IN VIVO GIBBERELLIN A9 METABOLISM BY AZOSPIRILLUM SP. IN dy DWARF RICE MUTANT SEEDLINGS

CASSÁN FD; BOTTINI R; PICCOLI P

HORTSCIENCE

AMER SOC HORTICULTURAL SCIENCE

Año: 2001 vol. 28 p. 124 - 129

0018-5345

Azospirillum sp. are bacteria beneficial to inoculated plants, and the effect is partially attributed to gibberellin production. Deutero-labelled GA9 was fed to dy mutant rice-dwarf seedlings inoculated with A. lipoferum or A. brasilense and/or treated with Prohexadione-Ca, an inhibitor of late steps in gibberellin biosynthesis. According to the shoot growth response, the mutant showed the ability to perform 3?-hydroxylation of the d2GA9 fed. This ability was partially blocked by Prohexadione-Ca, suggesting that GA9 may have some activity per se. After the feeding was done along with Azospirillum sp. inoculation, the bacteria performed 3?-hydroxylation as shown by shoot growth promotion and corroborated by GC-MS detection of d2GA3. The growth promotion was blocked by Prohexadione-Ca but in a lower extent as compared with non-inoculated controls, suggesting that the inhibitor worked on the 3?- hydroxylation performed on the substrate fed but on the microorganism capacity to produce “active” gibberellins