Abstract: Soluble sugar has positive influence on plant frost resistance. In order to study the effects of alfalfa and grass mixed sowing on soluble sugar content of their root system,  the legume-grass system, including alfalfa and 3 kinds of forage grasses (Bromus inermis Leyss, Elymus dahuricus Turcz and Phalaris arundinacea L.), were sowed at every other line proportion of 1∶1 (B1), 2∶2 (B2), 1∶2 (B3) and 2∶1 (B4). Then after the first frost, the soluble sugar contents in different mixed seeding grass root system were measured. Results showed that the contents of soluble sugars in alfalfa root  were not significantly affected by grass varieties, and the soluble sugar content of alfalfa root in the proportion of 2∶2 between legume and grass was significantly lower than that of 1∶2, 2∶1. There was no significant difference between proportions of 1∶1, 1∶2 and 2∶1. By mixing alfalfa with P. arundinacea, the soluble sugar content in  root  of P. arundinacea was higher than that in single planting of P. arundinacea. Among the 3 grasses, the soluble sugar content in P. arundinacea root  was significantly higher than those of the other two. To sum up, the soluble sugar contents in alfalfa and grass roots  were both higher than those of mixed sowing at proportion of 1∶1 and 1∶2. Considering the cold tolerance of alfalfa was usually weaker than those of the 3 grasses, the optimal choice would be the treatment with every other line proportion of 1∶2. The present reseach provided  theoretical reference for sustainable utilization of local legume-grass mixed grassland.

Key words: alfalfa, grass, mixed sowing, root system, soluble sugar

摘要： 可溶性糖对植物的抗冻性存在着积极的影响。为研究苜蓿（Medicago sativa）与禾草混播对根系可溶性糖含量的影响，以苜蓿与无芒雀麦（Bromus inermis Leyss）、披碱草（Elymus dahuricus Turcz）、虉草（Phalaris arundinacea L.）按豆禾间行比例1∶1(B1)、2∶2(B2)、1∶2(B3)和2∶1(B4)混播，并在初霜后测定不同混播处理牧草根系的可溶性糖含量。结果表明，禾草种类对苜蓿根系可溶性糖含量的影响不显著；豆禾间行比例2∶2混播处理苜蓿根系可溶性糖含量显著低于1∶2和2∶1混播处理，1∶1、1∶2和2∶1混播处理间无显著差异；苜蓿与虉草混播后，不同混播比例的虉草根系可溶性糖含量都高于单播虉草。3种禾草中，虉草根系可溶性糖含量显著高于其余两种。综上所述，豆禾间行比为1∶1及1∶2混播处理中苜蓿及禾草的根系可溶性糖含量均较高，考虑苜蓿的耐寒力往往弱于3种禾草，又以间行比1∶2混播的处理为最佳选择。研究为当地苜蓿与禾草混播草地的持续利用提供理论参考。

关键词: 苜蓿, 禾草, 混播, 根系, 可溶性糖