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412. Chain correlation between variables of gas exchange and yield potential in different winter wheat cultivars
- Creator:
- Jiang, G. M., Hao, N. B., Bai, K. Z., Zhang, Q. D., Sun, J. Z., Guo, R. J., Ge, Q. Y., and Kuang, T. Y.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- apparent quantum yield of CO2 fixation, compensation irradiance, cultivars with high and low yield potentials, dark respiration, flag leaf, net photosynthetic rate, stomatal conductance, transpiration, and water use efficiency
- Language:
- Multiple languages
- Description:
- Variables of gas exchange of flag leaves and grain yield potentials of five representative winter wheat (Triticum aestivum L.) cultivars varied greatly across different development stages under the same management and irrigation. The cultivars with high yield potential had higher net photosynthetic rate (PN), PPFD (photosynthetic photon flux density) saturated photosynthetic rate (Psat), stomatal conductance (gs), and maximum apparent quantum yield of CO2 fixation (Φm,app) than those with low grain yield, but their dark respiration rate (RD) and compensation irradiance (Ic) were remarkably lower. Compared with overall increase of yield potential of 71 % from low yield cultivars to high yield ones, PN, Psat, Φm,app, and gs were 13, 19, 57, and 32 % higher, respectively; but RD and Ic decreased by 19 and 76 %, respectively. Such difference was evidently large during anthesis stage (e.g., PN by 33 %), which indicated that this period could be the best for assisting further selection for better cultivars. However, transpiration rate (E) and water use efficiency (WUE) differed only little. At different development stages, especially at anthesis, PN and Psat were positively correlated with Φm,app, gs, and yield potential, and negatively correlated with RD and Ic. Thus the high-yield-potential winter wheat cultivars possess many better characters in photosynthesis and associated parameters than the low-yield cultivars. and G. M. Jiang ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
413. Chamber response time: A neglected issue in gas exchange measurements
- Creator:
- Weiss, I., Mizrahi, Y., and Raveh, E.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chamber steady state, Hylocereus, infrared gas analyser, laboratory-made chambers, net CO2 uptake, open system, and self-clamping chambers
- Language:
- Multiple languages
- Description:
- When the dimensions of standard commercial chambers for measuring gas exchange cannot accommodate the object being measured, scientists construct their own chambers. The time needed to reach chamber steady state (chamber response time) depends on net system volume (e.g. chamber and tubing volume) and airflow. Unfortunately, some authors take chamber response time into consideration while others ignore it. We present the formula for calculating chamber response time. and I. Weiss, Y. Mizrahi, E. Raveh.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
414. Chamber series and space-scale analysis of CO2 gas-exchange in grassland vegetation: A novel approach
- Creator:
- Czóbel, Sz., Fóti , Sz., Balogh, J., Nagy, Z., Bartha, S., and Tuba, Z.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- canopy chamber, grassland, loess, sand, and stand CO2 measurements
- Language:
- Multiple languages
- Description:
- Significant part of our work was developing a new type of CO2 and H2O gas exchange chambers fit for measuring stand patches. Ground areas of six chambers (ranged between 0.044-4.531 m2) constituted a logarithmic series with doubling diameters from 7.5 to 240.0 cm. We demonstrate one of the first results for stand net ecosystem CO2 exchange (NEE) rates and temporal variability for two characteristic Central European grassland types: loess and sand. The measured mean NEE rates and their ranges in these grasslands were similar to values reported in other studies on temperate grasslands. We also dealt with the spatial scale dependence from ecophysiological point of view. Our chamber-series measurement was performed in a perennial ruderal weed association. The variability of CO2-assimilation of this weed vegetation showed clear spatial scale-dependence. We found the lowest variability of the vegetation photosynthesis at the small-middle scales. The results of spatial variability suggest the 0.2832 m2 patch size is the characteristic unit of the investigated weed association and there is a kind of synphysiological minimi-area with characteristic size for each vegetation type. and Sz. Czóbel ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
415. Changes in biomass, chlorophyll content and gas exchange of beans and peppers under nitrogen and water stress
- Creator:
- Peňuelas, J., Biel, C., and Estiarte, M.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- We experimentally produced moderate water stress that reduced leaf, stem, root and fruit biomass of peppers, and severe nitrogen (N) limitations that almost stopped their development. Root/shoot ratios (R/S) were higher in N-limited plants. Low water availability (and also low N availability) produced lower stomatal conductance (g,). Specific leaf mass was higher and chlorophyll (Chl) concentration was lower under low N-availability. The same experimental conditions produced smaller differences among treatments in beans (with N-fixing symbionts). Water stress increased its relative importance as shown by the induced increase in root/shoot ratio. N stress was less important as shown by the absence of effects on Chl concentrations and g^. Both peppers and beans responded to limited availability of nitrogen and water by allocating to structures involved in uptake (roots), by longer organ duration, and by increasing the efficiency of N and water use.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
416. Changes in chlorophyll a and b contents and acivities of photosystems 1 and 2 in rice seedlings induced by NaCl
- Creator:
- Singh, A.K. and Dubey, R.S.
