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1762. Photosynthesis in drought-adapted cassava
- Creator:
- Calatayud, P.-A., Llovera, E., Bois, J. F., and Lamaze, T.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll fluorescence, light stress, Manihot exculenta, and young and mature leaves
- Language:
- Multiple languages
- Description:
- After 45 d of limited water supply, cassava (Manihot esculenta Crantz) exhibited pronounced reduction in shoot growth, high leaf fall, and decreased stomatal conductance. However, the water status of the remaining leaves was unaffected. This was combined with an amplified heliotropic response and drooping which minimises radiant energy interception at mid-day, suggesting that leaves are sensitive to high irradiance (I). In well-irrigated plants, CO2-saturated oxygen evolution and net photosynthetic rate (PN) in air were markedly higher (5-fold) in young (expanding) leaves than in mature leaves. Water limitation did not strongly modify CO2-saturated oxygen evolution but it altered PN in air for both types of leaves, although differently. The mature leaves of drought-adapted plants displayed residual rate of P N and deteriorated photosystem 2 (PS2) photochemistry estimated from chlorophyll (Chl) a fluorescence measurements. In young leaves at moderate I, PN was depressed by only 66 % in stressed plants. Moreover, the photochemical quenching of Chl a fluorescence and the quantum efficiency of PS2 photochemistry in young leaves were comparable in both control and stressed plants. In contrast at high I, PN was almost null and marked decreases in the two fluorescence parameters were apparent. Hence the strong heliotropic response and drooping displayed by young leaves under water limitation is an important strategy for avoiding inactivation of PN by high I and therefore for cassava tolerance to drought. and P.-A. Calatayud ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1763. Photosynthesis in leaves of Nicotiana tabacum L. infected with tobacco mosaic virus
- Creator:
- Wilhelmová, N., Procházková, D., Šindelářová, M., and Šindelář, L.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carotenoids, chlorophyll, chlorophyll fluorescence, electron transport, photosynthetic efficiency, photosystem 2, and tobacco
- Language:
- Multiple languages
- Description:
- In tobacco leaves inoculated with tobacco mosaic virus (TMV), changes in chlorophyll (Chl) and carotenoid contents, parameters of slow Chl fluorescence kinetics, i.e. the maximum quantum yield of photosystem (PS2) photochemistry Fv/Fm, the effective quantum yield of photochemical energy conversion in PS2 Φ2, ratio of quantum yields of photochemical and concurrent non-photochemical processes in PS2 Fv/F0, non-photochemical quenching (NPQ), and photochemical activities of isolated chloroplasts from systemically infected tobacco leaves were investigated. We compared two successive stages of infection, the first in the stage of vein clearing at 9th day post inoculation (dpi) and the second at 22nd dpi when two different regions, i.e. light- (LGI) or dark-green (DGI) islands in the infected leaf were apparent and symptoms were fully developed. These two different regions were measured separately. The Chl and carotenoid contents in infected leaves decreased with a progression of infection and were lowest in LGI in the second stage. Also the ratio of Chl a/b declined in similar manner. The maximum quantum yield of PS2 photochemistry Fv/Fm, was decreased in the following order: first stage, DGI, and LGI. The same is true for the ratio Fv/F0. The decrease of Φ2 in infected leaves declined as compared to their controls. On the contrary, NPQ increased in infected leaves, the highest value was found in the first infection stage. Photochemical activities of the whole electron transport chain in isolated chloroplasts dramatically declined with the progression of symptoms, the lowest value was in LGI. Similarly, but to a lesser extent, the activity of PS2 in isolated chloroplasts decreased in infected leaves. Generally, the most marked impairment of the photosynthetic apparatus was manifested in the LGI of infected leaves. and N. Wilhelmová ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1764. Photosynthesis in plants of four tropical species growing under elevated CO2
- Creator:
- Fernández, M. D., Pieters, A., Azkue, M., Rengifo, E., Tezara, W., Woodward, F. I., and Herrera, A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Alternanthera, C3, C3-C4, and CAM plants, Ipomoea, Jatropha, ribulose-1,5-bisphosphate carboxylase/oxygenase, stomatal conductance, and Talinum
- Language:
- Multiple languages
- Description:
- We studied the responses of leaf gas exchange and growth to an increase in atmospheric CO2 concentration in four tropical deciduous species differing in carbon fixation metabolism: Alternanthera crucis, C3-C4; Ipomoea carnea, C3; Jatropha gossypifolia, C3; and Talinum triangulare, inducible-CAM. In the first stage, plants were grown in one open-top chamber at a CO2 concentration of 560±40 μmol mol-1 (EC), one ambient CO2 concentration chamber (AC), and one unenclosed plot (U). In the second stage, plants were grown in five EC chambers (CO2 concentration = 680±30 μmol mol-1), five AC chambers, and five unenclosed plots. During the first weeks under EC in the first stage, plants of all the species had a very marked increase in their maximal net photosynthetic rates (Pmax) of 3.5 times on average; this stimulatory effect was maintained for 11-15 weeks, rates dampening afterward