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2292. Shade effect alters leaf pigments and photosynthetic responses in Norway spruce (Picea abies L.) grown under field conditions

Creator:
Bertamini, M., Muthuchelian, K., and Nedunchezhian, N.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence, diphenyl carbazide, donor side, electron transport, NH2OH, photosystems 1 and 2, polypeptides, and ribulose-1,5-bisphosphate carboxylase
Language:
Multiple languages
Description:
The contents of chlorophyll (Chl) and carotenoids (Car) per fresh mass were lower in shade needles than in sun needles. Ribulose-1,5-bisphosphate carboxylase (RuBPC) activity and contents of soluble proteins were also significantly lower in shade needles. In isolated thylakoids, a marked lower rate of whole chain and photosystem (PS) 2 activities were observed in shade needles. Smaller lower rate of PS1 activity was also observed in shade needles. The artificial exogenous electron donors, diphenyl carbazide (DPC) and NH2OH, significantly restored the loss of PS2 activity in shade needles. Similar results were obtained when Fv/Fm was evaluated by Chl fluorescence measurements. The marked lower rate of PS2 activity in shade needles was due to the lower contents of 47, 33, 28-25, 23, and 17 kDa polypeptides. This conclusion was confirmed by immunological studies showing that the content of the 33 kDa protein of the watersplitting complex was diminished significantly in shade needles. and M. Bertamini, K. Muthuchelian, N. Nedunchezhian.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2293. Shade mitigates photoinhibition and enhances water use efficiency in kiwifruit under drought

Creator:
Montanaro, G., Dichio, B., and Xiloyannis, C.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
carbon gain, excessive radiation, photosynthesis, semi-arid condition, shade, stomatal limitation, and water use efficiency
Language:
Multiple languages
Description:
We tested the hypotheses that a reduction of incident light of 50 % over sun-acclimated leaves of water stressed kiwifruit (Actinidia deliciosa var. deliciosa) would (1) reduce stomatal limitations to carbon supply and (2) mitigate the inactivation of the primary photochemistry associated with photosystem (PS) II, thereby this increases carbon gain and water-use efficiency (WUE). Groups of field-grown vines were either shaded or left naturally exposed and subjected to progressive water stress in order to study moderately and severely droughted vines, while other groups were well irrigated. Daily variations in leaf gas exchange and midday chlorophyll (Chl) a fluorescence were determined once plants had -0.6 MPa (moderate stress) and -1.0 MPa pre-down leaf water potential (severe stress). Variations in Chl pigment content and specific leaf area (SLA) are also discussed. Results reveal that 50 % shade application maintained efficiency of PSII close to 0.8 even under severe drought so that to prevent its large decline (0.65) recorded in sunlit leaves. Under moderate stress level stomata behaviour dominated upon metabolic impairments of PSII. Reduction of irradiance increased WUE (15-20 %) in droughted vines, representing a valuable intervention to save photosynthetic apparatus and improve WUE in vines experiencing typical Mediterranean summer stresses. and G. Montanaro, B. Dichio, C. Xiloyannis.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2295. Short- versus long-term effects of elevated CO2 on night-time respiration of needles of Scots pine (Pinus sylvestris L.)

Creator:
Jach, M. E. and Ceulemans, R.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
carbon, C/N, direct and indirect effects, nitrogen, soluble sugars, starch, and specific leaf area
Language:
Multiple languages
Description:
Dark respiration rate in the night (R D) was measured in five-year-old Scots pine (Pinus sylvestris L.) trees grown for two years under ambient (AC) and elevated (AC + 400 µmol mol-1 = EC) CO2 concentrations in open top chambers. Two needle age classes (i.e., current-year and one-year-old) were measured at AC and EC in both AC- and EC-grown pines. Additionally different chemical characteristics were determined on the needles, such as nitrogen (N), carbon (C), starch, and soluble sugar concentrations as well as specific leaf area. The direct, short-term and indirect, long-term effects of EC on R D for the two needle age classes were examined. R D was expressed on a per needle area, needle mass, N, C, and C/N bases. Direct effects were only pronounced in the AC treatment where inhibition of R D was found at EC in both current- and one-year-old needles. Indirect effects were only significant in one-year-old needles where a decrease was found in the EC grown trees as compared with AC ones when R D was expressed per unit needle mass, C, or C/N. R D per unit needle area and needle N were not sensitive to long-term EC, in any needle age class. Long-term EC treatment also influenced the response of the two needle age classes. One-year-old needles from the EC treatment had significantly lower R D than current-year needles, but no such response was observed in the AC treatment. Our experiment re-emphasised the importance of expressing R D on different bases for a correct interpretation of the responses to EC. Moreover, we showed that different needle age classes can respond differently to a CO2 enrichment. and M. E. Jach, R. Ceulemans.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2296. Short-term chromium(VI) stress induces different photosynthetic responses in two duckweed species, Lemna gibba L. and Lemna minor L.

