Data from: Growth of maize on mixed nitrate and ammonium promotes auxin synthesis and biomass accumulation

Mixed nitrate (NO3-) and ammonium (NH4+) as nitrogen source can improve
plant growth. The underlying mechanism was explored by using metabolomics
and transcriptome. Maize plants were grown hydroponically with three
nitrogen forms (nitrate, 75/25 nitrate/ammonium and ammonium). Mixed N
increased photosynthetic rate compared to nitrate supply, and had the
highest leaf area, shoot and root biomass among the three nitrogen
treatments. In shoot and root, the concentration of nitrogenous compounds
(NH4+, Gln, Asn) and carbohydrates (sucrose, glucose, fructose) in plant
with mixed N supply was higher than that with nitrate supply, but lower
than that with ammonium supply. The activity of the related enzymes (GS,
ASNS, PEPCase, invertase, AGPase) changed accordingly. Specifically, mixed
N enhanced IAA synthesis via shikimic acid pathway, as indicated by the
higher PEP and tryptophan compared to the other two treatments. The
expression of corresponding genes involving IAA synthesis and response
were up-regulated. Sole ammonium supply resulted in high level of Gln and
Asn, starch, and T6P. It is concluded that, in addition to increase
photosynthesis, mixed N supply enhances leaf growth via increasing IAA
synthesis to build a big sink for C and N utilization, which, in turn,
facilitates further C assimilation and N uptake.