中文摘要：

利用微管对狗尾草（Setaria viridis）、黄蒿（Artemisia scoparia）和沙米（Agriophyllum squarrosum）根系生长动态进行了观测。结果表明：1）在观察期内,狗尾草和黄蒿的根系生长表现出先增后减的“抛物线”型,而沙米的根系成指数生长。在7月末至8月初狗尾草、黄蒿和沙米根系具有最高的生产量,其根量密度分别为4690.91、2975.76和2354.55条·m^-2;在8月末,狗尾草和黄蒿根系都表现出不同程度的衰减,沙米根数保持增加。2）狗尾草优先生长表层根系,根系主要生长在0～30cm的土层内,根长密度最大时为2.23cm·cm^-2;黄蒿生长前期表层根长密度大,生长后期下层根长密度开始增加;沙米优先发展下层根系,快速生长期后,地下30～50cm处的根长密度增加高于上层。3）生长前期和快速生长期,0～50cm狗尾草根长密度最大,黄蒿次之,沙米最小,生长末期,沙米根长密度大于狗尾草。

英文摘要：

Aims We selected three representative grasses in Horqin Sandy Land and measured their root dynamic by minirhizotrons,a nondestructive,in situ method for directly viewing and studying root dynamics.Methods The experiment was conducted on three quarters（2 m×2 m）of Naiman Desertification Research Station,Chinese Academy of Sciences during the 2005 growing season.The sandy soil was transported from a sandy dune and sifted through a 0.5 mm sieve.On May 15,seeds of Setaria viridis,Artemisia scoparia and Agriophyllum squarrosum were cultivated in each quarter,respectively.Three minirhizotrons（50 cm long and 7 cm outer diameter）per treatment were installed at right angles.A black cover blocked light from entering the section of the transparent tube left above ground.For each treatment,three tubes were installed in the center parallel to the plant row,10 cm from the row.Each quarter was supplied with enough water until June 5,and thereafter precipitation was the only water source.According to plant needs,seedlings of three grasses were kept 15 cm apart in rows and 20 cm apart between rows.The number of roots on the minirhizotron wall was obtained using a mirror,and root length was estimated counting the number of intersections of roots with a 1 cm-mesh grid,using the modified Newman-Line-Intersect method.Important findings The curves of total root number of S.viridis and Artemisia scoparia after seed germination fitted a cubic regression model,while that of Agriophyllum squarrosum showed exponential increase.The production of S.viridis and Artemisia scoparia peaked by the end of July or the beginning of August and then decreased,while Agriophyllum squarrosum showed an opposite trend.Roots of S.viridis were concentrated within the top 30 cm of the soil profile where the maximum root length intensity achieved 2.23 cm·cm^-2.Vertical root distribution of S.scoparia had an almost symmetrical pattern.At the prophase of growth period,it preferentially developed superficial roots,while at the end of the growth period,ro