ALTERED ROOT HAIR MORPHOGENESIS IN PHASEOLUS-VULGARIS IN RESPONSE TO BACTERIAL COINOCULATION AND THE PRESENCE OF AMINOETHOXY VINYL GLYCINE (AVG)

Treatment of Phaseolus vulgaris seedlings with the biosynthesis inhibi tor, aminoethoxy vinyl glycine (AVG), resulted in a loss of root hair formation. Addition of the ethylene precursor 1-aminocyclopropane-1-ca rboxylic acid (ACC) to the growth medium enhanced root hair formation in P. vulgaris, in the absence of AVG. The inhibitory effect of AVG on root hair formation was reversed by the combined presence of Rhizobiu m etli TAL 182 and Bacillus megaterium S49 on P. vulgaris roots. Plant s that received single inoculation of either Rhizobium TAL 182 or Baci llus S49 did not show enhancement of root hair formation when AVG was present in the growing medium. These results are consistent with the a ction of ACC as a positive regulator of root hair morphogenesis. The d ata suggest that the bacterial interaction may act through the ethylen e biosyntheses pathway to enhance root hair morphogenesis, and to disr upt the normal pattern of root epidermal cell development.