中文摘要：

为探明小麦品种更替过程中根系改良特征对氮肥的响应及其与产量形成的关系，从而为高产品种选育及根冠构型建成提供理论依据。本研究以长江中下游不同年代大面积推广的代表性小麦品种南大2419、扬麦1号、扬麦158和扬麦16为材料，采用大田和盆栽试验，研究了3个施氮水平（纯氮0、225和300kghm^-2）下小麦根系形态与生理特性的差异及其与产量的关系。结果表明，小麦籽粒产量随品种育成年代推进逐步增加，现代品种对施氮的响应较早期品种大。现代小麦品种拔节至开花阶段根系干物质积累量和生长速率显著高于早期品种，而播种至拔节期早期品种的根系生长在无氮条件下具有较强的生长优势。小麦根系总根长、表面积、根体积、0～60cm土层根重密度、根系活力和SOD活性随品种育成年代逐步提高，而MDA含量显著降低。增施氮肥促进了不同年代品种根系生长，但现代品种增幅较早期品种大，说明品种改良提高了小麦根系对氮肥的响应。籽粒产量与开花期根系总根长、表面积、根系生物量和O～60cm根重密度呈显著正相关。因此，增加根系与土壤接触面积和高氮适应性、提高根系生理活性、延缓根系衰老是长江中下游小麦品种演变的重要特征也是高产高效栽培调控的重要目标。

英文摘要：

Exploring the characteristics of root growth, root physiology and their relationships to grain yield in wheat cultivars released in different decades will facilitate the development of new wheat cultivars, with stable and high yields and low nitrogen fertilizer input. Four wheat cultivars Nanda 2419, Yangmai 1, Yangmai 158, and Yangmai 16, which were bred or widely planted in the Middle-Lower Yangtze River Basin after 1950, were used in field and pot experiments in 2010-2011 with three nitrogen rates （pure N 0, 225, and 300 kg ha-l）. The results showed that, grain yield was improved with the genetic improvement in wheat breeding and the sensitivity of modem cultivars to N was greater as compared with early released cultivars. The root dry matter accumulation （DMA） and growth rate from jointing to anthesis of modem cultivars were higher than these of early released culti- vars. The root length, root surface area, root volume and density of root weight in 0-60 cm soil layer were enhanced with the ge- netic improvement in wheat breeding, while no change was found in proportion of root distribution. The root activity, MDA con- centration and SOD activity in modem cultivars were improved significantly. Higher N application increased root growth and physiological performance, with larger effects in modem cultivars, indicating that the response to N and high-N tolerance were promoted with genetic improvement in wheat breeding. In addition, these were significantly positive relations of grain yield with total root length, root surface area, root biomass and density of root weight in 0qS0 cm soil layer. Therefore, higher contact area of the roots with soil and high-N adaptability, enhanced root physiological activity and N assimilation capacity, and delayed senes- cence of root system should be the important characteristics in cultivar evolution in the Middle-Lower Yangtze River, which are the main purpose getting in high-yield and high efficiency cultivation in this region.