不同氮效率水稻品种叶片光合作用及氮利用特征的差异分析

以扬稻6（氮高效品种）、武玉粳3（氮低效品种）为材料,在含有2.86mmol/L NH₄ ⁺溶液培养条件下,分别在开花期和灌浆期分析了中位叶、旗叶的净光合速率、氮同化酶的活性、叶片氮含量与转移率以及对子粒的贡献。结果表明：（1）旗叶的净光合速率显著高于中位叶;扬稻6旗叶的净光合速率显著高于武玉粳3,而中位叶净光合速率在品种间差异不显著。（2）硝酸还原酶活性（NRA）、谷氨酰胺合成酶活性（GSA）是中位叶高于旗叶、灌浆期高于开花期、扬稻6高于武玉粳3。从开花到灌浆期,旗叶可溶性糖含量呈增加的趋势,而中位叶可溶性糖含量呈减少的趋势。旗叶可溶性糖含量高于中位叶、扬稻6高于武玉粳3。可溶性蛋白含量呈下降的趋势,扬稻6可溶性蛋白含量高于武玉粳3。扬稻6、武玉粳3中位叶可溶性蛋白的转出率分别是50.3%、37.6%;旗叶可溶性蛋白的转出率分别是69.5%、44.4%。（3）中位叶总氮积累量显著高于旗叶、开花期显著高于灌浆期。扬稻6中位叶、旗叶氮转移量分别为35.6%、34.7%;武玉粳3中位叶、旗叶氮转移量分别为26.9%、35.3%。（4）去除中位叶,子粒氮分别比对照减少了6.9%（扬稻6）、4.6%（武玉粳3）;子粒产量分别比对照减少了7.3%（扬稻6）、4.9%（武玉粳3）。去除旗叶,子粒氮分别比对照减少了10.5%（扬稻6）和9.2%（武玉粳3）;子粒产量分别比对照减少了13.8%（扬稻6）、11.1%（武玉粳3）,表明旗叶对子粒氮和产量的贡献更大。总之,氮高效品种旗叶光合作用和氮同化能力显著高于氮低效品种,另一方面,其中位叶储存的氮也能及时转移到子粒中,提高了氮效率,这反映了不同氮效率品种氮素利用差异的机制。

Differences in Leaf Photosynthesis and Assimilation of Nitrogen Between Two Rice Cultivars Differing in Nitrogen Use Efficiency

Two rice cultivars,Yangdao 6 (a cultivar with high N use efficiency) and Wuyujing 3 (a cultivar with low N use efficiency) were hydroponically grown in nutrient solutions containing 2.86mmol/L NH₄ ⁺. Several physiological indexes in mid-position and flag leaves, such as net photosynthetic rate, the activities of glutamine synthetase (GS) and nitrate reductase (NR), content of soluble sugar and protein, content and transition of N and its contribution to grain N accumulation and yields were conducted. The results were as follows: (1) Net photosynthetic rate of flag leaves were always higher than that of mid-position leaves at the stage of anthesis or grain filling. As for cultivars, net photosynthetic rate of flag leaves in Yangdao 6 was significantly higher than that in Wuyujing 3 (P<0.05), while it showed no significant differences between the mid-position leaves at the stage of anthesis. Furthermore, it was higher in flag leaves than that in mid-position leaves and higher in Yangdao 6 than that in Wuyujing 3. (2) NRA and GSA were higher in mid-position leaves than that in flag leaves and were higher at grain filling stage than at anthesis stage. Also, they were significantly higher in Yangdao 6 than that in Wuyujing 3. From flowering to grain filling stage, content of soluble sugar exhibited increase in flag leaves while decrease in mid-position leaves, respectively. Content of soluble protein decreased, and it was higher in Yangdao 6 than that in Wuyujing 3. The transported soluble protein in mid-position and flag leaves in Yangdao 6, Wuyujing 3 were 50.3%, 37.6% and 69.5%, 44.4%, respectively. (3) Total N accumulation in mid-position leaves was higher than that in flag leaves and was higher at anthesis stage than at grain filling stage. As for cultivars, the amount of total N accumulation and transition in mid-position and flag leaves in Yangdao 6, Wuyujing 3 were 35.6% and 34.7%, 26.9% and 35.3%, respectively. (4) Grain N content and grain yields were significantly reduced under treatments of cutting leaves. Grain N content was decreased by 6.9% in Yangdao 6 and 4.6% in Wuyujing 3 when removed mid-position leaves and decreased by 10.5% in Yangdao 6 and 9.2% in Wuyujing 3 when removed flag leaves. Grain yields were decreased by 7.3% in Yangdao 6 and 4.9% in Wuyujing 3 when removed mid-position leaves and decreased by 13.8% in Yangdao 6 and 11.1% in Wuyujing 3 when removed flag leaves. This suggested that flag leaves contributed largely to the accumulation of grain N and the production of yields. In general, net photosynthesis rate and N assimilation were significantly higher in cultivars with high N use efficiency than those in cultivars with low N use efficiency. On the other hand, N stored in mid-position leaves in cultivars with high N use efficiency can be transferred to the kernel to reutilize, thereby, N use efficiency was improved. This indicated there were different mechanisms in the N use efficiency between various rice cultivars.