- Format:
- Type:
- model:internalpart and TEXT
- Subject:
- carotenoids, fluorescence, Hill reaction, Oryza sativa L., photosynthesis, plant age, salinity, and salt tolerance.
- Language:
- Multiple languages
- Description:
- During a 5-20 d growth at moderate salinity (7 dS m‘i) in rice seedlings of salt sensitive cultivars Ratna and Jaya a larger decrease in chlorophyll (Chl) a and b contents was observed than in tolerant cvs. CSR-1 and CSR-3. At higher salinity (14 dS m'i) about 40 % declines in both whole chain electron transport and photosystem (PS) 2 activities were observed in the tolerant cvs. and about 62 to 67 % declines in the sensitive ones. No apparent change in PSI activity was observed due to salinization in the both sets of cultivars. Higher rate of Hill reaction was observed in chloroplasts ffom salt stressed seedlings of tolerant cultivars whereas inhibition in this activity was found in the sensitive ones. Chloroplasts isolated from stressed seedlings of sensitive cultivars showed about 31 % reduction in fluorescence emission at 685 nm as well as a major decrease in absorption with shifts in peaks in the visible region of spectrum. Thus salt sensitivity in rice is associated with decreased contents of Chls and carotenoids, PS2 and Hill reaction activities, and fluorescence emission.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
417. Changes in chlorophyll a fluorescence, lipid peroxidation, and detoxificant system in potato plants grown under filtered and non-filtered air in open-top chambers
- Creator:
- Calatayud, A., Alvarado, J. W., and Barreno, E.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- antioxidant enzymes, ascorbate, lipid peroxidation, non-photochemical quenching, ozone, photochemical quenching, and Solanum tuberosum
- Language:
- Multiple languages
- Description:
- Its high oxidant capacity and ability to generate reactive oxygen species cause ozone toxicity. We studied the effect of ambient ozone on chlorophyll (Chl) a fluorescence, antioxidant enzymes, ascorbate contents, and lipid peroxidation in potatoes grown in open-top chambers in the field. In plants grown in non-filtered air (NFA), the development of non-photochemical quenching brought about a decrease in photosystem 2 (PS2) photochemical efficiency. Also the ability of PS2 to reduce the primary acceptor QA was lower than in charcoal-filtered, ozone-free air (CFA). Changes in Chl fluorescence yield were associated with changes in the thylakoid membrane. Ozone altered chloroplast membrane properties, as indicated by an increase in membrane lipid peroxidation in FNA-leaves compared to CFA plants. The ascorbate pool and activities of antioxidant enzymes were used for an indication of the detoxification system state in NFA and CFA leaves, whereby ozone affects the ascorbate concentration and decreases the antioxidant enzymes activities. The capacity of both detoxifying systems together was not high enough to protect potato plants against ambient ozone concentrations which reduced the photosynthetic yield in this potato cultivar. and A. Calatayud, J. W. Alvarado, E. Barreno.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
418. Changes in chlorophyll content, photosynthetic rate and saccharides level in developing Rhizophora hypocotyls
- Creator:
- Gunasekar, M.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- In the hypocotyls of Rhizophora mucronata Lamk. and R. apiculata Bl. during viviparous germination the concentrations of chlorophyll (Chl) and total sugars, and net photosynthetic rate (P^) were increased quadratically, while linear relationship existed between starch content and the developmental phase. R. apicuiata hypocotyls had a higher value of as well as higher Chl, sugar and starch contents than hypocotyls of R. mucronata.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
