Abstract: A field plot experiment was conducted in the farm of Henan Agricultural University in 2006-2007 to examine the effects of row and plant spacing on the flag leaf sucrose metabolism and grain yield of winter wheat. Five ratios of row spacing to plant spacing, i.e., 1.5 (RP1), 3.4 (RP2), 6.0 (RP3), 10.5 (RP4), and 15.0 (RP5), were installed in a randomized block design with three replicates. The sucrose synthase (SS) and sucrose phosphate synthase (SPS) activities and soluble sugar and sucrose contents in flag leaves and the grain filling rate all showed a single peak variation with grain filling. Flag leaf SS and SPS activities and sucrose content increased with increasing row spacing but decreased with decreasing plant spacing, with the optimum in treatment RP3, which suggested that an appropriate row and plant spacing could effectively promote the allocation of photosynthates and their transformation into sucrose, supplying enough carbon assimilates for grain filling. The soluble sugar content in flag leaves in treatment RP3 was higher at early grain filling stage and had a relatively slow decrease at mid and late grain filling stages, compared with that in other treatments. In addition, the peak grain filling in treatment RP3 came later, and sustained a longer period with lower filling rate at early filling stage and with higher filling rate at late filling stage, keeping at 0.28 mg·d^-1 28-35 days after anthesis. The ear number, grain number per spike, and 1000-grain weight increased with increasing row spacing but decreased with decreasing plant spacing. Treatment RP3 had the harmonized yield-composing factors and the highest grain yield. Therefore, to reduce row spacing, enlarge plant spacing, and keep an appropriate ratio of row spacing to plant spacing would be an alternative in winter wheat planting.

Key words: Paddy field, NH₄⁺, NH₃^-, Total N, Dynamic feature, Simulation