Effects of hypoxia on 13NH4+ fluxes in rice roots: kinetics and compartmental analysis

Techniques of compartmental (efflux) and kinetic influx analyses with the radiotracer 13NH4+ were used to examine the adaptation to hypoxia (15, 35, and 50% O2 saturation) of root N uptake and metabolism in 3-week-old hydroponically grown rice (Oryza sativa L., cv IR72) seedlings. A time-dependence...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1998-02, Vol.116 (2), p.581-587
Main Authors: Kronzucker, H.J. (International Rice Research Institute, Manila, Philippines.), Kirk, G.J.D, Siddiqi, M.Y, Glass, A.D.M
Format: Article
Language:English
Subjects:
ABONOS NITROGENADOS
ABSORCION DE SUSTANCIAS NUTRITIVAS
ABSORPTION DE SUBSTANCES NUTRITIVES
ADAPTACION
ADAPTATION
Agronomy. Soil science and plant productions
AMMONIA
AMMONIAC
AMONIACO
ANAEROBIC CONDITIONS
ANAEROBIOSE
ANAEROBIOSIS
Biological and medical sciences
ECHANGE D'ION
Economic plant physiology
ENGRAIS AZOTE
Fundamental and applied biological sciences. Psychology
INTERCAMBIO IONICO
ION EXCHANGE
ISOTOPE RADIOACTIF
MEASUREMENT
MEDICION
MESURE
Metabolism
NITROGEN FERTILIZERS
Nitrogen metabolism
Nitrogen metabolism and other ones (excepting carbon metabolism)
NUTRIENT UPTAKE
Nutrition. Photosynthesis. Respiration. Metabolism
ORYZA SATIVA
Plant physiology and development
RACINE
RADIOACTIVE TRACERS
RADIOISOTOPES
RADIOISOTOPOS
RAICES
ROOTS
STRESS RESPONSE
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Summary:Techniques of compartmental (efflux) and kinetic influx analyses with the radiotracer 13NH4+ were used to examine the adaptation to hypoxia (15, 35, and 50% O2 saturation) of root N uptake and metabolism in 3-week-old hydroponically grown rice (Oryza sativa L., cv IR72) seedlings. A time-dependence study of NH4+ influx into rice roots after onset of hypoxia (15% O2) revealed an initial increase in the first 1 to 2.5 h after treatment imposition, followed by a decline to less than 50% of influx in control plants by 4 d. Efflux analyses conducted 0, 1, 3, and 5 d after the treatment confirmed this adaptation pattern of NH4+ uptake. Half-lives for NH4+ exchange with subcellular compartments, cytoplasmic NH4+ concentrations, and efflux (as percentage of influx) were unaffected by hypoxia. However, significant differences were observed in the relative amounts of N allocated to NH4+ assimilation and the vacuole versus translocation to the shoot. Kinetic experiments conducted at 100, 50, 35, and 15% O2 saturation showed no significant change in the K(m) value for NH4+ uptake with varying O2 supply. However, V(max) was 42% higher than controls at 50% O2 saturation, unchanged at 35%, and 10% lower than controls at 15% O2. The significance of these flux adaptations is discussed
ISSN:0032-0889
1532-2548