Mechanisms of improving nitrogen uptake, utilization and grain yield of wheat population with high radiation use efficiency

Objectives We constructed different types of radiation use efficient populations through the plant densities of wheat, and compared their N accumulation and transport characteristics before anthesis and the N accumulation after anthesis, to provide a theoretical base for improving wheat yield through efficient radiation use efficiency (RUE).

Methods Field trials were conducted in Suixi and Mengcheng counties of Anhui Province in 2018−2019, the cultivar “An 1302” with strong tillering ability and “Wankenmai 0622” with weak tillering ability were employed as the test materials. Four plant densities: 180×10⁴ plants/hm² (D1), 240×10⁴ plants/hm² (D2), 300×10⁴ plants/hm² (D3), and 360×10⁴ plants/hm² (D4) were set up for the investigation of yield, and the interception rate, amount, and photosynthetic conversion efficiency of active radiation at milk-ripening stage. According to these data, the wheat population was divided into high, moderate and low radiation use efficient types, denoted as H-, M-, and L-RUE, respectively. The N accumulation and translocation during anthesis stage, and the N accumulation and leaf area index at milk-ripening stage were compared among the three population types.

Results Cultivar, density and their interaction significantly affected the RUE and grain yield. The RUE and grain yield of H-RUE population were 1.4% and 9.7 t/hm², which were higher than those of M- and L-RUE by 5% and 14%, 1% and 5%, respectively. The interception rate at anthesis and milk-ripe stages, and the interception amount of available radiation from anthesis to milk-ripe stages were not significantly different among the three population types, but the photosynthetic conversion efficiency of H-RUE was 2.34 g/MJ, which was higher than that of M- and L-RUE population. The H-RUE population had a higher leaf area index at anthesis (7.24) and milk-ripe stages (4.53), and higher N accumulation in stem & leaf sheath (63.9 kg/hm²), leaves (79.5 kg/hm²), and per unit leaf area (143.78 μg/cm²) at anthesis, compared to the other population types. In addition, H-RUE population and the individual stem had similar translocation rate of N at pre-anthesis stage with the M- and L-RUE populations and the individual stems, but had significantly higher N translocation amount due to their higher N accumulation amount. The leaf area index of H-RUE population was significantly higher than the M- and L-RUE populations at anthesis and milk-ripening stage as well.

Conclusions The wheat population with high radiation use efficiency could accumulate more N in stems & leaf sheaths, and leaves, and has higher N accumulation amount per unit leaf area before anthesis stage, in spite of higher translocation amount of N, the N accumulation in the vegetative organs is higher than those in the moderate and low radiation use efficiency populations, so the population maintains high leaf area index at anthesis and milk-ripening stage, which is inductive to the radiation conversion and the formation of yield.