to values still higher than controls for 37 weeks. After a suspension of CO2 enrichment for 6 weeks, an increase in Pmax of EC plants over the controls was found in plants of all the species until week 82 of the experiment. Stomatal conductance (g) showed no response to EC. Carboxylation efficiency decreased in all the species under EC and this was correlated with a decrease in ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) content in all the species except for T. triangulare. During drought Pmax was higher in all species except for 7 triangulare, grown under EC relative to controls. Ecosystem photosynthetic rates at EC were higher than in the controls during the second stage under irrigation as well as after 30 d of drought. and M. D. Fernández ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1765. Photosynthesis in two wheat cultivars differing in salt susceptibility
- Creator:
- El-Shintinawy, F.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- cultivar differences, ethylene, fatty acids, fluorescence emission spectra, polyamines, proline, putrescine, salinity, spermine, and spermidine
- Language:
- Multiple languages
- Description:
- Salinised (150 mM NaCl for 15 d) roots excised from salt sensitive wheat cultivar Giza 163 showed about 15-fold increase in the ratio of Na/K while salt tolerant Sakha 92 exhibited only 7.5-fold increase compared to their control ratios. Root ratio of saturated/unsaturated fatty acids was stimulated twice in the sensitive cultivar versus 1.7-fold increase in the tolerant ones. Salinity enhanced greatly the accumulation of spermine (Spm) and spermidine (Spd) contents associated with a decrease in putrescine (Put) content in both wheat cultivars. Higher ratios of Spm+Spd/Put associated with lower content of proline and low ethylene evolution were detected in shoots and roots of salt tolerant cultivar. Chlorophyll a/b ratio showed an increase from 1.3 in control of both cultivars to 1.6 and 1.4 in stressed Giza 163 and Sakha 92, respectively. A reduced Hill reaction activity (19 %) was observed in stressed chloroplasts isolated from leaves of the tolerant cultivar versus 40 % inhibition in the sensitive ones. Moreover, chloroplasts isolated from stressed leaves of the sensitive cultivar showed about 25 % reduction in fluorescence emission at 685 nm as well as shifts in the peaks in the visible region.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1766. Photosynthesis inhibition during gas exchange oscillations in ABA-treated Helianthus annuus: relative role of stomatal patchiness and leaf carboxylation capacity
- Creator:
- Šantrůček, J., Hronková, M., Květoň, J., and Sage, R. F.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- abscisic acid, CO2 response, cuticular conductance, stomatal conductance, sunflower, and transpiration
- Language:
- Multiple languages
- Description:
- Environmental factors that induce spatial heterogeneity of stomatal conductance, gs, called stomatal patchiness, also reduce the photochemical capacity of CO2 fixation, yet current methods cannot distinguish between the relative effect of stomatal patchiness and biochemical limitations on photosynthetic capacity. We evaluate effects of stomatal patchiness and the biochemical capacity of CO2 fixation on the sensitivity of net photosynthetic rate (PN) to stomatal conductance (gs), θ (θ = δP N/gs). A qualitative model shows that stomatal patchiness increases the sensitivity θ while reduced biochemical capacity of CO2 fixation lowers θ. We used this feature to distinguish between stomatal patchiness and mesophyll impairments in the photochemistry of CO2 fixation. We compared gas exchange of sunflower (Helianthus annuus L.) plants grown in a growth chamber and fed abscisic acid, ABA (10-5 M), for 10 d with control plants (-ABA). PN and gs oscillated more frequently in ABA-treated than in control plants when the leaves were placed into the leaf chamber and exposed to a dry atmosphere. When compared with the initial CO2 response measured at the beginning of the treatment (day zero), both ABA and control leaves showed reduced PN at particular sub-stomatal CO2 concentration (ci) during the oscillations. A lower reduction of P N at particular g s indicated overestimation of ci due to stomatal patchiness and/or omitted cuticular conductance, gc. The initial period of damp oscillation was characterised by inhibition of chloroplast processes while stomatal patchiness prevailed at the steady state of gas exchange. The sensitivity θ remained at the original pre-treatment values at high gs in both ABA and control plants. At low gs, θ decreased in ABA-treated plants indicating an ABA-induced impairment of chloroplast processes. In control plants, gc neglected in the calculation of gs was the likely reason for apparent depression of photosynthesis at low gs. and J. Šantrůček ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1767. Photosynthesis of a temperate fallow C3 herbaceous ecosystem: measurements and model simulations at the leaf and canopy levels
- Creator:
- Gouasmi, M., Mordelet, P., Demarez, V., Gastellu-Etchegorry, J.-P., Le Dantec, V., Dedieu, G., Menaut, J.-C., Calvet, J.-C., and Lamaze, T.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- photosynthesis
- Language:
- Multiple languages
- Description:
