Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: UNIPROT:P39060 (
endostatin
)
2,284
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
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
