A PLANT GROWTH-PROMOTING BACTERIUM THAT DECREASES NICKEL TOXICITY IN SEEDLINGS

A plant growth-promoting bacterium, Kluyvera ascorbata SUD165, that co ntained high levels of heavy metals was isolated from soil collected n ear Sudbury, Ontario, Canada. The bacterium was resistant to the toxic effects of Ni2+, Pb2+, Zn2+, and CrO4-, produced a siderophore(s), an d displayed 1-aminocyclopropane-1-carboxylic acid deaminase activity. Canola seeds inoculated with this bacterium and then grown under gnoto biotic conditions in the presence of high concentrations of nickel chl oride were partially protected against nickel toxicity. In addition, p rotection by the bacterium against nickel toxicity was evident in pot experiments with canola and tomato seeds. The presence of K. ascorbata SUD165 had no measurable influence on the amount of nickel accumulate d per milligram (dry weight) of either roots or shoots of canola plant s. Therefore, the bacterial plant growth-promoting effect in the prese nce of nickel was probably not attributable to the reduction of nickel uptake hy seedlings. Rather, it may reflect the ability of the bacter ium to lower the level of stress ethylene induced by the nickel.