Molecular mechanism of negative pressure irrigation inhibiting root growth and improving water use efficiency in maize

This study assessed the effect of stable soil water content on root growth and water use efficiency in maize under a negative pressure irrigation system. A two-year pot experiment for maize was carried out under negative pressure irrigation and drip irrigation. The root growth characteristics and water use efficiency by the maize was evaluated. In addition, transcriptome sequencing was conducted to explore the pathways and genes that respond to variations in soil water content. Negative pressure irrigation more effectively increased the accumulation of above-ground dry matter and root vitality compared to drip irrigation but it reduced the accumulation of root dry matter, and root-shoot ratio. Negative pressure irrigation also reduced levels of superoxide anion, malondialdehyde, proline, soluble protein, and soluble sugar contents, and the activities of superoxide dismutase, peroxidase, catalase and polyphenol oxidase. It was also observed that genes involved in starch and sucrose metabolism, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, glycolysis/gluconeogenesis pathways, were downregulated under negative pressure irrigation which suppressed root growth. Three GO terms, channel activity, water transport, and water channel activity, were highly enriched under negative pressure irrigation. Thirteen genes related to water absorption and transport such as ZM00001D003006 and ZM00001D014285 were significantly up-regulated. Negative pressure irrigation improved the water use efficiency by maize crops and inhibited root growth. Zm00001d024891 and Zm00001d003190 were found to be associated with root growth, whereas ZM00001D003006 and ZM00001D014285 participated in the control of water absorption and water use efficiency.