References

186 A. Deubel and W. Merbach
Fig. 2. P release from Ca3(PO4)2 by different bacterial strains with glucose or ribose as
C source (standing liquid culture 7 days at 28 ◦ C,4mg Cml −1 as sugar, 200 µgPml −1 as
Ca3(PO4)2)
well-nourished plants, with ribose, which is present in increasing amounts
under P deficiency (Deubel et al. 2000).
Although all strains were able to grow with both sugars as the C source,
Pantoea and Azospirillum increased P mobilization with ribose, while other
strains released less or no phosphate with this sugar. These changes in Pmobilizing
ability were combined with changes in the pattern of produced
carboxylic acids. The same results were found in the response of different
bacteria on synthetically mixed root exudates of well-nourished and Pdeficient
plants (Fig. 3).
Fig. 3. Influence of synthetic sugar mixtures [in analogy to the saccharide portion of root
deposits of Pisum sativum plants with P (pea exudates+P) and without P supply (pea
exudates – P)] in comparison to standard medium (glucose) on the Ca3(PO4)2 solubilizing
ability of the bacterial strains D 5/23, PsIA12 and CC 322