Metabolomics analysis reveals the physiological mechanism underlying growth restriction in maize roots under continuous negative pressure and stable water supply

Metabolomics analysis was used to elucidate the mechanism underlying response of the maize root system to continuous negative pressure and stable water supply. Results showed a significant reduction in continuous negative pressure and stable water supply (NPI) relative to intermittent positive pressure water supply (DI), maize root dry matter accumulation and root shoot ratio in NPI was 20.22%, 34.15% and lower than DI, respectively, yield was 44.10% higher than DI, and superoxide anion, malonic dialdehyde, osmotic adjustment substance content, and antioxidant enzyme activity was reduced. Next, we applied liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry, and nuclear magnetic resonance to perform non-targeted metabolomics analysis with the aim of elucidating the physiological basis of root redundant growth restriction. Results revealed presence of 33 different metabolites in NPI, belonging to different categories, including organic acids and their derivatives, nucleosides, nucleotides and their corresponding analogues, lipids and lipid-like molecules, as well as organic oxygen compounds. Moreover, all these were enriched in 44 metabolic pathways, relative to DI. Notably, metabolic pathways, biosynthesis of secondary metabolites, starch and sucrose metabolism, plant hormones biosynthesis, and biosynthesis of plant secondary metabolites might restrict maize roots growth. In NPI was, Trehalose, 2'-deoxyadenosine, isoleucine and ajmaline were 0.34-, 0.05-, 0.004- and 0.17-fold lower than DI, whereas glutamic acid, glutamine and zeatin were 4.62,4.26,4.06 times higher than DI. This might inhibit root redundant growth. In summary, continuous negative pressure and stable water supply inhibited maize root redundant growth restriction by suppressing sugar metabolism and protein synthesis via genetic information transmission.