Abstract
BackgroundIncreasing atmospheric [CO2] can increase photosynthesis and promote plant growth, consequently influencing nitrogen (N) cycling. Yet, there is no systematic information on the N response among different organs of japonica and indica rice genotypes to elevated [CO2] as affected by N application. To investigate the impacts of elevated [CO2] and N fertilization on N uptake and utilization of different genotypic rice (Oryza sativa L.) during grain filling, a free-air CO2 enrichment (FACE) experiment with indica cv. Liangyou 084 (IIY084) and japonica cv. Wuyunjing 23 (WYJ23) was conducted in Eastern China. Crops were exposed to ambient [CO2] and elevated [CO2] (200 μmol mol−1 above ambient) at two levels of N: control (0N) and 22.5 g N m−2 (normal N, NN), and they were sampled at 82 days after transplanting (DAT), 99 DAT, and maturity, respectively.ResultsUnder FACE, significant declines of N concentration in all tissues and the whole plants were observed with the greater decrease in leaves and stems at three stages. Positive responses of N use efficiency (NUE) to elevated [CO2] were recorded over the study period. The total N accumulation remained unchanged, while a large amount of N was partitioned to panicles at the expense of leaves and stems. As compared to WYJ23, greater N transportation from roots to aboveground, especially the panicles, was observed on IIY084 accompanied by higher panicle biomass (82 DAT and 99 DAT), N concentrations (maturity), and greater NUE for leaves through the study season. Across all [CO2] and cultivars, N fertilization increased N partitioning to leaves and stems while decreasing that to panicles. Additionally, N supply decreased NUE while stimulating N concentrations and N amounts of rice plants. Among all treatments, IIY084 had the highest N accumulation and allocation in panicles under elevated [CO2] in combination with N fertilizer at maturity.ConclusionData from this study were helpful for understanding the temporal N uptake and utilization of different rice genotypes as affected by N availability and suggest that IIY084 promises a considerable prospect for its grain yield and quality under future elevated atmospheric [CO2].
Highlights
Due to the activities of human beings, such as the increasing demands for cultivated lands and energies, global atmospheric [Carbon dioxide (CO2)] is increasing from 280 μmol mol−1 before industrial revolution to 402 μmol mol−1 in recent years
Biomass of roots was consistently higher at the elevated [CO2] across all cultivars and N levels with average increase of 27.7, 19.4, and 18.1% at 82 days after transplanting (DAT) (P < 0.01), 99 DAT (P < 0.05), and maturity (P < 0.1), respectively (Tables 1 and 2)
indica cv. Liangyou 084 (IIY084) had greater panicle biomass and N concentrations since more N was transferred from roots to aboveground, especially the panicles
Summary
Due to the activities of human beings, such as the increasing demands for cultivated lands and energies, global atmospheric [CO2] is increasing from 280 μmol mol−1 before industrial revolution to 402 μmol mol−1 in recent years. Nitrogen (N), accounting for 1–3% of the whole plant, is one of the essential elements required for plant growth and yield as well as quality and may play a critical role in the responses of plants to elevated [CO2] (Kim et al 2003). Based on both area and tonnage harvested, rice (Oryza sativa L.) is one of the most important crops in the world and the first food in Asia, providing dietary needs to a large population. Crops were exposed to ambient [CO2] and elevated [CO2] (200 μmol mol−1 above ambient) at two levels of N: control (0N) and 22.5 g N m−2 (normal N, NN), and they were sampled at 82 days after transplanting (DAT), 99 DAT, and maturity, respectively
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