Electronic Thesis and Dissertation Repository


Master of Science




Sheila M Macfie


I investigated plant-microbe-metal interactions under metal stress. In theory, plant growth promoting rhizobacteria (PGPR) promote plant growth by reducing stress ethylene and synthesizing indole-3-acetic acid (IAA). The putative PGPR Pseudomonas fluorescens UW4 and a mutant strain that lacked an enzyme critical to the reduction of plant ethylene were studied to determine if they could promote Arabidopsis thaliana growth under cadmium and copper stress conditions. Both strains of P. fluorescens UW4 adhered to roots and synthesized IAA, and the wild-type lowered metal stress-induced ethylene in Arabidopsis, but neither strain enhanced plant growth. Wildtype P. fluorescens UW4 and its mutant had no effect on altering the concentrations of other plant stress hormones with the exception of salicylic acid under copper stress. More work is needed to determine why P. fluorescens UW4 did not promote growth under metal stress conditions before it can be utilized in agricultural settings.

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