在大田条件下，以豫麦34为试材，研究了2个施氮水平（330和240 kg .hm-2）下施用纯硫0、60、100 kg.hm-2对小麦旗叶氮、硫同化关键酶活性及其产量的影响。结果表明，两种氮素水平下施硫对小麦旗叶中硝酸还原酶（NR）、谷胺酰氨合成酶（GS）、谷氨酸-丙酮酸转氨酶（GPT）活性均有影响。高氮水平下随施硫量的增加NR活性降低，GS活性提高，GPT活性在灌浆中期也表现出与GS活性相同的趋势，中氮水平下表现为随施硫量的增加NR活性提高，GS活性S60处理显著高于其他处理，GPT活性不同施硫处理间差异不明显。表明高氮条件下施硫抑制了NR活性，但提高了GS、GPT活性，中氮条件下施硫提高了NR和GS活性。两种氮素水平下乙酰丝氨酸水解酶（OASS）活性均随施硫量的增加而降低，尤其高氮和低硫条件下OASS活性升高。两种施氮水平下干物质积累量均随施硫量的增加而提高。氮和氮硫互作对籽粒产量的影响达到显著水平，硫对籽粒产量的影响达到极显著水平，两种氮素水平下均随施硫量的增加而提高，N330水平显著低于N240水平，N330水平下S100和S60 与对照相比达显著水平，N240水平下，施硫处理籽粒产量均显著高于对照。两种氮素水平下施硫处理千粒重均较对照显著提高，但穗数和穗粒数差异不显著，无论何种施氮水平下，千粒重提高是产量增加的主要原因。
Sulphur (S) deficiency has become a marked problem in agricultural system in many regions in the last two decades, and sulphur application in S-deficiency soils may increase crop yield and improve the grain quality. In plants, there is a close relationship between sulphur and nitrogen. Crop response to S fertilizer often depends on the amount of N supply. Deficiency of S may be induced by a high nitrogen amount, and responses to S application are usually greater when abundant nitrogen fertilizer applied. Although wheat has a relatively low requirement for S, deficiency of S in wheat growth has been observed in many regions in China. Previous studies have focused on effects of single S fertilizer on growth and yield of wheat. We took a strong-gluten wheat (Triticum aestivum L.) cultivar Yumai 34 as experimental material to explore the activities of key enzymes for nitrogen and sulphur assimilation and the response of grain yield to different fertilizer applications of sulphur and nitrogen. The experiment was conducted in the soil with available sulphur content of 22.78 mg kg-1 in 2003/2004 and 2004/2005 growing seasons by split plot design. The main plot was two nitrogen levels with 330 (N330) and 240 (N240) kg ha-1, respectively, and the subplot was three sulphur levels with 0 (S0), 60 (S60), and 100 (S100) kg ha-1, respectivly. The results indicated that sulphur fertilizer could improve the activities of nitrate reductase (NR), glutamine synthetase (GS), and glutamic-pyruvic transaminase (GPT), which are the key enzymes of nitrogen assimilation, and may be speculated to improve the nitrogen assimilation ability. But, under different nitrogen application levels, the amount of sulphur needed was different. In N330 treatment, sulphur application could reduce NR activity and improve GS and GPT activities. In N240 treatment, 0 sulphur application could improve NR and GS activities. The activity of o-acetylserine thiollyase (OASS), a key enzyme of sulphur assimilation, reduced with inreasing of sulphur application rate. Furthermore, OASS activity enhanced under high N-supply and S-deficiency conditions. The effects of N and its interaction with S on grain yield were significant (P<5%) , and those of S were highly significant (P<1%). Under the both nitrogen levels of N330 and N240, dry matter accumulation of S application treatments increased significantly as compared with that of control (S0), and the grain yield of N330S100, N330S60, N240S100, and N240S60 treatments rose by 28.6% (P＜0.01), 12.6% (P＜0.05), 25.7% (P＜0.01), and 25.3% (P＜0.01) respectively. The 1000-grain weight of sulphur treatments significantly increased at both nitrogen levels, but the spike number and grains per spike had no significant difference among the treatments.
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