Without rhizobacterial inoculation or zeatin treatment, the total
amino acids concentration in the soil solution was about 11 mM
(Fig. 4). Mean concentrations of isoleucine and lysine were statistically
higher than those of other amino acids. Total concentration
of amino acids was not high, due to the short time of root growth in
the prewashed sand. However concentration of exudates is known
to increase greatly closer to the root surface (Darrah, 1991) and
consequently amino acid concentration might have been much
higher in the root vicinity. Moreover, the values we obtained are
close to those previously reported for wheat (Fig. 1 of Phillips et al.,
2004).