419. Changes in chlorophyll fluorescence and photosynthetic activity of French bean leaves induced by gamma radiation
- Creator:
- Saakov, V., Lang, M., Schindler, C., Stober, F., and Lichtenthaler, H. K.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- When exposed to Y-radiation (12, 8 and 3.5 kGy), the growth of beán seedlings {Phaseolus vulgaris L.) was stopped and after some hours or days the plants began to wilt in a dose-dependent manner, starting from the leaf rim. The rate of the dark respiration {R) of leaves increased and that of net photosynthesis {P^ was strongly reduced. The regulation of stomata opening and closure was lost and the stomatal conductance (g^) of the y-ray exposed plants was strongly reduced. The reduced was only partly due to either the partial or almost Ml stomata closure. Chlorophyll (Chl) fluorescence measurements with a two-wavelength fluorometer and a PAM fluorometer showed an increasingly reduced variable fluorescence Fy, lower values of Rfj, of ground fluorescence Fq, and of the fluorescence ratios Fy/F,n and Fy/F^. This indicated a damage to the photosynthetic apparatus. The increasing loss of photosynthetic pigments in the 350 krad exposed plants was also detected via an increase in the fluorescence ratio F690/F730. The performance of the light driven xanthophyll cycle (violaxanthin/zeaxanthin transformation) proceeded in the y-ray treated plants only at reduced rates. The y-ray damage of plants can best be detected by measurements of stomatal conductance, and various Chl fluorescence ratios such as Rf(j, Fy/Fj, and Fy/F^,.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
420. Changes in chlorophyll fluorescence during the course of photoperiod and in response to drought in Casuarina equisetifolia Forst. and Forst.
- Creator:
- Martínez-Carrasco, R., Sánchez-Rodriguez, J., and Pérez, P.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- energy dissipation, photochemical and non-photochemical quenching, photosystem 2, quantum yield, and water stress
- Language:
- Multiple languages
- Description:
- The effects of drought and the diurnal changes in photosynthetic electron transport were studied in non-nodulated plants of Casuarina equisetifolia. The induction of fluorescence showed a slightly higher I step in water-stressed than control plants, and the time from the start of irradiation to the P step of induction was significantly shortened by drought. The quantum efficiency of photosystem 2 (PS2) in the dark-adapted state (Fv/Fm) was generally not affected by drought, whereas it decreased during the central hours of the day. The decrease in quantum yield of PS2 electron transport (Φ2) in water-stressed plants was associated with decreases in the photochemical efficiency of open (oxidised) PS2 centres (Fv'/Fm') and increases in non-photochemical quenching (qN) rather than with increased closure of PS2 centres (lowered photochemical quenching, qP). In contrast, the changes in quantum yield of electron transport during the day were related to changes in qP rather than in Fv'/Fm'. When chlorophyll fluorescence was measured at the same irradiance during the day, a greater qN was observed at the end of the drying cycle than after watering, and early and late in the photoperiod than in the central hours of the day. The greater qN at the beginning and end of the day did not prevent an increase in energy not used photochemically nor dissipated non-photochemically. Drought did not affect this excess of photon energy. and R. Martínez-Carrasco, J. Sánchez-Rodriguez, P. Pérez.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public