Modelling nitrate influx in young tomato (Lycopersicon esculentum Mill.) plants |
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Authors: | Cardenas-Navarro R; Adamowicz S; Gojon A; Robin P |
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Institution: | Ecophysiologie et Horticulture, INRA, domaine St Paul, site AGROPARC, F-84914 Avignon Cedex 9, France; Biochemie et Physiologie Moléculaire des Plantes, ENSA-M/INRA/CNRS URA 2133 Place Viala, F-34060 Montpellier Cedex 1, France; Corresponding author; Fax: +33 4 90 31 60 28; E-mail: adamow@avignon.inra.fr |
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Abstract: | The effects of light and NO3- nutrition on
15NO3- influx in roots were
investigated in young, 19-d-old, induced tomato plants grown at a constant
air and solution temperature of 20C. Nitrate
influx was measured by 15N accumulation for 5 min,
on plants exposed to a wide range of exogenous concentrations, from 10 x
10-3 to 30 mol m-3. Influx
kinetics, fitted to the data following a non-linear procedure, showed
multiphasic patterns. The best fits were obtained when three pure and
non-additive Michaelis-Menten kinetics were applied, with phase transitions
at approximately 0.8 and 4 mol m-3. In plants grown
at 3.0 mol m-3 NO3-, the
asymptotic maximum influx rate (Imax) of each phase
declined during the night until 24 h darkness. At the end of the day
period, about a 2-fold enhancement of Imax was
observed when plants were pretreated for 3 d with 0.2 instead of 3.0 mol
m-3 NO3-. The influx rates
measured at any given NO3- concentration and the
Imax for any phase showed a negative non-linear
correlation with plant nitrate concentration. Furthermore, the results
suggest the existence of a set point, approximately 66 mol
m-3 plant nitrate, for which influx is null at any
given solution nitrate concentration. A model using modified
Michaelis-Menten kinetics is proposed to predict the influx rate as a
function of both solution and plant NO3-
concentrations. |
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