In a glasshouse, Bemisia tabaci infestation largely reduced response of photosynthesis to irradiance and CO2 concentration of Mikania micrantha compared with the non-infested control (C) ones. The maximum irradiance-saturated photosynthetic rate
(Pmax) and saturation irradiance (SI) of the infested M. micrantha were only 21.3 % and 6.5 % of the C-plants, respectively. B. tabaci infestation led to the reduction of contents of chlorophyll and carotenoids in M. micrantha, which was accompanied with the decrease of actual photosystem 2 (PS2) efficiency (ΦPS2), efficiency of excitation energy capture by open PS2 reaction centres (Fv'/Fm'), electron transport rate (ETR), and photochemical quenching (qP). Moreover, superoxide dismutase and catalase activities significantly decreased while proline and glutathione contents significantly increased in infested M. micrantha. Hence B. tabaci infestation not only induced direct damage of photosynthetic apparatus but also altered the antioxidant enzymes activities in M. micrantha, which might as consequences accelerate senescence of this weed. and L. L. Zhang, D. Z. Wen.
Physiological responses of two wheat (Triticum aestivum L.) genotypes (salt-tolerant DK961 and salt-sensitive JN17) to increased salt concentrations (50, 100, 150 mM NaCl: NaCl50, NaCl100, NaCl150) were studied. Photosynthetic capacity, irradiance response curves, contents of soluble sugars, proteins, and chlorophyll (Chl), K+/Na+ ratio, and activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in flag leaves were measured on 7 d after anthesis. In control (NaCl0) plants, non-significant (p>0.05) differences were found in gas exchange and saturation irradiance (SI) between salt-tolerant (ST) and salt-sensitive (SS) wheat genotypes. However, we found higher soluble sugar and protein contents, K+/Na+ ratio, and antioxidant enzyme activities, but lower Chl content and yield in ST wheat. Salinity stresses remarkably increased soluble sugar and protein contents and the antioxidant activities, but decreased K+/Na+ ratio, Chl contents, SI, photosynthetic capacities, and yield, the extent being considerably larger in JN17 than DK961. Although the soluble sugar and protein contents and the antioxidant activities of JN17 elevated more evidently under salt stresses, those variables never reached the high levels of DK961. The antioxidant enzyme activities of SS wheat increased in NaCl50 and NaCl100, but decreased rapidly when the NaCl concentration reached 150 mM. Thus the ST wheat could maintain higher grain yield than the SS one by remaining higher osmoregulation and antioxidative abilities, which led to higher photosynthetic capacity. Hence the ST wheat could harmonize the relationship between CO2 assimilation (source) and the grain yield (sink) under the experimental conditions. and Y. H. Zheng ... [et al.].
Changes in the activities of enzymes involved in scavenging active oxygen species were followed after exposing bean seedling leaves (Phaseolus vulgaris L.) to various cross stresses of irradiance and temperature. The activities of superoxide dismutase (SOD, EC 1.15.1.1) and ascorbate peroxidase (AsAPOD, EC 1.11.1.11) increased to different extent with prolonged irradiation of the leaves, and were stimulated by high temperature (HT). The activity of catalase (CAT, 1.11.1.6) decreased when exposed to strong irradiance (HI), and the decrease was further exacerbated when HI was combined with HT. CAT activity was more sensitive to HT than to HI. Ascorbate (AsA) content slightly decreased and then increased during the treatment of HI, but decreased under the cross stress of HI and HT. On the contrary, glutathione (GSH) content increased all the time during various treatments of irradiance and temperature. The increase in the combined stress was even more pronounced. Irradiance is the major reason in triggering the operation of xanthophyll cycle, which was difficult to be started by HT. The antioxidant systems tended to be inactivated with prolonged exposure to the cross stress of HI and HT. The de-expoxidated state of xanthophyll cycle, however, was increasing all the time, which indicated that the zeaxanthin-dependent thermal dissipation was one major energy dissipation pathway during the cross stress of HI and HT. and Liang Ye, Hui-yuan Gao, Qi Zou.
