Number of results to display per page
Search Results
902. Effect of high irradiance and high temperature on chloroplast composition and structure of Dioscorea zingiberensis
- Creator:
- Liao, F. Y., Li, H. M., and He, P.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carotenoids, chlorophylls, fany acids, lipids, and recovery
- Language:
- Multiple languages
- Description:
- High irradiance (HI) and high temperature (HT) increased in chloroplasts the content of monogalactosyldiacylglycerol (MGDG) and decreased the contents of digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylinositol (PI). HI and HT accelerated the transformation of DGDG to MGDG. The contents of unsaturated fatty acids in chloroplasts increased, while those of saturated fatty acids decreased. The contents of total carotenoids, neoxanthin, violaxanthin, lutein, and β-carotene increased first, then decreased. The content of chlorophyll decreased. HI caused the unfolding of thylakoids that was not resumed after a 72-h recovery. and F. Y. Liao, H. M. Li, P. He.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
903. Effect of high light intensity on photoinhibition, oxyradicals and artemisinin content in Artemisia annua L.
- Creator:
- Poulson, M. E. and Thai, T.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, chlorophyll fluorescence, environmental stress, irradiation, 2, and 581
- Language:
- Multiple languages
- Description:
- a1_Artemisia annua L. produces a compound called artemisinin that is a potent anti-malarial compound. However concentration of artemisinin within the plant is typically low (less than 0.8% of dry mass) and currently supply of the drug by the plant does not meet world demand. This investigation was carried out to determine whether high intensity light treatment would increase production of artemisinin in leaves of A. annua. Photoinhibition (14%) was induced in leaves of A. annua when they were subjected to 6 h of high-intensity light [2,000 μmol(photon) m-2 s-1]. Maximum photochemical efficiency of PSII showed a recovery of up to 95% within 24 h of light induced inhibition. During the light treatment, photochemical efficiency of PSII in leaves of the high-intensity light-treated plants was 38% lower than for those from leaves of plants subjected to a low-intensity-light treatment of 100 μmol(photon) m-2 s-1. Nonphotochemical quenching of excess excitation energy was 2.7 times higher for leaves treated with high-intensity light than for those irradiated with low-intensity light. Elevation in oxidative stress in irradiated leaves increased presence of reactive oxygen species (ROS) including singlet oxygen, superoxide anions, and hydrogen peroxide. Importantly, the concentration of artemisinin in leaves was two-fold higher for leaves treated with high-intensity light, as compared to those treated with low-intensity light. These results indicate that A. annua responds to high irradiance through nonphotochemical dissipation of light energy yet is subject to photoinhibitory loss of photosynthetic capacity. It can be concluded that A. annua is capable of rapid recovery from photoinhibition caused by high light intensity., a2_High light intensity also induced oxidative stress characterized by increased concentration of ROS which enhanced the content of artemisinin. Such a light treatment may be useful for the purpose of increasing artemisinin content in A. annua prior to harvest., M. E. Poulson, T. Thai., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
904. Effect of high light intensity on the photosynthetic apparatus of two hybrid lines of Paulownia grown on soils with different salinity
- Creator:
- Stefanov, M., Yotsova, E., Markovska, Y., and Apostolova, E. L.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- listy, citlivost na světlo, fotoinhibice, rychlostní konstanta, tolerance soli, leafs, light sensitivity, photoinhibition, rate constant, salt tolerance, 2, and 581
- Language:
- Multiple languages
- Description:
- The objective of this investigation was to evaluate the simultaneous action of light stress and salinity. Pulse amplitude modulated chlorophyll fluorescence, P700 redox state, and pigment analysis were used to assess the impact of high light intensity on Paulownia tomentosa × fortunei and Paulownia elongata × elongata grown on soils with different salinity. It was found that light stress reduced the amount of pigments and the efficiency of photochemical energy conversion, inhibited the maximum and the effective quantum yields of PSII photochemistry, decreased photochemical quenching and photosynthetic rate. Data also showed influence on the primary quinone acceptor (QA) reoxidation, which led to the restriction of the electron flow from QA to plastoquinone and stimulation of the cyclic electron flow. The possible reasons for the increased effects of the light stress under conditions of high salt concentration in soil for Paulownia tomentosa × fortunei are discussed., M. Stefanov, E. Yotsova, Y. Markovska, E. L. Apostolova., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
