夏玉米各器官氮素积累与分配动态及其对氮肥的响应

为探明夏玉米各器官氮素积累与分配动态及其对氮肥的响应，以郑单958为材料，设置5个施氮水平进行了连续2年的大田定位研究。结果表明，除籽粒外各器官的氮素积累进程都呈单峰曲线，茎鞘在吐丝期达到峰值，而叶片、苞叶和穗轴则到吐丝后12 d左右达到峰值，之后逐渐下降；籽粒和整株的氮素积累随生育进程持续增加，成熟期最高。与其他器官相比，叶片对氮素供给更敏感，氮胁迫使叶片氮素积累高峰提前，促进氮素提前向外转运，导致其率先衰老。施氮能提高各器官在各生育时期的氮素积累量和积累速率，但不改变氮素积累变化趋势。总体上，施氮量180 kg N hm^-2可满足夏玉米对氮素的需求，获得较高的产量。以各器官氮素积累最大值与成熟期的差值计算，各处理再转运氮素对籽粒的贡献率均表现为叶片>茎鞘>穗轴>苞叶，各器官再转运氮素对籽粒贡献率之和平均为53.3%，其中苞叶和穗轴占12.3%，也是籽粒中氮素来源的重要组成部分。

Dynamic Responses of Nitrogen Accumulation and Remobilization in Summer Maize Organs to Nitrogen Fertilizer

A successive two years′ field experiment with five N application rates was conducted using hybrid Zhengdan 958. The results showed that the process of N accumulation in all organs except grain conformed to a unimodal curve in the whole life cycle. The N accumulation in blade, husk and cob reached the peak at around 12 days after silking, and that in stem and sheath at silking stage and then decreased gradually. The N accumulation in grain and the whole plant continuously increased, and the maximum value appeared at maturity. Compared with other organs, blade was more sensitive to N supply and N deficit stress made the N accumulation peak in advance, accelerated blade N remobilization and promoted senescence of blade. N supply significantly improved N accumulation amount and N accumulation rate in all organs at various stages, but did not change the trend of N accumulation. On the whole, the demands of maize organs for N could be met at theN application rate of 180 kg N ha^-1, and a higher grain yield also achieved. According to the maximum value of accumulated N in organs, the contribution of remobilized N from maize organs to grain showed a trend of: blade > stem and sheath > cob > bract, and the mean total contributionrate was 53.3%, of which cob and bract accounted for 12.3%, showing an essential part for grain N, too.