Key Laboratory of Plant-Soil Interaction, MOE, College of Resources and Environmental Science, China Agricultural University, Beijing, 100193, China.
Sci China Life Sci. 2011 Jul;54(7):642-50. doi: 10.1007/s11427-011-4186-6. Epub 2011 Jul 12.
Root growth has a fundamental role in nitrogen (N) use efficiency. Nevertheless, little is known about how modern breeding progress has affected root growth and its responses to N supply. The root and shoot growth of a core set of 11 representative Chinese maize (Zea mays L.) hybrids released between 1973 and 2009 were investigated under high N (4 mmol L(-1), HN) and low N (0.04 mmol L(-1), LN) levels in a solution culture system. Compared with LN, HN treatment decreased root dry weight (RDW), the root: shoot ratio (R/S), and the relative growth rate for root dry weight (RGR(root)), but increased the total root length (TRL) and the total lateral root length (LRL). The total axial root length (ARL) per plant was reduced under HN, mostly in hybrids released before the 1990s. The number of seminal roots (SRN) was largely unaffected by different N levels. More recently released hybrids showed higher relative growth rates in the shoot under both HN and LN. However, the roots only showed increased RGR under HN treatment. Correspondingly, there was a positive linear relationship with the year of hybrid release for TRL, LRL and ARL under HN treatment. Together, these results suggest that while shoot growth of maize has improved, its root growth has only improved under high N conditions over the last 36 years of selective breeding in China. Improving root growth under LN conditions may be necessary to increase the N use efficiency of maize.
根生长在氮（N）利用效率中起着重要作用。然而，人们对现代育种进展如何影响根生长及其对 N 供应的反应知之甚少。在溶液培养系统中，用高氮（4 mmol L(-1)，HN）和低氮（0.04 mmol L(-1)，LN）处理，研究了 1973 年至 2009 年间发布的 11 个有代表性的中国玉米（Zea mays L.）杂交种核心系的根和地上部生长。与 LN 相比，HN 处理降低了根干重（RDW）、根冠比（R/S）和根干重的相对生长率（RGR(root)），但增加了总根长（TRL）和总侧根长（LRL）。HN 下植物的总轴向根长（ARL）减少，主要在 20 世纪 90 年代之前发布的杂交种中。不同氮水平对 seminal 根（SRN）数量影响不大。最近发布的杂交种在 HN 和 LN 下的地上部具有更高的相对生长率。然而，只有在 HN 处理下，根才显示出更高的 RGR。相应地，在 HN 处理下，TRL、LRL 和 ARL 与杂交种发布年份之间存在正线性关系。总之，这些结果表明，在中国过去 36 年的选择性育种中，虽然玉米地上部生长得到了改善，但根生长仅在高氮条件下得到了改善。在 LN 条件下提高根生长可能是提高玉米氮利用效率的必要条件。
