Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A pH dependent reduction in growth, pigment, ATP content, O2- evolution, carbon fixation, photosynthetic electron transport system, nutrient uptake (NO3- and NH4+), nitrate reductase, and ATPase activities and increase in K+ efflux of Chlorella vulgaris was noticed following supplementation of Cu and Ni to the culture medium. PS II was found to be more sensitive to both pH and metals than PS I. Though, nitrate reductase (NR) was more sensitive to both pH and metals, the ATPase was however, more sensitive to metals but less sensitive to acidic pH. Acid pH was found to inhibit the nutrient (NO3- and NH4+) uptake and nitrate reductase in a non-competitive manner. The inhibition produced by the test metals alone was of non-competitive type for NO3- uptake, nitrate reductase and ATPase and competitive for NH4+ uptake. Acidity not only inhibited the metabolic variables directly but also through facilitated uptake of metals and increased membrane permeability. A very low sensitivity of ATPase to acidic pH seems to be responsible for the survival of algae in acid environment.
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PMID:Effect of Cu and Ni on growth, mineral uptake, photosynthesis and enzyme activities of Chlorella vulgaris at different pH values. 802 20

This study concerns the inhibitory effects of acid pH and nickel on growth, nutrient (NO3- and NH4+) uptake, carbon fixation, O2 evolution, electron transport chain and enzyme (nitrate reductase and ATPase) activities of acid tolerant and wild-type strains of Chlorella vulgaris. Though a general reduction in all these variables was noticed with decreasing pH, the tolerant strain was found to be metabolically more active than the wild-type. A reduced cation (NH4+, Na+, K+ and Ca2+) uptake, coupled with a facilitated influx of anions (NH4+, PO4(3-) and HCO3-), suggested the development of a positive membrane potential in acid tolerant Chlorella. Nevertheless, a tremendous increase in ATPase activity at decreasing pH revealed the involvement of superactive ATPase in exporting H+ ions and keeping the internal pH neutral. A difference in Na+ and K+ efflux of the two strains at decreasing pH suggests there is a difference in membrane permeability. The low toxicity of Ni in the acid tolerant strain may be due to the low Ni uptake brought about by a change in membrane potential as well as in permeability. Hence, the development of superactive ATPase and a change in both membrane potential and permeability not only offers protection against acidity, but also co-tolerance to metals.
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PMID:Effect of nickel on certain physiological and biochemical behaviors of an acid tolerant Chlorella vulgaris. 814 21

Acidic deposition in high-elevation forests in the Appalachian Mountains of the eastern United States has been implicated in the decline of red spruce (Picea rubens Sarg.). Elevated soil acidity may increase soil Al availability and toxicity to roots. Enhanced soil solution NO(3) (-) concentrations, resulting from precipitation inputs and enhanced soil organic matter mineralization, may exacerbate Al toxicity by increasing root Al uptake. We exposed red spruce seedlings to 350, 500, 800 or 1400 micro M NO(3) (-) and 0 or 200 micro M Al in a factorial design in sand-nutrient solution culture to test if increased NO(3) (-) concentrations enhance Al uptake and toxicity. In addition to significant reductions in seedling growth parameters resulting from Al exposure, we found significant interactions between NO(3) (-) and Al for seedling height growth rate, needle weight, shoot weight and root weight. Differences in these parameters between Al treatments became more pronounced as solution NO(3) (-) concentration increased and reflected an Al-mediated inhibition of seedling response to increasing NO(3) (-) concentration. Solution NO(3) (-) concentrations above 500 micro M induced root nitrate reductase (NR) activity, whereas shoot NR activity increased in response to NO(3) (-) up to 500 micro M and declined above that concentration. In contrast, exposure to Al depressed NR activity of roots but tended to stimulate needle NR activity. Foliar N concentrations increased in seedlings grown in cultures containing between 350 and 500 micro M NO(3) (-), with no change above 500 micro M. Increasing concentrations of NO(3) (-) depressed foliar P concentrations, with reductions being greatest in seedlings exposed to 1400 micro M NO(3) (-). Exposure to Al increased foliar Ca, K and Al concentrations, decreased foliar P concentrations, and inhibited increases in foliar Mg concentration in response to increasing NO(3) (-). The consistent interactions between NO(3) (-) and Al for growth, root NR activity and foliar Mg concentration were the result of an inhibition of seedling response to NO(3) (-) mediated by Al in solution, rather than enhanced Al toxicity resulting from growth in the presence of elevated NO(3) (-) concentrations.
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PMID:Effects of elevated nitrate and aluminum on the growth and nutrition of red spruce (Picea rubens) seedlings. 1496 76