Creator:
Oláh, V., Lakatos, G., Bertók, C., Kanalas, P., Szöllösi, E., Kis, J., and Mészáros, I.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
botanika, botany, chlorophyll fluorescence, Cr(VI), duckweed, electron transport rate, Lemna gibba, Lemna minor, nonphotochemical quenching, and rapid light curves
Language:
Multiple languages
Description:
Physiological responses of two duckweed species, Lemna gibba and Lemna minor, to hexavalent chromium [Cr(VI)] were studied in axenic cultures using short-term (48 h) treatments by K2Cr2O7 (0-200 μM). Chlorophyll (Chl) fluorescence parameters and photosynthetic pigment composition of plants were screened to determine the effects of Cr(VI) exposures. The two duckweed species exhibited different sensitivity in the applied Cr(VI) concentration range. Chl fluorescence parameters of dark-adapted and light-adapted plants and electron transport inducibility were more sensitive to Cr(VI) in L. minor than in L. gibba. We also found fundamental differences in quantum yield of regulated, Y(NPQ), and nonregulated, Y(NO), non-photochemical quenching between the two species. As Cr(VI) concentration increased in the growth medium, L. minor responded with considerable increase of Y(NPQ) with a parallel significant increase of Y(NO). By contrast, in L. gibba only 200 μM Cr(VI) in the growth medium resulted in elevation of Y(NPQ) while Y(NO) remained more or less constant within the regarding Cr(VI) concentration range during 48 h. Photosynthetic pigment content did not change considerably during the short-term Cr(VI) treatment but decrease of Chl a/b and increase of Car/Chl ratios were observed in good accordance with the changes in Chl fluorescence parameters. The data suggest that various duckweed species respond with different sensitivity to the same ambient concentrations of Cr(VI) in the growth medium, and presumably to other environmental stresses too, which may have an influence on their competitive relations when heavy metal pollution occurs in aquatic ecosystem. and V. Oláh ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2297. Short-term dynamics of stomatal response to sudden increase in CO2 concentration in maize supplied with different amounts of water

Creator:
Hladnik, J., Eler, K., Kržan, K., Pintar, M., and Vodnik, D.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
curve fitting, elevated CO2, stomatal dynamics, water potential, water vapour pressure deficit, and Zea mays
Language:
Multiple languages
Description:
Environmental factors that influence stomatal conductance (gs) interact through a complex network of signal transduction and have therefore highly interdependent effect. In the present study we examined how plant water status affects stomatal sensitivity to the change of CO2 concentration ([CO2]). We investigated the short-term dynamic of stomatal response to a sudden [CO2] increase (from 400 to 700 µmol(CO2) mol-1) in maize supplied with different amounts of water (resulting ψw = -0.35, -0.52 and -0.75 MPa). Gas exchange measurements were performed in short logging intervals and the response was monitored under two different levels of water vapour pressure deficit (VPD) of 1 and 2 kPa in order to observe the impact of air humidity. Generalized logistic curves were fitted to standardized stomatal response data, which enabled us to objectively estimate the level (relative decrease of g s) and the dynamics of the response. Soil water stress and high VPD significantly decreased relative stomatal closure in response to [CO2] rise, but simultaneously accelerated stomatal response to [CO2], as revealed by shorter half life (t1/2). VPD significantly affected the response of well-watered plants. In contrast, a fast stomatal reaction of water-deprived plants was predetermined by a low xylem water potential (ψw) of the leaf and the influence of air humidity was minor. and J. Hladnik ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2298. Short-term effects of extensive fertilization on community composition and carbon uptake in a Pannonian loess grassland

