Abstract
In a study of the plant communities of two Australian rainforests, it was found that pioner species had high levels of nitrate reductase (EC 1.6.6.1) and were predominantly leaf nitrate assimilators. Under‐ and over‐storey species had low levels of shoot and root nitrate reductase activity, and many of them showed little capacity for nitrate reduction even when nitrate ions were freely available. Although closed‐forest species have lower levels of nitrate reductase than those of gaps and forest margins, their total nitrogen contents were similar, suggesting the former utilize nitrogen sources other than nitrate ions. Glutamine synthetase (EC 6.3.1.2) was present in the leaves of all species examined. In the leaves of pioneer species the chloroplastic isoform of glutamine synthetase predominted, while in most of the species typical of closed‐forest the cytosolic isoform accounted for at least 40% of total leaf activity. Low levels of chloroplastic glutamine synthetase were correlated with a low capacity for leaf nitrate reduction, and both are characteristic of many species that regenerate and grow for some time in shade. Low levels of chloroplastic glutamine synthetase imply that, in some of these woody plants, photorespiratory ammonia is re‐assimilated via cytosolic glutamine synthetase.
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Claims 12
Claim · model-written summary
Pioneer species had high nitrate reductase levels and chiefly assimilated nitrate in leaves.
Verbatim
e0“pioner species had high levels of nitrate reductase (EC 1.6.6.1) and were predominantly leaf nitrate assimilators”
Claim · model-written summary
Understorey and overstorey species had low shoot and root nitrate reductase activity.
Verbatim
e0“Under‐ and over‐storey species had low levels of shoot and root nitrate reductase activity”
Claim · model-written summary
Many understorey and overstorey species had little nitrate reduction capacity even with nitrate freely available.
Verbatim
e0“many of them showed little capacity for nitrate reduction even when nitrate ions were freely available”
t0“plants of Austrlian rainforest communities”
Claim · model-written summary
Closed forest species had lower nitrate reductase levels than gap and forest margin species.
Verbatim
e0“closed‐forest species have lower levels of nitrate reductase than those of gaps and forest margins”
Claim · model-written summary
Closed forest species had similar total nitrogen content to gap and forest margin species.
Verbatim
e0“their total nitrogen contents were similar”
t0“plants of Austrlian rainforest communities”
Claim · model-written summary
The authors suggest closed forest species use nitrogen sources other than nitrate ions.
Verbatim
e0“suggesting the former utilize nitrogen sources other than nitrate ions”
t0“plants of Austrlian rainforest communities”
Claim · model-written summary
Glutamine synthetase was present in leaves of every examined species.
- Taxon
- plants of Austrlian rainforest communitiest0
- Organ / stage
- leavese0
- Gene
- Glutamine synthetasee0
- Outcome
- present in the leaves of all species examinede0
Not reportedDirection
Verbatim
e0“Glutamine synthetase (EC 6.3.1.2) was present in the leaves of all species examined”
t0“plants of Austrlian rainforest communities”
Claim · model-written summary
The chloroplastic glutamine synthetase isoform predominated in pioneer leaves.
Verbatim
e0“In the leaves of pioneer species the chloroplastic isoform of glutamine synthetase predominted”
Claim · model-written summary
The cytosolic isoform represented at least 40% of total leaf activity in most closed forest species.
Verbatim
e0“in most of the species typical of closed‐forest the cytosolic isoform accounted for at least 40% of total leaf activity”
Claim · model-written summary
Low chloroplastic glutamine synthetase levels correlated with low leaf nitrate reduction capacity.
Verbatim
e0“Low levels of chloroplastic glutamine synthetase were correlated with a low capacity for leaf nitrate reduction”
t0“plants of Austrlian rainforest communities”
Claim · model-written summary
Low chloroplastic glutamine synthetase and nitrate reduction capacity characterized species regenerating in shade.
- Taxon
- plants of Austrlian rainforest communitiest0
- Outcome
- regenerate and grow for some time in shadee0
- Setting
- shadee0
Not reportedDirection
Verbatim
e0“both are characteristic of many species that regenerate and grow for some time in shade”
t0“plants of Austrlian rainforest communities”
Claim · model-written summary
The authors infer cytosolic glutamine synthetase reassimilates photorespiratory ammonia in some woody plants.
Verbatim
e0“in some of these woody plants, photorespiratory ammonia is re‐assimilated via cytosolic glutamine synthetase”