than those under SS. The contents of photosynthetic pigments did not decrease under SS, but increased at low salinity. On the contrary, the contents of photosynthetic pigments decreased sharply under AS with increasing salinity. Under SS, the changes of net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were similar and all varied in a single-peak curve with increasing salinity, and they were lower than those of control only at salinity over 150 mM. Under AS, PN, gs, and E decreased sharply with rising salinity. The decrease of gs might cause the obvious decreases of E and intercellular CO2 concentration, and the increase of water use efficiency under both stresses. The Na+ content and Na+/K+ ratio in shoot increased and the K+ content in shoot decreased under both stresses, and the changing extents under AS were greater than those under SS. Thus SS and AS are two distinctive stresses with different characters; the destructive effects of AS on the growth and photosynthesis of wheat are more severe than those under SS. High pH is the key feature of the AS that is different from SS. The buffer capacity is essentially the measure of high pH action on plant. The deposition of mineral elements and the intracellular unbalance of Na+ and K+ caused by the high pH at AS might be the reason of the decrease of PN and gs and of the destruction of photosynthetic pigments. and C. W. Yang ... [et al.].
Photosynthetic characteristics of two hybrid rice combinations, Peiai 64S/E32 and Shanyou 63, were compared at the panicle differentiation stage. As compared with Shanyou 63, the new combination Peiai 64S/E32 showed a significantly higher net photosynthetic rate (PN), apparent quantum yield of carbon assimilation (Φc), carboxylation efficiency (CE), and photorespiratory rate (RP) as well as leaf chlorophyll content, but a significantly lower dark respiration rate (RD) and compensation irradiance (Ic). It also showed a slightly higher photochemical efficiency (Fv/Fm and ΔF/Fm') of photosystem 2, a lower non-photochemical quenching (qN), and a similar CO2 compensation concentration (Γ) as compared to Shanyou 63. and Hua Jiang ... [et al.].