Creator:
Czóbel, Sz., Németh, Z., Szirmai, O., Gyuricza, Cs., Tóth, A., Házi, J., Vikár, D., and Penksza, K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
fotosyntéza, photosynthesis, canopy chamber, in situ experiment, net ecosystem CO2 exchange, nutrient treatment, species composition, 2, and 581
Language:
Multiple languages
Description:
Among the most extended ecosystems of the temperate zone, the seminatural, dry grasslands constitute a substantial proportion in the Carpathian Basin. The aim of our present study was to investigate the short-term effect of extensive fertilization on the species composition and CO2 exchange of loess grassland at community level. The in situ investigation of the latter parameter have not been yet carried out in Pannonian loess grasslands. Most of the parameters studied showed a considerable interannual variation both in the fertilized and in the control stands. As a result of the treatment, the average species number of the fertilized stand decreased by 22%, which was more significant in the autumn (26%) than in the spring. Diversity values, including Shannon index and species richness, increased by nearly 1.5 times in the year with adequate rainfall compared with the initial values. In general, species richness and the ratio of dicots decreased, while the ratio of therophytes, alien competitors, and C4 plants increased with the addition of fertilizers. Significant carbon sequestration potential was only detected during wet periods in the fertilized grass. The rate of CO2 uptake was found to be nearly five times higher in the fertilized stand and nearly three times higher in the control stand during the wet year compared with the previous, extremely dry year. The CO2 uptake potential of the fertilized grassland exceeded that of the control stand by 12% in the year with high rainfall, while the rate of CO2 exchange dropped by 50% in the dry year in the fertilized stand. Our study reinforced the idea that the decline in species richness was not necessarily followed by the reduction of stand level carbon uptake in a short period due to an insignificant change in ecophysiological functional groups. and S. Z. Czóbel ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2299. Short-term effects of surface dust: alleviating photoinhibition of cotton under high irradiance in the Tarim Basin

Creator:
Li, L. and Mu, G.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
chlorofyl, chlorophyll, chlorophyll a fluorescence, dust retention, electron transport, photosynthetic rate, 2, and 581
Language:
Multiple languages
Description:
Dust deposition on leaf surfaces can impact the growth and physiological traits of plants. We carried out a field experiment to investigate short-term effects of light surface dust on photosynthesis of cotton in the Tarim Basin using chlorophyll fluorescence and gas-exchange techniques. JIP-test analysis of OJIP curves showed that the total performance index for leaves without dust decreased by 32% at noon compared to the morning value. High irradiance at noon reduced actual quantum yield of PSII and increased nonphotochemical quenching for leaves without dust, showing photoinhibition. It suggested that light surface dust alleviated photoinhibition of cotton to high irradiance on a short-term basis. For the leaves without dust, high irradiance induced photoinhibition not only with respect to the photochemistry reactions but the biochemical pathways of CO2 fixation. Mechanisms such as thermal dissipation and enhanced electron flux to PSI protected the photosynthetic apparatus under high irradiance., L. Li, G. Mu., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2300. Short-term responses of photosynthetic membrane lipids and photochemical efficiency in plants of Phaseolus vulgaris and Vigna unguiculata submitted to high irradiance

Creator:
Ferreira, L. C. S., Bressan-Smith, R., Elias, T. F., Silva, F. F., Viana, L. H., and Oliveira, J. G.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll a fluorescence, cultivar differences, French bean, lipid peroxidation, photoinhibition, photosynthesis, and species differences
Language:
Multiple languages
Description:
Primary leaves of young plants of common bean (Phaseolus vulgaris cv. Carioca and Negro Huasteco) and cowpea (Vigna unguiculata Walp cv. Epace 10) were exposed to high irradiance (HI) of 2 000 µmol m-2 s-1 for 10, 20, and 30 min. The initial fluorescence (F0) was nearly constant in response to HI in each genotype except for Carioca. A distinct reduction of maximum fluorescence (Fm) was clearly observed in stressed genotypes of beans after 20 min followed by a slight recovery for the longer stress times. In common bean, the maximum quantum yield (Fv/Fm) was reduced slowly from 10 to 30 min of HI. In cowpea, only a slight reduction of Fv/Fm was observed at 20 min followed by recovery to normal values at 30 min. HI resulted in changes in the photochemical (qP) and non-photochemical (qN) quenching in both species, but to a different extent. In cowpea plants, more efficiency in the use of the absorbed energy under photoinhibitory conditions was related to increase in qP and decrease in qN. In addition, lipid peroxidation changed significantly in common bean genotypes with an evident increase after 20 min of HI. Hence the photosynthetic apparatus of cowpea was more tolerant to HI than that of common bean and the integrity of cowpea cell membranes was apparently maintained under HI. and L. C. S. Ferreira ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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