Microsporidia constitute a large group of obligate intracellular protozoan parasites that inject themselves into host cells via the extrusion apparatus of the infective spore stage. Although the injection process is poorly understood, its energy source is thought to reside in the posterior vacuole that swells significantly during spore firing. Here we report the presence and localisation of the key peroxisomal enzymes catalase and acyl-CoA oxidase (ACOX) within the posterior vacuole of Spraguea lophii (Doflein, 1898) spores. Western blot analyses show that these enzymes discharge out of the spore and end up in the medium external to the extruded sporoplasms. The presence of a catalase enzyme system in the Microsporidia was first made evident by the detection of significant levels of molecular oxygen in the medium containing discharging spores in the presence of hydrogen peroxide. Catalase was visualised in inactive, activated, and discharged spores using alkaline diaminobenzidine (DAB) on glutaraldehyde-fixed cells. The position of these enzymes within the extrusion apparatus before and during spore discharge support the Lom and Vávra model that postulates discharge occurs by an eversion process. In addition to these enzymes, spores of S. lophii contain another characteristic peroxisomal component, the very long chain fatty acid (VLCFA) nervonic acid. A sizeable decrease in nervonic acid levels occurs during and after spore discharge. These data indicate that nervonic acid is discharged from the spore into the external medium during firing along with the catalase and ACOX enzymes.
a1_Different parameters that vary during leaf development may be affected by light intensity. To study the influence of different light intensities on primary leaf senescence, sunflower (Helianthus annuus L.) plants were grown for 50 days under two photon flux density (PFD) conditions, namely high irradiance (HI) at 350 μmol(photon) m-2 s-1 and low irradiance (LI) at 125 μmol(photon) m-2 s-1. Plants grown under HI exhibited greater specific leaf mass referred to dry mass, leaf area and soluble protein at the beginning of the leaf development. This might have resulted from the increased CO2 fixation rate observed in HI plants, during early development of primary leaves. Chlorophyll a and b contents in HI plants were lower than in LI plants in young leaves. By contrast, the carotenoid content was significantly higher in HI plants. Glucose concentration increased with the leaf age in both treatments (HI and LI), while the starch content decreased sharply in HI plants, but only slightly in LI plants. Glucose contents were higher in HI plants than in LI plants; the differences were statistically significant (p<0.05) mainly at the beginning of the leaf senescence. On the other hand, starch contents were higher in HI plants than in LI plants, throughout the whole leaf development period. Nitrate reductase (NR) activity decreased with leaf ageing in both treatments. However, the NR activation state was higher during early leaf development and decreased more markedly in senescent leaves in plants grown under HI. GS activity also decreased during sunflower leaf ageing under both PFD conditions, but HI plants showed higher GS activities than LI plants. Aminating and deaminating activities of glutamate dehydrogenase (GDH) peaked at 50 days (senescent leaves). GDH deaminating activity increased 5-fold during the leaf development in HI plants, but only 2-fold in LI plants., a2_ The plants grown under HI exhibited considerable oxidative stress in vivo during the leaf senescence, as revealed by the substantial H2O2 accumulation and the sharply decrease in the antioxidant enzymes, catalase and ascorbate peroxidase, in comparison with LI plants. Probably, systemic signals triggered by a high PFD caused early senescence and diminished oxidative protection in primary leaves of sunflower plants as a result., L. De la Mata ... [et al.]., and Obsahuje bibliografii
The goldfish (Carassius auratus gibelio Bloch.) were exposed to cadmium in the concentration of 20 mg Cd/1 water under aquarium conditions for 1, 4, 7 and 15 days. After exposure to cadmium, the activities of superoxide dismutase (SOD) and catalase (CAT) were significantly decreased. At the same time, the liver ascorbic acid (AsA) content was increased.
