Abstract
Biogenic amines occupy an important position among the many nitrogenous plant compounds. Polyamines are part of the overall metabolism of nitrogenous compounds, yet they do not seem to function in the ‘normal’ nitrogen nutrition. Rather, these widespread polycations (e. g. putrescine, spermidine and spermine) are involved in the regulation of growth and stress, probably by binding to negatively charged macromolecules. In addition, some diamines and polyamines are metabolized to yield 'secondary ’metabolites such as nicotine and other alkaloids. Previous studies have indicated that the ratio of nitrate to ammonium nutrition affects polyamine biosynthesis and content in intact plants. Thus, an increase in putrescine accumulation was found under conditions of excess ammonium ions, relative to nitrate. Modifications of nitrogen sources in the culture medium of tobacco cell suspensions (depletion of ammonium nitrate, or potassium nitrate, or both) resulted in marked changes in the content of cellular free polyamines. Considerable changes in the content of specific polyamines were also found with exposure to specific inhibitors of polyamine biosynthesis (difluoromethyl ornithine, difluoromethyl arginine, cyclohexylamine, methylglyoxal‐bis‐guanylhydrazone). However, a combination of nitrogen depletion of the medium and some inhibitors resulted in a very marked over‐production of spermidine and spermine. The significance of these findings is discussed in relation to the assumption that polyamines act as a metabolic buffer, and maintain cellular pH under conditions where ammonium assimilation produces an excess of protons.
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Claims 4
Claim · model-written summary
Excess ammonium increased putrescine accumulation relative to nitrate.
Verbatim
e0“an increase in putrescine accumulation was found under conditions of excess ammonium ions, relative to nitrate”
t0“plants”
Claim · model-written summary
Changing nitrogen sources in tobacco suspension medium markedly changed cellular free polyamine content.
- Taxon
- tobacco
Nicotiana tabacume0 - Treatment
- depletion of ammonium nitrate, or potassium nitrate, or bothe0
- Outcome
- content of cellular free polyaminese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Modifications of nitrogen sources in the culture medium of tobacco cell suspensions (depletion of ammonium nitrate, or potassium nitrate, or both) resulted in marked changes in the content of cellular free polyamines”
Claim · model-written summary
Exposure to polyamine-biosynthesis inhibitors markedly changed specific polyamine content.
- Taxon
- plantsViridiplantaet0
- Treatment
- specific inhibitors of polyamine biosynthesise0
- Outcome
- content of specific polyaminese0
Not reportedComparatorDirection
Verbatim
e0“Considerable changes in the content of specific polyamines were also found with exposure to specific inhibitors of polyamine biosynthesis (difluoromethyl ornithine, difluoromethyl arginine, cyclohexylamine, methylglyoxal‐bis‐guanylhydrazone)”
t0“plants”
Claim · model-written summary
Combined nitrogen depletion and some inhibitors strongly increased spermidine and spermine production.
- Taxon
- plantsViridiplantaet0
- Treatment
- a combination of nitrogen depletion of the medium and some inhibitorse0
- Outcome
- production of spermidine and sperminee0
- Direction
- over‐productione0
Not reportedComparator
Verbatim
e0“a combination of nitrogen depletion of the medium and some inhibitors resulted in a very marked over‐production of spermidine and spermine”
t0“plants”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.