Influences of Mo on Nitrate Reductase, Glutamine Synthetase and Nitrogen Accumulation and Utilization in Mo-Efficient and Mo-Inefficient Winter Wheat Cultivars

The objective is to study whether the accumulation and utilization of plant N are controlled by Mo status in winter wheat cultivars. Mo-efficient cultivar 97003 （eft） and Mo-inefficient cultivar 97014 （ineff） were grown in severely Mo-deficient acidic soil （Tamm-reagent-extractable Mo 0.112 mg kg^-1） with （＋Mo） and without （-Mo） the application of 0.13 mg kg^-1 Mo. The accumulation and use efficiency of plant total N were significantly higher in ＋Mo than that in -Mo and in eft than that in ineff under Mo deficiency. N use efficiency was remarkably higher in maturity but it was forwarded to jointing stage after Mo supply, thus indicating that Mo supply promoted the N use efficiency besides N uptake and eff was efficient in N uptake and utilization. The overall activity of nitrate reductase （NR, EC 1.6.6.1） was significantly higher in ＋Mo than in -Mo and ratio of ＋Mo/-Mo was even to 14.8 at filleting stage for ineff. Activity of glutamine synthetase （GS, EC 6.3.1.2） was significantly lower in ＋Mo than in -Mo. Concentration of nitrate and glutamate were also significantly lower in ＋Mo than in -Mo, thus provided evidences for enhancing N use efficiency by Mo supply. Activities of NR and GS were significantly higher and concentrations of nitrate and glutamate were significantly lower in eff than ineff under Mo deficiency, thus indicated eff was more efficient in N reduction and utilization. It is therefore concluded that Mo could promote N accumulation and utilization in winter wheat which was directly related to NR and feedback regulated by GS. Higher Mo status also results in higher accumulation and utilization of plant N in eft.

植物液泡中硝酸盐行为的研究概况

化学氮肥利用率低和损失严重而造成的环境污染问题是农业生态系统中氮素管理首当其冲要研究和解决的问题 ,这方面的研究工作在国内外报道浩如烟海 ,但突破性进展不多。另一方面 ,植物体内的硝酸盐含量高又严重影响农产品有关的品质性状 ,特别是我国加入WTO后蔬菜和果实中高含量的硝酸盐是影响这些产品出口的主要限制因子之一。因此 ,从植物体本身着手研究植物氮素高效利用的机理与途径 ,这是近几年来植物氮素营养研究的热点之一。植物液泡占据了成熟植物细胞体积的 90 %左右 ,而液泡和细胞质中硝酸盐的浓度通常分别在 30～ 5 0molm- 3和 3～ 5molm- 3,因此 ,如何调动植物液泡中的硝酸盐使之得到更高程度的再利用 ,这是提高植物氮素利用效率和降低植物体内硝酸盐含量的途径之一。本文综述了国内外有关液泡中硝酸盐行为的研究状况 ,在此基础上作者首次提出植物液泡中硝酸盐的内外流与植物氮素高效利用之间可能存在着密切的关系 ,旨在拓始这方面的工作能尽快开展 ,为植物氮素高效利用的分子生物学研究开辟新的研究领域。