The leaf anatomy and certain photosynthetic properties of nitrate- and ammonia-grown plants of Moricandia arvensis (L.) DC., a species previously reported to be a C(3)-C(4) intermediate, were investigated. Nitrate-grown plants had a high level of malate in the leaves while ammonia-grown plants had low levels of malate. In young leaves of nitrate-grown plants, there was a diurnal fluctuation of malate content, increasing during the day and decreasing during the night. Titratable acidity remained low in leaves of both nitrate- and ammonia-grown plants.In nitrate-grown plants, the activity of phosphoenolpyruvate (PEP) carboxylase was about 2-fold higher than in ammonia-grown plants, the latter having activity typical of C(3) species. Also, in nitrate-grown plants, the ratio of activities of ribulose 1,5-bisphosphate (RuBP) carboxylase/PEP carboxylase was lower than in ammonia-grown plants. Nitrate reductase activities were higher in nitrate- than in ammonia-grown plants and the greatest activity was found in younger leaves.With nitrate-grown plants, during a pulse-chase experiment the label in malate, as a percentage of the total labeled products, increased from about 7% after a 10-second pulse with (14)CO(2) up to 17% during a 5-minute chase with (12)CO(2). The pattern of (14)C labeling in various metabolites suggests the primary carboxylation is through RuBP carboxylase with a secondary carboxylation through PEP carboxylase. In similar experiments, with ammonia-grown plants, the percentage label in malate was only 0% to 4% with no increase in malate labeling during the chase period. The CO(2) compensation point was lower in nitrate-grown than ammonia-grown plants.There was no evidence of Kranz-like anatomy in either the nitrate or ammonia-grown plants. Mitochondria of bundle-sheath cells were strikingly positioned along the inner tangential wall. This might allow the chloroplasts of these cells to fix the mitochondrial photorespired CO(2) more effectively and contribute to the low CO(2) compensation point in the species. Chloroplasts of bundle-sheath cells and contiguous mesophyll cells were similar in size and structure in plants grown on different media, although chloroplast thylakoids and stromata of the ammonia-grown plants stained more intensely than those of nitrate-grown plants. In addition, irregular clusters of phytoferritin particles occurred in the chloroplasts of the ammonia-grown plants.The results indicate that the substantial activity of PEP carboxylase, incorporation of CO(2) into malate, the high malate content, and in part the relatively low CO(2) compensation point in Moricandia arvensis may be accounted for by metabolism of nitrate rather than by a state of C(3)-C(4) intermediacy.
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PMID:Influence of Nitrate and Ammonia on Photosynthetic Characteristics and Leaf Anatomy of Moricandia arvensis. 1666 44

Nitrate reductase activity (NRA) was found in primary roots, but not in foliage of red spruce (Picea rubens Sarg.) seedlings. Nitrate induced NRA:NH(4) (+) did not induce and slightly depressed NRA in older seedlings. Induction required 8 hours and, once induced, NRA decreased slowly in the absence of exogenous NO(3) (-). Seedlings were grown in perlite with a complete nutrient solution containing NH(4) (+) to limit NR induction. Established seedlings were stressed with nutrient solutions at pH 3, 4, or 5 supplemented with Cl(-) salts of Al, Cd, Pb, or Zn each at two concentrations. NRA in primary root tips was measured at 2, 14, 28, and 42 days. NRA induction was greatest at pH 3, and remained high during the period of study. NRA induction at pH 4 was lower. Metal ions suppressed NRA at pH 3 and 5, but enhanced NRA at pH 4. It is concluded that acidity and soluble metals in the root environment of red spruce are unlikely to be important factors in nitrogen transformations in red spruce roots.
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PMID:Nitrate reductase of primary roots of red spruce seedlings : effects of acidity and metal ions. 1666 91