L-arginine is a substrate for nitric oxide synthase (NOS) responsible for the production of NO. This investigation studied the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on L-arginine-induced oxidative stress and hypotension. Forty Wistar-Kyoto rats were treated for 14 days with vehicle, L-arginine (12.5 mg/ml p.o.), L-arginine + apocynin (2.5 mmol/l p.o.), L-arginine + catalase (10000 U/kg/day i.p.) and L-arginine plus apocynin + catalase respectively. Weekly renal functional and hemodynamic parameters were measured and kidneys harvested at the end of the study for histopathological and renal NADPH oxidase 4 (Nox4) assessments. L-arginine administration in normotensive rats decreased systolic blood pressure (120±2 vs. 91±2 mmHg) and heart rate (298±21 vs. 254±15 bpm), enhanced urinary output (21.5±4.2 vs. 32±1.9 ml/24 h, increased creatinine clearance (1.72±0.56 vs. 2.62±0.40 ml/min/kg), and fractional sodium excretion (0.88±0.16 vs. 1.18±0.16 %), caused proteinuria (28.10±1.93 vs. 35.26±1.69 mg/kg/day) and a significant decrease in renal cortical blood perfusion (292±3 vs. 258±5 bpu) and pulse wave velocity (3.72±0.20 vs 2.84±0.13 m/s) (all P<0.05). L-arginine increased plasma malondialdehyde (by ~206 % P<0.05) and NO (by ~51 %, P<0.05) but decreased superoxide dismutase (by ~31 %, P<0.05) and total antioxidant capacity (by ~35 %, P<0.05) compared to control. Renal Nox4 mRNA activity was approximately 2.1 fold higher (P<0.05) in the L-arginine-treated rats but was normalized by apocynin and apocynin plus catalase treatment. Administration of apocynin and catalase, but not catalase alone to rats fed L-arginine, restored the deranged renal function and structure, prevented hypotension and enhanced the antioxidant capacity and suppressed Nox4 expression. These findings suggest that apocynin and catalase might be used prophylactically in the states of oxidative stress.
Twelve-day-old barley seedlings were supplied with 23 μM methyl jasmonate (MeJA) or 10 μM paraquat (Pq) via the transpiration stream and kept in the dark for 24 h. Then they were exposed to 100 μmol m-2 s-1 PAR and samples were taken 1, 2, 3, and 6 h after irradiation. Treatment of seedlings with MeJA alone resulted in decreased content of chlorophyll (Chl), and net photosynthetic (PN) and transpiration rates. Pq treatment led to a decrease in Chl content and to a very strong inhibition of PN, the effects were manifested by 1 h of irradiation. Pq treatment did not affect the activity of ribulose-1,5 bisphosphate carboxylase (RuBPC, EC 4.1.1.39) but increased the activity of the photorespiratory enzymes phosphoglycolate phosphatase (PGP, EC 3.1.3.18), glycolate oxidase (GO, EC 1.1.3.1), and catalase (EC 1.11.1.6). Pre-treatment of seedlings with MeJA before exposure to Pq fully blocked the inhibitory effect of Pq on photosynthesis and protected against subsequent Pq-induced oxidative damage. and V. A. Hristova, L. P. Popova.
A crop legume Vigna unguiculata L. (Walp.) and a wild legume Crotalaria juncea L. were evaluated for their relative responses to the oxidative stress injury induced by various doses of UV-B radiation (UV-B, 280-315 nm; 0, 1.0, 1.4, 4.7, and 6.0 kJ m-2 d-1). A dose-dependent damage in lipid peroxidation was determined as an index of membrane injury caused by UV-B. The impact was significantly higher in V. unguiculata than in C. juncea. The specific activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase increased directly proportional to UV-B doses. However, the activities of these enzymes were significantly higher in V. unguiculata than in C. juncea indicating that V. unguiculata was inflicted with more severe oxidative stress injury under UV-B. In C. juncea the glutathione reductase and ascorbate oxidase activities were 35 and 40 % greater than in V. unguiculata, respectively. Further, the non-enzymatic antioxidants ascorbate and glutathione, and their reduced/oxidizes ratios in C. juncea were much greater than V. unguiculata indicating C. juncea has an inherently greater antioxidative potential than V. unguiculata. Thus C. juncea is better adapted to oxidative stress than V. unguiculata by means of efficient cellular antioxidant mechanisms helping to combat the photooxidative stress injury elicited by UV-B.