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根系在氮素高效吸收过程中起重要作用,但人们对玉米育种过程中不同年代杂交种的根系生长特性及其对氮素供应的响应了解较少.选用中国1973～2009年育成的11个代表性玉米品种,在水培体系下研究了正常供氮(4mmol/L)和低氮(0.04mmol/L)下根系与地上部生长差异.结果表明,与低氮处理相比,正常供氮降低根干重、根冠比和根系相对生长速率,但增加总根长和侧根长.对于20世纪90年代之前育成品种,供氮还降低总轴根长.氮处理不影响种子根数.随育种年代演进,地上部相对生长速率表现明显增加,不同氮水平下表现一致.但是,根系相对生长速率仅在正常供氮条件下表现出与育成年代线性相关.相应地,只在正常供氮条件下玉米总根长、侧根长、轴根长表现为随育成年代增加而明显增加.因此,在过去36年的玉米育种进程中,玉米地上部生长势在不同氮供应水平下均得到提高,而根系生长则只在正常供氮条件下得到提高.进一步改良根系在低氮环境下的生长能力可能提高现代玉米品种的氮吸收效率.
The root system plays an important role in the process of high nitrogen uptake, but little is known about the root growth characteristics and the response to nitrogen supply in hybrids of different age in corn breeding process.On the basis of eleven representatives bred from 1973 to 2009 in China, Sex maize cultivars, the differences of root and shoot growth under normal nitrogen supply (4 mmol / L) and low nitrogen (0.04 mmol / L) were studied under hydroponic system.The results showed that compared with low nitrogen treatment, the normal nitrogen supply decreased Root dry weight, root / shoot ratio and root relative growth rate, but increased the total root length and lateral root length.For the cultivated varieties prior to the 1990s, the total nitrogen supply also reduced the total root length.The nitrogen treatment did not affect the seed number. However, the relative growth rate of roots showed a linear correlation with the age of fertility only under normal nitrogen supply.Accordingly, under the condition of normal nitrogen supply only, the relative growth rate of aboveground part increased obviously, The total root length, lateral root length and axial root length of maize increased significantly with the increase of breeding age. Therefore, in the process of maize breeding in the past 36 years, the growth of corn shoots increased under different levels of nitrogen supply, The growth of root system was only improved under the condition of normal nitrogen supply.Improving the growth ability of root system in low nitrogen environment may improve the nitrogen absorption efficiency of modern maize varieties.