Abstract
AIMS: The capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role? METHODS: Growing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases. RESULTS: We found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity. CONCLUSIONS: Our results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture.
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Claims 5
Claim · model-written summary
Maize and wheat roots showed little free protease secretion, with activity mostly root-bound.
- Taxon
- maize and wheat
Triticum aestivum
Zea mayse0 - Organ / stage
- root surfacee0
- Outcome
- secretion of free proteasese0
- Direction
- little evidencee0
- Setting
- sterile hydroponic conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases. RESULTS: We found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface.”
Claim · model-written summary
Nitrogen deficiency did not stimulate root protease activity.
- Taxon
- maize and wheatTriticum aestivumZea mayse1
- Treatment
- N deficiencye0
- Outcome
- Root protease activitye0
- Direction
- not stimulatede0
- Comparator
- with and without inorganic Ne1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root protease activity was not stimulated under N deficiency.”
e1“Growing maize and wheat under sterile hydroponic conditions with and without inorganic N”
Claim · model-written summary
Cereal roots were estimated to contribute one-fifth of rhizosphere protease activity.
Verbatim
e0“Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity.”
Claim · model-written summary
Plant nitrogen uptake from soil protein was inferred to matter only when protein directly contacts root surfaces.
Verbatim
e0“Our results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces.”
Claim · model-written summary
The lack of protease upregulation under N deficiency suggests root protease activity is unrelated to enhanced soil nitrogen capture.
- Taxon
- maize and wheatTriticum aestivumZea mayse1
- Outcome
- enhanced soil N capturee0
- Qualifier
- lack of protease upregulation under N deficiencye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture.”
e1“Growing maize and wheat under sterile hydroponic conditions”
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