- The objectives of the study were to characterize photosynthesis of temperate fallow C3 herbaceous species and examine the performance of a simple photosynthesis model (based on the Farquhar's equations) to simulate carbon fluxes at the leaf and canopy levels. The maximum rate of carboxylation at 25°C (V m0) was estimated for sunlit leaves using in situ gas exchange data under saturating irradiance. Throughout the seasons, leaf measurements indicate that values of V m0 were similar for the four major species of the fallow. The rate declined from March (100 µmol m-2 s-1) to July (50 µmol m-2 s-1) and remained almost constant until November. The maximum quantum yield estimated for Potentilla reptans L. (dominant species) was 0.082 mol(CO2) mol-1(photon absorbed), similar to values already published for C3 species. Leaf area index (LAI) increased from winter (less than 0.2 m2 m-2) to spring (up to 4 m2 m-2). Rates of canopy photosynthesis (measured with a canopy chamber) strongly depended on LAI and temperature, in addition to irradiance. They reached a maximum of 25 µmol m-2 s-1 and were intermediate between those published for C4 grassland or cultivated species, and on woody species. At leaf level, simulations gave realistic predictions. At canopy level, the model had the ability to reproduce the effects of environmental and seasonal conditions. However, simulations underestimated the photosynthetic activity of the fallow canopy. and M. Gouasmi ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1768. Photosynthesis of a yellow-green mutant line in maize
- Creator:
- Zhong, X. M., Sun, S. F., Li, F. H., Wang, J., and Shi, Z. S.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, gene mutation, photochemical reaction, potential productivity, 2, and 581
- Language:
- Multiple languages
- Description:
- This study compared the relationship between chlorophyll (Chl) content, gas exchange, Chl fluorescence characteristics, and leaf color, using paired near-isogenic lines (NILs) of a medium-green leaf inbred line SN12 and a yellow-green leaf mutant SN62 to explore the photosynthesis of the yellow-green mutant. The SN62 was found in a female parent, Xianyu 335, which grew normally, although there were small yellow spots on the leaves at the seedling stage and yellow-green leaves appeared from the seedling to the maturation stage. The results indicated that Chl a (b), quantum efficiency of PSII, and maximal quantum yield of PSII photochemistry of SN62 were significantly lower than those of SN12, but there were almost no differences in the net photosynthetic rate (P N). There was no significant correlation between Chl a (b) and P N of inbred lines with different leaf colors. In the reproductive stage, photochemical quenching, effective quantum yield of PSII photochemistry, and the electron transport rate of SN62 increased obviously, and all parameter values exceeded the values of SN12. It explained that increasing the openness of the PSII reaction center was able to compensate for the lower Chl content, which was beneficial for harvesting more light energy for photochemical reactions. It also ensured that P N was not reduced., X. M. Zhong, S. F. Sun, F. H. Li, J. Wang, Z. S. Shi., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1769. Photosynthesis of cockspur [Echinochloa crus-galli (L.) Beauv.] at sites of naturally elevated CO2 concentration
- Creator:
- Vodnik, D., Pfanz, H., Maček, I., Kastelec, D., Lojen, S., and Batič, F.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carbon dioxide springs, chlorophyll, CO2 compensation concentration, intercellular CO2 concentration, net photosynthetic rate, plant height, stomatal conductance, and δ13C
- Language:
- Multiple languages
- Description:
- High abundance of cockspur (Echinochloa crus-galli) at the geothermal carbon dioxide spring area in Stavešinci indicates that this species is able to grow under widely varying CO2 concentrations. Living cockspur plants can even be found very close to gas-releasing vents where growth is significantly reduced. Plant height correlated well with CO2 exposure. The δ13C value of the CO2 spring air was -3.9 ‰ and δ13C values of high-, medium-, and low-CO2 plants were -10.14, -10.44, and -11.95 ‰, respectively. Stomatal response directly followed the prevailing CO2 concentrations, with the highest reduction of stomatal conductance in high CO2 concentration grown plants. Analysis of the curves relating net photosynthetic rate to intercellular CO2 concentration (PN-Ci curves) revealed higher CO2 compensation concentration in plants growing at higher CO2 concentration. This indicates adjustment of respiration and photosynthetic carbon assimilation according to the prevailing CO2 concentrations during germination and growth. There was no difference in other photosynthetic parameters measured. and D. Vodnik ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1770. Photosynthesis of Hedera canariensis var. azorica variegated leaves as affected by ozone
- Creator:
- Soldatini, G. F., Nali, C., Guidi, L., and Lorenzini, G.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll, fluorescence, ivy, net photosynthetic rate, stomatal conductance, and transpiration
- Language:
- Multiple languages
- Description:
- A differential response to long-term ozone exposures (50 and 100 mm3 m-3) was observed in the green and white areas of variegated leaves of Hedera canariensis var. azorica L. In green tissue the photosynthetic activity was depressed via a stomatal mechanism, and in white regions no effect was observed. Chlorophyll fluorescence parameters remained unchanged in green portions, whereas in the white ones Fm and Fv/Fm significantly diminished following ozone fumigation. and G. F. Soldatini ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public