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Cyclic variations in nitrogen uptake rate of soybean plants: effects of pH and mixed nitrogen sourcesTo determine if the daily pattern of NO3- and NH4+ uptake is affected by acidity or NO3- : NH4+ ratio of the nutrient solution, non-nodulated soybean plants (Glycine max) were exposed for 21 days to replenished, complete nutrient solutions at pH 6.0, 5.5, 5.0, and 4.5 which contained either 1.0 mM NH4+, 1.0 mM NO3- [correction of NO3+], 0.67 mM NH4+ plus 0.33 mM NO3- (2:1 NH4+ : NO3-) [correction of (2:1 NH3+ : NO4-)], or 0.33 mM NH4+ plus 0.67 mM NO3- (1:2 NH4+ : NO3-). Net uptake rates of NH4+ and NO3- were measured daily by ion chromatography as depletion from the replenished solutions. When NH4+ and NO3- were supplied together, cumulative uptake of total nitrogen was not affected by pH or solution NH4+ : NO3- ratio. The cumulative proportion of nitrogen absorbed as NH4+ decreased with increasing acidity; however, the proportional uptake of NH4+ and NO3- was not constant, but varied day-to-day. This day-to-day variation in relative proportions of NH4+ and NO3- absorbed when NH4+ : NO3- ratio and pH of solution were constant indicates that the regulatory mechanism is not directly competitive. Regardless of the effect of pH on cumulative uptake of NH4+, the specific nitrogen uptake rates from mixed and from individual NH4+ and NO3- sources oscillated between maxima and minima at each pH with average periodicities similar to the expected interval of leaf emergence.
Document ID
20040090209
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Raper, C. D. Jr
(North Carolina State University Raleigh)
Vessey, J. K.
Henry, L. T.
Chaillou, S.
Date Acquired
August 21, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Plant physiology and biochemistry : PPB / Societe francaise de physiologie vegetale
Volume: 29
Issue: 3
ISSN: 0981-9428
Subject Category
Man/System Technology And Life Support
Funding Number(s)
CONTRACT_GRANT: NCC2-101
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Number 61-10
NASA Program CELSS
NASA Discipline Life Support Systems

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