905. Effect of high temperature on dehydration-induced alterations in photosynthetic characteristics of the resurrection plant Haberlea rhodopensis
- Creator:
- Velitchkova, M., Doltchinkova, V., Lazarova, D., Mihailova, G., Doncheva, S., and Georgieva, K.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, desiccation, thylakoid membranes, 2, and 581
- Language:
- Multiple languages
- Description:
- The effect of high temperature (HT) and dehydration on the activity of photosynthetic apparatus and its ability to restore membrane properties, oxygen evolution, and energy distribution upon rehydration were investigated in a resurrection plant, Haberlea rhodopensis. Plants growing under low irradiance in their natural habitat were desiccated to air-dry state at a similar light intensity [about 30 μol(photon) m-2 s-1] under optimal day/night (23/20°C) or high (38/30°C) temperature. Our results showed that HT alone reduced the photosynthetic activity and desiccation of plants at 38°C and it had more detrimental effect compared with desiccation at 23°C. The study on isolated thylakoids demonstrated increased distribution of excitation energy to PSI as a result of the HT treatment, which was enhanced upon the desiccation. It could be related to partial destacking of thylakoid membranes, which was confirmed by electron microscopy data. In addition, the surface charge density of thylakoid membranes isolated from plants desiccated at 38°C was higher in comparison with those at 23°C, which was in agreement with the decreased membrane stacking. Dehydration led to a decrease of amplitudes of oxygen yields and to a loss of the oscillation pattern. Following rehydration, the recovery of CO2 assimilation and fluorescence properties were better when desiccation was performed at optimal temperature compared to high temperature. Rehydration resulted in partial recovery of the amplitudes of flash oxygen yields as well as of population of S0 state in plants desiccated at 23°C. However, it was not observed in plants dehydrated at 38°C. and M. Velitchkova ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
906. Effect of high temperature on photosynthesis and transpiration of sweet corn (Zea mays L. var. rugosa)
- Creator:
- Ben-Asher, J., Garcia y Garcia, A., and Hoogenboom, G.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- maize, quasi stem conductance, transpiration rate, vapor pressure deficit, and water use efficiency
- Language:
- Multiple languages
- Description:
- Four temperature treatments were studied in the climate controlled growth chambers of the Georgia Envirotron: 25/20, 30/25, 35/30, and 40/35 °C during 14/10 h light/dark cycle. For the first growth stage (V3-5), the highest net photosynthetic rate (PN) of sweet corn was found for the lowest temperature of 28-34 µmol m-2 s-1 while the PN for the highest temperature treatment was 50-60 % lower. We detected a gradual decline of about 1 P N unit per 1 °C increase in temperature. Maximum transpiration rate (E) fluctuated between 0.36 and 0.54 mm h-1 (≈5.0-6.5 mm d-1) for the high temperature treatment and the minimum E fluctuated between 0.25 and 0.36 mm h-1 (≈3.5-5.0 mm d-1) for the low temperature treatment. Cumulative CO2 fixation of the 40/35 °C treatment was 33.7 g m-2 d-1 and it increased by about 50 % as temperature declined. The corresponding water use efficiency (WUE) decreased from 14 to 5 g(CO2) kg-1(H2O) for the lowest and highest temperature treatments, respectively. Three main factors affected WUE, PN, and E of Zea: the high temperature which reduced PN, vapor pressure deficit (VPD) that was directly related to E but did not affect PN, and quasi stem conductance (QC) that was directly related to PN but did not affect E. As a result, WUE of the 25/20 °C temperature treatment was almost three times larger than that of 40/35 °C temperature treatment. and J. Ben-Asher, A. Garcia y Garcia, G. Hoogenboom.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
907. Effect of high temperature on photosynthetic electron transport activities of the cyanobacterium Spirulina platensis
- Creator:
- Venkataramanaiah, V., Sudhir, P., and Murthy, S. D. S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, energy transfer, fluorescence emission spectra, and photosystems 1 and 2
- Language:
- Multiple languages
- Description:
