Biological nitrogen fixation in soybean under water restriction and exposed to 1-methylcyclopropene

The objective of this work was to assess the effects of 1-methylcyclopropene (1-MCP) on traits related with biological nitrogen fixation on 'BRS 268' soybean (Glycine max) subjected to water restriction. Plants were either exposed to drought between 32 (R-2) and 47 (R-3) days after sowing (DAS) or kept well-watered, in combination with exposure or not to 1-MCP. On the second day under drought (34 DAS), plants from both water conditions were exposed to 1-MCP in a hermetically sealed chamber for 15 hours. Control plants, dry or well-watered, that were not exposed to 1-MCP were kept in a separate chamber. At 36 (R-2) and 47 (R-3) DAS, shoot and root dry weights, leaf area index, number and dry weight of nodules, total ureides in sap, and N concentration in leaves were assessed. From 47 DAS on, extra plants were well watered until physiological maturity (R-8) and assessed for yield components. Water restriction increased ureides in sap and reduced N in leaves in R-2; reduced the number and mass of nodules, shoot dry weight, and leaf area index in R-3; and reduced the number of pods and seed mass of plants not exposed to 1-MCP. However, when plants are exposed to 1-MCP, there is an attenuation of water restriction effects.