Developing Growth Promotion Strategies for Cressa truxillensis to Improve Success of Restoration Activities

Abstract. Cressa truxillensis, commonly known as alkali weed, is native to western North America and is used in revegetation projects in saline or alkaline soils at locations such as the Ballona Wetlands Ecological Reserve. This research aimed to (i) determine methods to improve C. truxillensis seed germination, (ii) characterize the impact salt has on seed germination and growth, and (iii) identify and characterize bacterial seed endophytes and their potential as plant growth promoting bacteria (PGPB). Results showed that seed scarification, either through mechanical or chemical methods, substantially improved seed germination rates. The presence of salt at 300 mM NaCl delayed germination, and both 150 mM and 300 mM NaCl decreased seedling size. Two different strains of Paenibacillus peoriae were found to reside within C. truxillensis seeds collected from the Ballona Wetlands. Although neither strain alleviated the salt sensitivity displayed by C. truxillensis, both strains showed tolerance to heavy metals, salt, and showed additional properties suggestive that they may function as PGPB. Methods used in this study can serve as guidelines for preparation of seed of C. truxillensis prior to seeding in appropriate habitats throughout the species' range.