光强和氮肥互作对南方软米粳稻灌浆结实期碳氮代谢影响及其与产量品质间关系

Effects of light intensity and nitrogen fertilizer interaction on carbon and nitrogen metabolism at grain-filling stage and its relationship with yield and quality of southern soft japonica rice

以南方软米粳稻南粳9108和扬农香28为材料,设置2个光强处理和4种氮肥处理,其中光强处理于结实期展开,分为100%自然光照强度(L1)和50%自然光照强度(L2),氮肥处理为生长中后期不施氮肥(N1),分别于倒六叶(N2)、倒四叶(N3)、倒二叶(N4)期一次性施用氮肥,研究了不同光照强度、氮肥施用时期及光氮互作条件下水稻结实期碳氮代谢差异及其对产量和品质的影响。结果表明,结实期光强减弱,剑叶净光合速率下降7.35%-42.36%、叶片中蔗糖磷酸合酶(SPS)和蔗糖合酶(SS)酶活性下降,叶片C/N比下降3.98-6.49,光合产物向籽粒输送减少,籽粒中淀粉(包括直链淀粉)含量降低,同时叶片中硝酸还原酶(NR)、谷氨酰胺合酶(GS)、谷氨酸合酶(GOGAT)活性增强,植株含氮率提升,蛋白质含量相对增加,不利于产量和优良品质的形成。中后期施用氮肥后,叶片中碳氮代谢关键酶活性显著提高、叶片的衰老减缓,水稻的灌浆结实期延长,有利于产量的提升。随中后期氮肥施用时期推迟,氮代谢愈发旺盛,籽粒中蛋白质含量相对明显增加,导致淀粉与蛋白质、直链淀粉与蛋白质的比值均下降,食味值下降。本试验条件下,正常光照配合倒四叶施用氮肥处理(L1-N3)能够协同提高叶片碳氮代谢关键酶活性,使得光合产物和含氮化合物以适宜的比例向籽粒输送,最终籽粒中淀粉与蛋白质的比值在11.43-12.03之间,直链淀粉与蛋白质的比值在1.34-1.50之间,米饭的硬度低,黏度、平衡性高,食味好,可同时获得高产和优质。

Southern soft japonica rice Nanjing 9108 and Yangnongxiang 28 were selected as the experimental materials,and two light intensity treatments,and four nitrogen treatments were set.Light intensity treatments[100%natural light intensity(L1)and 50%natural light intensity(L2)]and four nitrogen treatments[no nitrogen fertilizer(N1)in the middle and late growth stages,one-time nitrogen fertilizer applied at the top sixth leaf stage(N2),one-time nitrogen fertilizer applied at the top fourth leaf stage(N3),and one-time nitrogen fertilizer applied at the top second leaf stage(N4)]were conducted at grain-filling stage.The difference of carbon and nitrogen metabolism at grain-filling stage and its effects on rice yield and quality under the conditions of different light intensity and nitrogen application period as well as light-nitrogen interaction conditions were investigated.The results showed that with the decrease of light intensity at grain-filling stage the net photosynthetic rate of flag leaf decreased by 7.35%-42.36%on average,sucrose phosphate synthase(SPS),and sucrose synthase(SS)had low activity,the C/N ratio of leaves decreased by 3.98-6.49,the transportation of photosynthetic products to grains decreased,and the content of grain starch(including amylose)decreased.Meanwhile,the activities of nitrate reductase(NR),glutamine synthetase(GS),and glutamate synthetase(GOGAT)increased,plant nitrogen concentration increased,and the accumulation of protein increased relatively,which were not conducive to the formation of yield and good quality.After the application of nitrogen fertilizer at the middle and late growth stages,the activities of key enzyme in carbon and nitrogen metabolism in leaves were significantly increased,the aging of leaves was slowed down,and the grain-filling period of rice was prolonged,which were conducive to the increase of yield.With the delay of nitrogen fertilizer application period,nitrogen metabolism became more vigorous,and the protein content in grain had a relative significant increase,resulting in the decrease of the ratio of starch to protein and the ratio of amylose to protein,and the decrease of taste value.Under the experimental condition,normal light intensity combined with nitrogen fertilizer treatment(L1-N3)at the top fourth leaf stage synergistically improved the activities of key enzymes of carbon and nitrogen metabolism in leaves,thus the photosynthetic products and nitrogen-containing compounds were transported to grains in the appropriate proportions.Ultimately,the ratio of starch to protein in grain ranged from 11.43 to 12.03,and the ratio of amylose to protein ranged from 1.34 to 1.50,the rice had low hardness,high viscosity,and balance as well as good taste,high yield,and excellent quality could be obtained simultaneously.