Abstract
Non-structural carbohydrates (NSC) play an important role in yield formation. In this paper, the relationships of NSC accumulation and translocation with yield formation were investigated under elevated CO2 concentrations ([CO2]) and nitrogen (N) application rates. A japonica rice (Oryza sativa L.) cultivar, “Nanjing 9108,” was grown at three [CO2]—Ambient (T0), ambient + 160 μmol·mol−1 (T1), and ambient + 200 μmol·mol−1 (T2)—in open-top chambers (OTC), with three levels of N fertilizer application rates—10 gN·m−2 (N1), 20 gN·m−2 (N2), and 30 gN·m−2 (N3)—Which were set in OTCs using pot experiments. The results showed that the concentration of NSC (CNSC) and the total mass of NSC stored in stems (TMNSC) under T1 and T2 were higher than those in the T0 treatment, and the CNSC and TMNSC of N3 were lower than those of N1 and N2 at the heading stage. The CNSC and the TMNSC were significantly positively correlated with the stem biomass during the growth period and were notably negatively correlated with the N content in leaves (Nleaf) at the heading and filling stages. The seed setting rate was significantly positively related to the apparent transferred mass of NSC from stems to grains (ATMNSC) at the filling stage, while the relationship between yield and the ATMNSC was not statistically significant. Although there was no difference in the apparent contribution of transferred NSC to grain yield (ACNSC) between treatments, NSC stored in stems further accumulated obviously during the late filling stage, implying that the grain yield of “Nanjing 9108” was predominantly sink-limited. We concluded that elevated [CO2] improved the concentration of NSC at the rice heading stage. The interaction between elevated [CO2] and N fertilizer rates significantly influenced the concentration of NSC at the filling stage. Rice stems NSC reaccumulated at the late grain filling stage, which implies a restriction on NSC transference to grain.
Highlights
With the rapid development of the world’s industry and economy, the CO2 concentration ([CO2]) has increased from 278 μmol·mol−1 before the industrial revolution to 414 μmol·mol−1 [1] and is predicted to reach 538–670 μmol·mol−1 in 2100 under the greenhouse gas emission stabilization scenario [2]
Referring to Li et al [18], Pan et al [20], and Wu et al [40], the total mass of Non-structural carbohydrates (NSC) stored in stems (TMNSC, g) was calculated as stem biomass multiplied by the corresponding concentration of NSC (CNSC)
We identified the impact of elevated [CO2] and nitrogen application on NSC accumulation and transferation in rice, the contribution of NSC in stem to grain before heading was evaluated only by the difference of NSC accumulation between heading and maturity
Summary
With the rapid development of the world’s industry and economy, the CO2 concentration ([CO2]) has increased from 278 μmol·mol−1 before the industrial revolution to 414 μmol·mol−1 [1] and is predicted to reach 538–670 μmol·mol−1 in 2100 under the greenhouse gas emission stabilization scenario [2]. In the past ten years, the annual growth in rice yield has fallen below 1% and is virtually nil in Asia [11] Abiotic stresses, such as drought, flooding, and abnormal temperatures challenge current and future global rice production [8,12,13,14]. NSC stored in stems before heading can be translocated into the panicle to supply grain filling [17,18], which contributes 1–30% to yield [19,20]. Low N application increased stem NSC accumulation before the heading stage and NSC translocation during the grain filling stage, and increased the seed setting rate of superior spikelets [18]. Excessive N application delayed plant senescence, further reducing NSC translocation from stems to grains [31]
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