Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
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Target Concepts:
Gene/Protein
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Enzyme
Compound
Query: EC:1.7.1.2 (
nitrate reductase
)
3,861
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The total photosynthetic electron flux through PSII [J(e) (PSII)], the electron flux used for carbon assimilation [J(e) (PCR)], the electron flux used for photorespiration [J(e) (PCO)], the electron flux used for Mehler reaction [J(a) (O(2)-depend)] and the electron flux used for nitrogen metabolism [J(a) (O(2)-independ)] in leaves of
Rumex
K-1, a fodder crop with high protein content, were measured under three levels of nitrogen application (Fig.2). The
nitrate reductase
(NR) activity, glutamine synthetase (GS) activity, the leaf protein content, the chlorophyll content, P(n) and Phi (PSII) and F(v)/F(m) (Table 1) were also measured. The results showed that with the increase of nitrogen application, the NR and GS activities increased remarkably (Fig.3) and more electron flux was allocated to nitrogen metabolism as well as photorespiration (Fig.2). Nitrogen metabolism and carbon metabolism competed for energy, and the proportion of energy used in nitrogen metabolism to that used in carbon metabolism changed with nitrogen application rate. The electron flux used for nitrogen metabolism is about 15%-21% of the total electron flux under the three levels of nitrogen application (NO(3)(-) 0-30 mmol/L). Under lower nitrogen application, though energy used for carbon and nitrogen assimilation remarkably decreased, no significant increase of electron flux allocated to Mehler reaction was observed. The excess excitation energy in the leaves under the lower nitrogen application was efficiently dissipated via other energy dissipation mechanisms to protect the leaves against photo-damage.
...
PMID:[Effects of different nitrogen application rate on allocation of photosynthetic electron flux in Rumex K-1 leaves]. 1796 45
With
Rumex
obtusifolius L., the influence of some environmental conditions on nitrate uptake and reduction were investigated. Nitrate concentrations of plant material were determined by HPLC, the activity of
nitrate reductase
by an "in vivo" test. As optimal incubation medium, a buffer containing 0.04 M KNO
3
; 0.25 M KH
2
PO
4
; 1.5% propanol (v/v); pH 8.0 was found. Vacuum infiltration caused an increase of enzyme activity of up to 40%.High nitrate concentrations were found in roots and leaf petioles.
Nitrate reductase
activity of these organs, however, was low. On the other hand, the highest
nitrate reductase
activity was observed in leaf laminae, which contained lowest nitrate concentrations.In leaves, nitrate content and
nitrate reductase
activity exhibited inverse diurnal fluctuations. During darkness, decreasing activities of the enzyme were followed by increasing nitrate concentrations, while during light the contrary was true. In petioles diurnal fluctuations in nitrate content were observed, too. No significant correlations with illumination, however, could be found.Our results prove that
Rumex
obtusifolius is characterized by an intensive nitrate turnover. Theoretically, internal nitrate content of the plant would be exhausted within a few hours, if a supply via the roots would be excluded.
...
PMID:Nitrate content and nitrate reductase activity in Rumex obtusifolius L. : I. Differences in organs and diurnal changes. 2831 Nov 76
The aim of this work was to investigate the effect of nitrogen starvation and subsequent fentilization with nitrate or ammonium on nitrate content and
nitrate reductase
activity of
Rumex
obtusifolius L. under natural conditions.When plants were transplanted to nitrate-poor media, endogenous nitrate was reduced within a few days. In parallel, nitrage reductase activities dropped to about 25% of the initial values. As a consequence of nitrate fertilization (1; 10 or 100 mmol KNO
3
/l substrate), endogenous nitrate content of the plant abruptly increased within one day. In extreme cases, nitrate concentrations of up to 10% of plant dry weight could be observed without being lethal. High external nitrate concentrations caused an inhibition of
nitrate reductase
within the leaves, while low external concentrations provoked an increase in the enzyme activity of about 450% within one day. Ammonium fertilization (5 mmol (NH
4
)
2
SO
4
/l substrate) also caused an increase in
nitrate reductase
activity and nitrate content within leaf blades. This observation indicates a rapid nitrification of ammonium in the substrate. When plants were fertilized with ammonium plus nitrate (2.5 mmol (NH
4
)
2
SO
4
+ 5 mmol KNO
3
/l substrate), an extremely high and long term increase in nitrate reduction could be observed. Due to an intensive enzymatic nitrate turnover, the nitrate content of leaf blades then remained relatively low. Our observations do not point to an inhibition of
nitrate reductase
activity in leaves of
Rumex
obtusifolius by ammonium. Despite temporarily high endogenous nitrate concentrations,
Rumex
obtusifolius may not be termed as a "nitrate storage" plant, since the accumulation of nitrate is a short term process only.
...
PMID:Nitrate content and nitrate reductase activity in Rumex obtusifolius L. : II. Responses to nitrate starvation and nitrogen fertilization. 2831 Dec 15
