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.
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
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
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.].
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.
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.
Hindlimb unweighting (HU) leads to capillary regression in skeletal muscle. However, the molecular mechanism(s) remains to be elucidated. To gain insight into the regulation of this process, we investigated gene expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), angiopoietin, and their receptors in the atrophied muscle induced by HU. The hindlimbs of mice were unweighted by tail-suspension and then the gastrocnemius muscles were isolated after 10 days. To assess the capillary distribution, the capillary endothelium in frozen transverse sections was identified by staining for alkaline phosphatase. The mRNA levels were analyzed using a real-time reverse transcription-polymerase chain reaction. After 10 days of HU, the number of capillaries around a muscle fiber was significantly decreased by 19.5 %, suggesting that capillary regression appears to occur. The expression of HIF-1α was significantly down-regulated after 10 days of HU. The expression of VEGF remained unchanged, whereas those of Flt-1, KDR/Flk-1, and neuropilin-1 were significantly down-regulated, suggesting that VEGF signaling through these receptors would be attenuated. The expression of angiopoietin-1, and -2, as well as their receptor, Tie-2 were also significantly down-regulated, suggesting that angiopoietin-1 signaling through Tie-2 would be attenuated. These findings suggest that alterations in expression of VEGF, angiopoietins, and their receptors may be associated with capillary regression after HU., A. Wagatsuma., and Obsahuje biblografii a bibliografické odkazy
Several neurodegenerative conditions, such as Alzheimer’s disease and Parkinson’s disease, or vascular dementia and cognitive impairment, are associated with mild hyperhomocysteinemia. Hyperhomocysteinemia is defined as an increas e of the homocysteine (Hcy) level beyond 10 μM. Although the adverse effect of Hcy on neurons is well documented, knowledge about the impact of this amino acid on glial cells is missing. Therefore, with the aim to evaluate the neurotoxic properties of Hcy on glial cells, we used a glioblastoma cell line as a study model. The viability of cells was assayed biochemically and cytologically. At a concentration around 50 μM in the culture medium D,L -Hcy induced cell death. It is noteworthy that Hcy induces cell death of human glial cells at concentrations encountered during mild hyperhomocysteinemia. Therefore, we propose that Hcy -induced impairment of neuronal functions along with damage of glial cells may contribute to the etiopathogenesis of neurodegenerative diseases associated with hyperhomocysteinemia., H. Škovierová, S. Mahmood, E. Blahovcová, J. Hatok, J. Lehotský, R. Murín., and Obsahuje bibliografii
Age of host eggs can be a limiting factor for egg parasitoids. It is expected that old eggs are less preferred by egg parasitoids, which can discriminate between eggs of different ages by using chemical cues. The objective of this study was to determine the preference, development and arrestment of Telenomus remus Nixon (Hymenoptera: Scelionidae) parasitizing Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) eggs of different ages. This egg parasitoid preferred to parasitize 1- and 2-day-old eggs rather than 3-day-old eggs in choice and no-choice assays. However, although the percentage emergence of parasitoids is significantly lower from 2- and 3-day-old eggs, the sex ratio and developmental time are unaffected. Parasitoids spent longer searching substrates impregnated with extracts of 1- and 2-day old eggs than 3-day-old eggs. Our results reveal that T. remus is able to distinguish the most suitable (1-day-old) from the least suitable (3-day-old) host eggs, but unable to recognize the unsuitability of intermediate aged eggs. Egg arrestants may be responsible for the preference of T. remus for ovipositing in 1- and 2-day old eggs., Maria Fernanda Gomes Villalba Penaflor ... [et al.]., and Obsahuje seznam literatury