Abstract
In this study, field-grown wheat (Triticum aestivum L.) was treated with normal (Nn) and excessive (Ne) levels of fertilizer N. Results showed that Ne depressed the activity of superoxide dismutase and peroxidase and increased the accumulation of reactive oxygen species (ROS) and malondialdehyde. The normalized difference vegetation index (NDVI) was higher under Ne at anthesis and medium milk but similar at the early dough stage and significantly lower at the hard dough stage than that under Nn. The metabolomics analysis of the leaf responses to Ne during grain filling showed 99 metabolites that were different between Ne and Nn treatments, including phenolic and flavonoid compounds, amino acids, organic acids and lipids, which are primarily involved in ROS scavenging, N metabolism, heat stress adaptation and disease resistance. Organic carbon (C) and total N contents were affected by the Ne treatment, with lower C/N ratios developing after medium milk. Ultimately, grain yields decreased with Ne. Based on these data, compared with the normal N fertilizer treatment, we concluded that excessive N application decreased the ability to scavenge ROS, increased lipid peroxidation and caused significant metabolic changes disturbing N metabolism, secondary metabolism and lipid metabolism, which led to reduced grain filling in wheat.
Highlights
Dependent on plant N status and soil N content[12]
The present study was conducted in a wheat field in northern China, and the objectives were to investigate the effects of excessive N on the differential metabolism and senescence-related physiology of wheat to increase our understanding of the responses of this crop to an environment with excess N
After anthesis (Zadoks 69), ROS increased and peaked at early dough (Zadoks 83) in flag leaves of N treatment (Ne) wheat (Fig. 1), whereas in flag leaves of N treatment (Nn) wheat, a relatively stable ROS level was maintained during the periods of anthesis and early dough, which was followed by a significant increase at maturity stage
Summary
Dependent on plant N status and soil N content[12]. a better understanding of the detrimental effects of excessive N and the synchronization of N application with actual crop demand will offer a new strategy for grain development based on the regulation of programmed senescence. Many metabolomics studies have been conducted in cereal crops such as rice[14,15], maize[16], barley (Hordeum vulgare L.)[17,18], foxtail millet (Setaria italica L.)[19], and bread and durum wheat[20,21] These studies focused primarily on the metabolite profiling of plants subjected to stress such as heat, drought and nutrient deficiency to assess the effects of environmental factors on profile characteristics. Despite the agronomic importance of wheat, little experimental information is available for physiological and metabolite changes of the flag leaf (the primary source of assimilates for grain growth) of wheat in response to excessive N during grain development Providing this information is essential in China because many farmers apply excessive N rather than synchronizing N supply with crop demand[23,24]. The present study was conducted in a wheat field in northern China, and the objectives were to investigate the effects of excessive N on the differential metabolism and senescence-related physiology of wheat to increase our understanding of the responses of this crop to an environment with excess N
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