Azospirillum inoculation mitigates water stress effects in maize seedlings

Water stress in maize (Zea mays, L) after planting slows down germination and initial seedling growth. This study determined that seed inoculation with Azospirillum brasilense BR11005 could mitigate negative water stress effects in seedlings. Pots containing a mixture of sand and vermiculite were divided in three lots and irrigated with a nutrient solution, to 200 g moist kg(-1) bed dry weight (HM), 100 g kg(-1) bed dry weight (MM), or to 50 g kg(-1) bed dry weight (LM), respectively. The first lot corresponded to well irrigated pots and the other two, to 50% and 75% water supply reduction, resqectively. Hybrid DK 636 maize seeds were treated during imbibition with either 10 live or autoclaved (control) A. brasilense cells seed(-1), pre-germinated in a humid chamber, and planted in the pots. All seedlings were then grown in a greenhouse at their corresponding water regimes, for up to 15 d after planting. Total aerial biomass (TAB) and foliar area (FA) was determined in shoots. Relative water content (RWC), water content (WC), and water potential (T) were determined in leaves. Free proline concentration was determined in both leaves and roots. In addition, surface and dry weight (DW) were determined in roots. Seed inoculation with Azospirillum improved both leaf RWC and WC, prevented a significant T drop in leaves, increased root growth, TAB and FA, and promoted proline accumulation in both leaves and roots, in seedlings grown for 15 d at 75% water supply reduction.