Abstract:

Aims The biosynthesis of maize protein, which is positively correlated to maize grain quality, is controlled by nitrate reductase (NRase), glutamine synthetase (GS), and glutamate dehydrogenase (GDH), which are affected by genetics and environment. Therefore, cultivation methods and environment affect grain quality in maize; however, there are few reports of the effects of soil water on maize grain quality and corresponding enzyme activities.
Methods The experiment was carried out in pool culture within a rain-proof shelter using normal maize (Yedan 22) and high oil maize (Gaoyou 115). There were three water treatments: no irrigation after anthesis, irrigation once after anthesis (at grain filling period) and irrigation three times after anthesis (at grain filling period, milky period and wax period).
Important findings Grain protein was higher in Gaoyou115 than Yedan22, and its component contents increased with increasing water supply. With different water supply, the activities of NRase, GS in leaves and GS, GDH in grains exhibited the same trends in the two types of maize. The activity of NRase decreased, and the activities of GS and GDH had unimodal curves, peaking 20 to 40 days after pollination. The activities of these enzymes increased with increased water supply. However, the activity of NRase in leaves of Yedan22 was higher than in Gaoyou115, while the activities of GS in leaves and GDH in grains were reversed, resulting in lower protein content in grains of Yedan22 than in Gaoyou115. The NRase and GS activities in maize leaves did not match grain protein content. Soil water condition was closely related with the activities of GS and GDH in ear leaves and grains of different types of maize.

Key words: water, maize, variety type, protein, enzyme