Figure 4.

Relationship between relative N mobilization rate and the apparent efficiency of mobilized pre-anthesis protein-C utilization for deposition of grain proteins (ME_P) (A) and the relative contribution of pre-anthesis C to grain carbohydrate-C (B). Relative N mobilization rate was calculated as the N mobilization per day during the first 16 d after anthesis relative to total N mobilization between anthesis and maturity. ME_P was defined as the mass of pre-anthesis C deposited in grain protein relative to the mass of pre-anthesis protein-C mobilized in aboveground vegetative plant parts between anthesis and maturity (g g⁻¹). Pre-anthesis C deposition in grain proteins of main tiller ears was assessed by long-term steady-state ¹³CO₂/¹²CO₂ labeling. The wheat cultivars Kadett (▵, ⋄) and Star (○, □) were grown with differential N fertilizer supply (low-N, black symbols; high-N, white symbols) in 1991 (▵, ○) and 1992 (⋄, □).