North East region of India suffers from high sulphur coal mine overburden (OB) and plants those survive under such condition have adopted to such harsh environment. Here, we have investigated the effect of coal mine OB substrate on biochemical, physiological and growth of two shrubs Cassia (Cassia sofera L.) and Dhaincha (Sesbania rostrata L.); two tree species Gomari (Gmelina arborea L.) and Sisso (Dalbergia sisso L.); and two monocots Citronella Grass (Cymbopogon winterianus Jowitt) and Lemon Grass (Cymbopogon citratus L). The mine OB was found to be acidic (pH 2.0) with no true soil behavior, 12.5% sulphur and more than double the trace and heavy metals compared to normal control soil. Overall, high lipid peroxidation, membrane damage, peroxidase, glutathione reductase, ascorbate peroxidase, superoxide dismutase enzymes activities along with osmolyte proline and total soluble sugar was found in mine OB plants compared to control plants. While antioxidant activities were higher, nitrate reductase activity was significantly low but reduced leaf area, total shoot and root biomass. However, the responses of antioxidant activities in mine OB plants and control plants did not follow a standard pattern of higher activities in roots followed by old>young leaves or vice versa. Further, in mine OB plants, lipid peroxidation was found significantly higher for young citronella leaves. The levels of higher glutathione reductase was found in roots than the leaves except for old leaves in Gomari while ascorbate peroxidase was found in the leaves than the roots. Overall, all the species showed higher antioxidant enzyme activities, osmolyte accumulation and membrane damage possibly due to acidity and significantly higher limit of trace and heavy metals in mine OB substrate.
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PMID:Antioxidant, photosynthesis and growth characteristics of plants grown in high sulphur coalmine overburden. 3018 16

Humic substances (HS) are powerful natural plant biostimulants. However, there is still a lack of knowledge about the relationship between their structure and bioactivity in plants. We extracted HS (THE1-2) from two forest soils covered with Pinus mugo (1) or Pinus sylvestris (2). The extracts were subjected to weak acid treatment to produce size-fractionated HS (high molecular size, HMS1-2; low molecular size, LMS1-2). HS were characterized for total acidity, functional groups, element and auxin (IAA) contents, and hormone-like activity. HS concentrations ranging from 0 to 5 mg C L-1 were applied to garlic (Allium sativum L.) plantlets in hydroponics to ascertain differences between unfractionated and size-fractionated HS in the capacity to promote mineral nutrition, root growth and cell differentiation, activity of enzymes related to plant development (invertase, peroxidase, and esterase), and N (nitrate reductase, glutamine synthetase) and S (O-acetylserine sulphydrylase) assimilation into amino acids. A positive linear dose-response relationship was determined for all HS in the range 0-1 mg C L-1, while higher HS doses were less effective or ineffective in promoting physiological-biochemical attributes of garlic. Bioactivity was higher for size-fractionated HS according to the trend LMS1-2>HMS1-2>THE1-2, with LMS2 and HMS2 being overall more bioactive than LMS1 and HMS1, respectively. LMS1-2 contained more N, oxygenated functional groups and IAA compared to THE1-2 and HMS1-2. Also, they exhibited higher hormone-like activities. Such chemical properties likely accounted for the greater biostimulant action of LMS1-2. Beside plant growth, nutrition and N metabolism, HS stimulated S assimilation by promoting the enrichment of garlic plantlets with the S amino acid alliin, which has recognized beneficial properties in human health. Concluding, this study endorses that i) treating THE with a weak acid produced sized-fractionated HS with higher bioactivity and differing in properties, perhaps because of novel molecular arrangements of HS components that better interacted with garlic roots; ii) LMS from forest soils covered with P. mugo or P. sylvestris were the most bioactive; iii) the cover vegetation affected HS bioactivity iv); HS stimulated N and S metabolism with relevant benefits to crop nutritional quality.
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PMID:Bioactivity of Size-Fractionated and Unfractionated Humic Substances From Two Forest Soils and Comparative Effects on N and S Metabolism, Nutrition, and Root Anatomy of Allium sativum L. 3292 15