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The net photosynthetic rate (PN), the sample room CO₂ concentration (CO₂S) and the intercellular CO₂ concentration (Ci) in response to PAR, of C3 (wheat and bean) and C4 (maize and three-colored amaranth) plants were measured. Results showed that photorespiration (Rp) of wheat and bean could not occur at 2 % O₂. At 2 % O₂ and 0 µmol mol-1 CO₂, PN can be used to estimate the rate of mitochondrial respiration in the light (Rd). The Rd decreased with increasing PAR, and ranged between 3.20 and 2.09 µmol CO₂ m⁻² s⁻¹ in wheat. The trend was similar for bean (between 2.95 and 1.70 µmol CO₂ m⁻² s⁻¹), maize (between 2.27 and 0.62 µmol CO₂ m⁻² s⁻¹) and three-colored amaranth (between 1.37 and 0.49 µmol CO₂ m⁻² s⁻¹). The widely observed phenomenon of Rd being lower than Rn can be attributed to refixation, rather than light inhibition. For all plants tested, CO₂ recovery rates increased with increasing light intensity from 32 to 55 % (wheat), 29 to 59 % (bean), 54 to 87 % (maize) and 72 to 90 % (three-colored amaranth) at 50 and 2,000 µmol m⁻² s⁻¹, respectively.
UV exposure is harmful to plants. Increasing resistance against UV light is thus of great importance to their growth. Para-Aminobenzoic acid (PABA) has major roles in many biological processes, involving nucleotide biosynthesis, DNA repair, and DNA methylation, which contributed to UV irradiation. However, no study reports the effect of PABA on UV tolerance, or details of the underlying molecular mechanisms are explored. Hence, the objective of the research is to study the protective effect of PABA on UV in Arabidopsis and explored the molecular mechanisms. We overexpressed PABA synthase gene (Pabs) from Mushroom Agaricus bisporus in Arabidopsis and observed reduced root growth and UV-C hyposensitivity exposed to 2500 J m⁻² UV-C light. UV-C-induced DNA damage was significantly reduced and the expression of decreased DNA methylation 1 (DDM1) was remarkably higher in the Pabs lines, suggesting that overexpression of Pabs may protect against UV-induced DNA damage. In addition, overexpression of Pabs leads to an elevated reactive oxygen species production at root tips and enhanced catalase and superoxide dismutase activity, which may correlate with the enhanced UV tolerance of the Pabs overexpression lines. In summary, overexpression of Pabs from A. bisporus enhances UV-C tolerance of Arabidopsis, suggesting that Pabs takes an important part in defence against DNA damage.
We have recently shown that synaptic Ca2+-impearmable AMPA receptors (AMPARs) internalization in dorsal horn neurons underlies the maintenance of nociceptive hypersensitivity in infl ammatory pain. Here we have analyzed if traffi cking of extrasynaptic AMPARs is also changed during development and maintenance of persistent pain. We report that Complete Freund’s Adjuvant (CFA)-induced infl ammation causes an increase in functional expression of extrasynaptic AMPARs in rat substantia gelatinosa (SG) neurons during the maintenance rather than development of persistent pain. This increase, revealed as a signifi cant enhancement of AMPA-induced membrane currents and [Ca2+]i transients, was observed only in neurons characterized by an intrinsic tonic fi ring properties whereas no changes were observed in neurons exhibiting a strong adaptation. The increase was also accompanied by an enhancement of surface GluR1 expression and of the total amount of cobalt-positive neurons indicating an increase in a pool of GluR2-lacking AMPARs in extrasynaptic plasma membrane. These results suggest that functional changes in extrasynaptic AMPARs of tonic SG neurons that are associated with the maintenance of nociceptive hypersensitivity may also contribute to infl ammatory pain. We also suppose that there is a different contribution of tonic and transient neurons to the detection of peripheral painful stimuli and to maintenance of nociceptive hypersensitivity.
To investigate the contamination levels of heavy metals, surface water and sediment samples were collected from 21 sites along the Gan River. The heavy metal concentrations (V, Co, Cr, Ni, Cu, Zn, Cd, and Pb) were determined using inductively coupled plasma spectrometry (ICP-MS). The results demonstrated that the status of the surface water and sediments as a whole were relatively clean with regard to heavy metals (except for Cd) compared to water quality standards and sediment quality guidelines. The two heavy metal sources of the surface water and sediments were identified separately using factor analysis (FA). High levels of metals were found in the sediment in the upstream and downstream due to frequent mining and industrial activities, whereas concentrations of heavy metal in the surface water from two sources were abundant in the upstream and midstream – likely related to mining activities and sediment suspension. As indicated by enrichment factor (EF) and potential ecological risk index (PERI), Zn, Pb, and Cd were the most anthropogenically enriched metals, while sediments in the upstream and downstream had high potential ecological risk. Local people, including adults and children who ingested water from the Gan River, showed little potential non-carcinogenic risk, as the hazard index (HI) scores were less than 1. Compared with those in other rivers in the world, heavy metal enrichments in surface water and sediments were of moderate levels.
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