treatment are shown in Figure 2. In aerated
conditions, nitrate concentration in the medium
did not vary significantly, which is consistent with
the determinate phenotype of the Micro-Tom
cultivar which stops growing at the fruiting stage
(Marti et al., 2006). In contrast, in the non-aerated
nutrient solution, nitrate concentration decreased
markedly to reach about 1.4mM at day 6. This is in
agreement with the increase of nitrate uptake by
anoxic tomato roots described previously (Allegre
et al., 2004; Morard et al., 2004). Strikingly, in our
conditions, high concentrations of ammonium
were produced, indicating that most of the nitrate
was reduced to ammonium. In the first week,
the ratio of ammonium released to nitrate taken up
was lower than 1, which may be explained by
the storage of part of the ammonium in the
plant tissues during the first week (see below).
During weeks 2 and 3, ammonium present in the
medium was close to equimolar with nitrate
consumed.
Nitrite appeared in the nutrient solution 2 days
after the beginning of the experiment (Figure 2)
and increased in the following days but remained
low, around 1/10th of the amounts of absorbed