Student: Samantha Darling
Mentor: Mary Poulson
Winter wheat (Triticum aestivum L.) is of huge importance to global agriculture. Wheat is sown in the fall, germinates and then goes dormant to resume growth in the spring. Although winter wheat strains are bred to tolerate gradual changes in temperature, unexpected frosts in the spring can potentially cause cellular damage and decreased growth rates for young plants. Plant growth promoting bacteria (PGPB) have been shown to play an integral role in increasing plant tolerance to drought, salinity and pathogens but effects of PGPB on plant cold hardiness has not yet been well documented. In this project, young wheat plants were inoculated with three PGPB strains shown to enhance plant stress tolerance: Pseudomonas fluorescens, Bacillus subtilis and Paenibacillus polymyxa. After germination and a short growth period at 21oC, plants were exposed to cold (5oC or 12oC) salt (100 mM NaCl) or drought (25% of water given to control plants). Plant productivity was determined by measuring total plant biomass and freezing tolerance was assessed by measuring ion leakage from cells after freezing. Growth of plants was reduced by nearly 50% for plants at 12oC or 5oC. Salt did not affect plant growth. Drought reduced plant fresh weight by 40% but only 10% dry weight. PGPB did not affect plant growth or susceptibility to freezing tolerance for salt or drought plants. For plants not previously exposed to cold stress, however, inoculation with P. polymyxa did lend some protection from freezing stress.