- The activities of photosystem 2 (PS2) and whole chain electron transport declined in high temperature treated cells at the room temperature beyond 35 °C, while photosystem 1 (PS1) showed increased activity. Thylakoid membrane studies did not exhibit increase in PS1 activity indicating that the enhancement of PS1 activity is due to permeability change of cell membranes. However, the electron transport activity measured from reduced duroquinone to methylviologen which involves intersystem electron transport was extremely sensitive to high temperature. The activity of PS2 at different irradiance, which was accompanied by alterations in absorption and fluorescence emission properties, indicated changes in the energy transfer processes within phycobilisomes. Thus high temperature has multiple target sites in photosynthetic electron transport system of Spirulina platensis. and V. Venkataramanaiah, P. Sudhir, S. D. S. Murthy.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
908. Effect of hypoxia and post-hypoxia on the fluctuations in contents of malate and citrate, the activity of malic enzyme, and on the intensity of gas exchange in moss gametophores
- Creator:
- Rut, G., Rzepka, A., and Krupa, J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, calcium, malate, Mnium, photosynthesis, Polytrichum, post-hypoxia, and respiration
- Language:
- Multiple languages
- Description:
- Mosses are plants of simple anatomical structure and as they occur in habitats characterised not only by major changes in the concentrations of carbon dioxide, they suffer the stress of periodic water shortages or submergence in water. The condition of hypoxia (submergence in water or CaCl2 solution) prompted the increase in daily fluctuations in malate content, particularly in the gametophores of Polytrichum piliferum Hedw. No significant increases in daily fluctuations of citrate were found in the hypoxia and post-hypoxia conditions. Placing gametophores for 168 h in air with a concentration of CO2 at ∼ 350 μmol mol-1, and 21% of oxygen, after being submerged for 24 h in water, reduced the daily fluctuations of malate and citrate. Keeping the plants in these conditions for a long time (120-168 h) produced the increase in photosynthesis intensity in the gametophores of Mnium undulatum Hedw. and P. piliferum by 13% and 51%, respectively, when compared with plants submerged for 24 h. The intensity of respiration during post-hypoxia, however, was markedly lower compared with the intensity of the process recorded in hypoxia, particularly in the gametophores of P. piliferum. The increased daily fluctuations of malate and NAD(P)H in the studied species under hypoxia could constitute an important element of adaptive strategy to these conditions. and G. Rut, A. Rzepka, J. Krupa.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
909. Effect of imazapic residues on photosynthetic traits and chlorophyll fluorescence of maize seedlings
- Creator:
- Su, W. C., Sun, L. L., Wu, R. H., Ma, Y. H., Wang, H. L., Xu, H. L., Yan, Z. L., and Lu, C. T.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fluorescence chlorofylu, výměna plynu, růstové charakteristiky, fotosystém II, chlorophyll fluorescence, gas exchange, growth characteristics, photosystem II, 2, and 581
- Language:
- Multiple languages
- Description:
- The influence of various concentrations of imazapic residues (0-800 μg kg-1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection., W. C. Su, L. L. Sun, R. H. Wu, Y. H. Ma, H. L. Wang, H. L. Xu, Z. L. Yan, C. T. Lu., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
910. Effect of indol-3-yl acetic acid on photosynthetic characteristics of wheat flag leaf during grain filling
- Creator:
- Aldesuquy, H. S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carotenoids, chlorophylls, 14CO2 assimilation, flag leaf, fresh and dry masses, Hill reaction, leaf area, photosynthates, polysaccharides, proteins, and sugars
- Language:
- Multiple languages
- Description:
- Area and fresh and dry masses of flag leaf show two phases of development during grain filling in Triticum aestivum. The initial large increase in leaf size is mainly due to water intake. Contents of chlorophylls and carotenoids, reducing sugars, and sucrose, Hill reaction rate, and photosynthetic activity increased during leaf growth, but a noticeable decline in these parameters followed throughout leaf senescence. The maximum accumulation of polysaccharides and proteins occurred at the beginning of grain set, but a continuous decline in their absolute values was manifested during grain filling. Grain priming with indol-3-yl acetic acid (IAA) at 25 mg kg-1 stimulated the flag leaf growth, namely its fresh and dry masses and its area. Furthermore, the stimulatory effect was mainly due to the increase in the pigment formation that in turn increased the photosynthetic activity of flag leaf during grain filling. On the other hand, the highest dose of IAA (50 mg kg-1) attenuated the growth and physiological activity of flag leaf through its inhibitory action on leaf fresh and dry masses, leaf area, pigments, saccharides and protein formation, as well as its effect on 14CO2 assimilation.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public