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Diurnal nitrate uptake in young tomato (Lycopersicon esculentum Mill.) plants: test of a feedback-based model 总被引:3,自引:0,他引:3
A simple model is proposed to describe diurnal net nitrate uptake rate
patterns observed experimentally on young plants grown under constant
non-limiting nutrition. It rests on two hypotheses: net uptake rate is
under negative feedback control by internal plant nitrate content, and
nitrogen metabolism occurs only during the light period. The model
parameters were determined from the results of three independent
experiments performed under non-disturbing conditions in a growth room at
constant air and solution temperatures. Net hourly nitrate uptake rate was
measured through a diurnal cycle and after an extended 28 h period of
darkness. It increased continuously during the light period and decreased
during the dark period. Under prolonged darkness, net uptake declined to an
asymptotic positive uptake rate of about 10-5 mol
h-1 g-1 total plant dry
weight. The measured hourly nitrate uptake rate values were consistent with
independent determinations of long-term nitrate and total N accumulations
in the plant. Realistic simulations of experimental data are achieved with
the proposed model. Furthermore, the maintenance of a positive net uptake
rate, measured in non-growing plants subjected to prolonged darkness, is
explained in the model by the continuous increase of plant water content.
The importance of the diurnal variations of plant water content for nitrate
uptake rate is emphasized and gives consistency to the homeostasis
hypothesis of the model. The diurnal changes in nitrate uptake predicted by
the model are strongly dependent on the assumption made for diurnal changes
in nitrate assimilation. While the purely photosynthetic assumption is
convenient, a more realistic metabolism sub-model is
needed. 相似文献
2.
Cardenas-Navarro R; Adamowicz S; Gojon A; Robin P 《Journal of experimental botany》1999,50(334):625-635
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. 相似文献
3.
Nitrate accumulation in plants: a role for water 总被引:10,自引:0,他引:10
Plant nitrate and water contents (g-1 dry weight)
were monitored (1) in tomato plants in a growth room, during the day/night
cycle with varied light intensities; (2) in two lettuce cultivars during
the day/night cycle in a growth room and during growth in a glasshouse.
Large, concurrent, and linearly correlated changes in nitrate and water
contents were observed in both species and time-scales. Although these
changes were dependent on light intensity and other environmental
conditions, the slope of their relationship was not affected. Furthermore,
when a limiting nitrate nutrition regime was applied to tomato, a
significant and concurrent reduction of both plant nitrate and water
contents was observed. Thus, when compared on the same water content basis,
their nitrate content was only slightly reduced. These nitrate and water
content changes were also observed in plant parts, and confirmed, through
data extracted from the literature, in a large number of species (annuals
and perennials) and other environments (open-field, soil culture). They are
interpreted as an effect of homoeostasis for endogenous nitrate
concentration (mol m-3), and it is suggested that
nitrate content changes (mol g-1 dry wt.) result
from the varying size of a water reservoir (m3
g-1 dry wt.) whose nitrate concentration is
regulated. From this viewpoint, the concept of critical nitrate
concentration is discussed, and it is proposed to introduce explicitly
water content in plant nitrogen models.Keywords:
Nitrate content, water content, homoeostasis.
相似文献
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