RESPONSES OF SOYBEAN AND COWPEA ROOT MEMBRANES TO INOCULATION WITH AZOSPIRILLUM-BRASILENSE

Inoculation with Azospirillum brasilense Cd of two leguminous species, soybean (Glycine max) and cowpea (Vigna unguiculata), demonstrated that: (1) A. brasilense significantly increased proton efflux from their roots; (2) inoculation reduced plant membrane potential (in soybean), (3) inoculation changed the phospholipid quantity in plant membranes of calli (in cowpea), and (4) a low molecular weight "bacterial signal" may be responsible for these effects. We suggest that plant membranes can serve as a reliable sensor for the effect of Azospirillum on plants and are probably a primary target for Azospirillum on plant roots.