Impact of Nitrogen Availability on the Accumulation of Vegetative Lipids in Sorghum

Authors

Leticia Felicio Pasqualino, University of Nebraska - LincolnFollow

First Advisor

Thomas Clemente

Second Advisor

Jeffrey Mower

Date of this Version

6-2023

Comments

A Thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science, Major: Agronomy (Plant Breeding and Genetics), Under the Supervision of Professor Thomas Clemente and Jeffrey Mower. Lincoln, Nebraska: June 2023

Copyright © 2023 Leticia Felicio Pasqualino

Abstract

Sorghum (Sorghum bicolor (L.) Moench) is a versatile and prosperous feedstock crop for renewable energy production. With the increase in bioenergy demand, the production of higher oil content per biomass in a feedstock crop is a highly desirable trait for the biofuel conversion process yield. Especially if this outcome can be achieved using fewer inputs in the field, such as nitrogen. In microalgae species, nitrogen limitation has been associated with changes in the carbon storage metabolic pathway favoring triacylglycerol (TAG) accumulation. In this context, this study aimed to assess whether nitrogen starvation would result in a similar outcome in higher plants. Nitrogen limitation's impact on sorghum vegetative lipids accumulation was investigated in two sorghum genotypes. In a soilless trial, greenhouse-grown plants were submitted to three levels of nitrogen supply: 0.0 mM, 0.75 mM, and 15 mM KNO₃ delivered in nitrogen-free Hoagland's liquid solution. Total fatty acids (TFA), TAG and biomass were analyzed in three developmental stages (7-leaf, flowering, and post-flowering). At the 7-leaf stage, lower nitrogen availability resulted in significantly higher TAG content, where the values for 0.0, 0.75, and 15 mM N treatments were 0.97, 0.72, and 0.44 TAG %DW, respectively (P=0.04). The same results pattern was observed at the flowering stage, where lower nitrogen resulted in 1.24 TAG %DW, while higher nitrogen resulted in 0.78 TAG %DW. Post-flowering TAG content did not present a significant difference across nitrogen treatments. The TFA content increased with nitrogen availability, and the nitrogen treatment effect was significant at the flowering (PP=0.02) stages. Across all stages, biomass was significantly higher with increased nitrogen availability. The research findings are initial steps in comprehending the impact of nitrogen availability on sorghum vegetative lipids and provide valuable insights for optimizing the balance of nitrogen application and biomass yield ratio to achieve valuable and sustainable sorghum production for biofuel feedstock.

Advisors: Thomas Clemente and Jeffrey Mower