半干旱地区不同年代冬小麦品种根系生长和水分利用效率对种植密度的响应

优良的品种与科学合理的种植密度是提高小麦产量的基础。试验以3个不同年代在黄土高原半干旱地区大面积推广的冬小麦品种为试验材料，设置了3个种植密度（100万株/hm²、250万株/hm²、350万株/hm²），通过田间小区实验研究了种植密度对其根系生长，产量及其水分利用效率的影响。结果表明:不同年代冬小麦品种的根系生长，水分利用效率及其产量对种植密度的响应不同。1960s品种（丰产3号）的根系生长、产量及水分利用效率随种植密度的增加而降低；1980s品种（小偃6号）在中密度时根系生长，产量及水分利用效率最大，低密度次之，高密度最小；现代品种（长旱58）根系生长，产量及水分利用效率随种植密度的增加而提高。在本实验条件下，现代品种较前品种的最高水分利用效率和最高产量均显著增加，而相应的根重密度和根长密度却显著降低。这表明在黄土高原半干旱地区小麦品种更替过程中，小麦的根系生长可能存在对其产量和水分利用效率不利的冗余，只不过这种根系生长的冗余随品种的更替而降低，并因此提高了其水分利用效率和产量。

Responses of Root Growth and Water Use Efficiency to Planting Density for Winter Wheat Varieties from Different Eras in Semi-arid Region

Fine cultivar and suitable planting density are fundamentals for improving wheat yield. We tried to determine the influence of the planting density on the growth of root system, water use efficiency (WUE) and yields for winter wheat varieties from different eras in semi-arid region. Three cultivars introduced between 1960s and 2000s in the Loess Plateau were grown at three different planting density (100×10⁴ plants/hm², 250×10⁴ plants/hm² and 350×10⁴ plants/hm²) in the field. The results showed that the yields and WUE reduced along with the increase of planting density for the variety Fengchan3 in 1960s,; the yields and WUE were the highest at middle density for the variety-Xiaoyan6 in 1980s, followed by low density, and with the lowest at the maximum density; and the yields and WUE steadily increased along with the increase of planting density for the variety-Changhan58 in 2000s. We also found that the maximum yields and WUE of morden cultivar increased, but both root weight density and root length density reduced accordingly. Our findings suggest that there exists root redundancy, which is adverse for increasing yields and WUE in winter wheat in the Loess Plateau. However, this kind of redundancy reduced with varietal replacement and thus promotes the yields and WUE.