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Glass, A.D.M., Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Erner, Y., Department of Citriculture, ARO, Volcani Centre, Bet-Dagan 50250, Israel
Kronzucker, H.J., Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada, Soil and Water Sciences Division, International Rice Research Institute, P.O.Box 933, Manila, Philippines
Schjoerring, J.K., Plant Nutrition Laboratory, Royal Veterinary and Agriculture University, DK-1871 Frederiksberg, Denmark
Siddiqi, M.Y., Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Wang, M.-Y., AgBiotech Centre, Cook College, Rutgers University, New Brunswick, NJ 08903-0231, United States
Ammonium uptake across the plasma membranes of seedling roots of intact rice plants is thermodynamically active at low external concentrations, and consequently, electrogenic uniport is an unlikely mechanism for influx. At higher NH4 + concentrations uptake is passive and electrogenic uniport is a possibility. While passive permeation of NH3 is also possible at high external [NH4 +], influx measurements at 10 mM NH4 + demonstrated a pH dependence which was inconsistent with significant NH3 permeation. Kinetic studies using 13NH4 + established that influx at low external [H4 +] occurred via high affinity transport systems (HATS) in rice and spruce, while at higher [NH4 +], influx was mediated by low affinity transport systems (LATS), that showed linear concentration dependence. Ammonium influx via the HATS was shown to be up-regulated or down-regulated in response to changes of N status, whereas influx in the LATS was insensitive to N status. The identity or identities of the regulatory signals responsible for controlling influx are discussed. © VCH Verlagsgesellschaft mbH, 1997.
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Ammonium fluxes into plant roots: Energetics, kinetics and regulation
160
Glass, A.D.M., Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Erner, Y., Department of Citriculture, ARO, Volcani Centre, Bet-Dagan 50250, Israel
Kronzucker, H.J., Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada, Soil and Water Sciences Division, International Rice Research Institute, P.O.Box 933, Manila, Philippines
Schjoerring, J.K., Plant Nutrition Laboratory, Royal Veterinary and Agriculture University, DK-1871 Frederiksberg, Denmark
Siddiqi, M.Y., Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Wang, M.-Y., AgBiotech Centre, Cook College, Rutgers University, New Brunswick, NJ 08903-0231, United States
Ammonium fluxes into plant roots: Energetics, kinetics and regulation
Ammonium uptake across the plasma membranes of seedling roots of intact rice plants is thermodynamically active at low external concentrations, and consequently, electrogenic uniport is an unlikely mechanism for influx. At higher NH4 + concentrations uptake is passive and electrogenic uniport is a possibility. While passive permeation of NH3 is also possible at high external [NH4 +], influx measurements at 10 mM NH4 + demonstrated a pH dependence which was inconsistent with significant NH3 permeation. Kinetic studies using 13NH4 + established that influx at low external [H4 +] occurred via high affinity transport systems (HATS) in rice and spruce, while at higher [NH4 +], influx was mediated by low affinity transport systems (LATS), that showed linear concentration dependence. Ammonium influx via the HATS was shown to be up-regulated or down-regulated in response to changes of N status, whereas influx in the LATS was insensitive to N status. The identity or identities of the regulatory signals responsible for controlling influx are discussed. © VCH Verlagsgesellschaft mbH, 1997.
Scientific Publication
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