Categories
Orlando+FL+Florida hookup sites

Effects of exogenous source of GABA, Gln, Glu and Asn on nitrate consumption

Effects of exogenous source of GABA, Gln, Glu and Asn on nitrate consumption

In order to test the hypothesis that GABA could up-regulate nitrate uptake, the effect of exogenous supply of different amino acids was compared with control plants. Gln, Glu and Asn are known to act as inhibitors of nitrate uptake at the millimolar range in many species when supplied to the root nutrient solution ( Muller & Touraine 1992 ; Vid ). Therefore, roots were supplied with either 1 m m Gln, 1 m m Glu or 1 m m Asn, whereas two concentrations were tested for the GABA treatment, 100 µ m and 1 m m (Fig. 5). A positive and significant effect on 15 NOstep three – influx was observed for 100 µ m (P < 0.05) and no significant effect for 1 m m GABA (P > 0.05)-treated plants compared with the control plants, whereas 15 NO3 – influx was significantly reduced by the Gln, Glu and Asn root treatments (Fig. 5a). The strongest negative effect on nitrate uptake was due to Glu (38% inhibition) followed by Asn (37% inhibition) and Gln (33% inhibition). In parallel, Northern blot analyses performed with mRNA extracted from the same amino acid treated plants confirmed previous results for all of the amino acids tested. Thus, BnNrt2 mRNA abundance was enhanced by 1.6- and 1.3-fold in response to 100 µ m and 1 m m GABA treatments, respectively.