Abstract: Taking super high-yielding wheat cultivar Jimai 22 as test material, a field experiment was conducted to study the effects of combined application of nitrogen (N) and phosphorus (P) on the diurnal variation of photosynthesis at grain-filling stage and the grain yield of the cultivar. In treatments CK (without N and P application) and low N/P application (225 kg N ·hm^-2 and 75 kg P ·hm^-2), the diurnal variation of net photosynthetic rate (P_n) was presented as double-peak curve, and there existed obvious midday depression of photosynthesis. Under reasonable application of N/P (300 kg N·hm^-2and 150 kg P ·hm^-2, treatment N₂P₂), the midday depression of photosynthesis weakened or even disappeared. Stomatal and non-stomatal limitations could be the causes of the midday depression. Increasing N and P supply increased the P_n, stomatal conductance (G_s), stomatal limitation value (L_s), and transpiration rate (T_r). Fertilizer P had less effects on the photosynthesis, compared with fertilizer N. When the P supply was over 150 kg·hm^-2, the increment of P_n was alleviated and even decreased. Among the fertilization treatments, treatment N₂P₂ had the highest P_n, G_s, and water use efficiency, being significantly different from CK. It appeared that fertilizer N had greater regulatory effect on the diurnal variation of photosynthesis, compared with fertilizer P, while the combined application of N and P had significant co-effecton the P_n, G_s, and T_r. A combined application of 300 kg N ·hm^-2 and 150 kg P ·hm^-2 benefited the enhancement of P_n and grain yield.

Key words: combined application of nitrogen and phosphorus, super high-yielding winter wheat, diurnal variation of photosynthesis, yield, fuel, thermogravimetric analysis, flammability, combustibility, sustainability., ignitibility