The constituents of the roots bleeding sap are an important index characteristic of roots activity and roots-shoots relationship. To compare the differences between the constituents of roots bleeding sap from maize and soybean plants, roots bleeding saps were collected from maize (Zea mays L. cultivar 3138) and soybean [Glycine max (L.) Merr. cultivar Ludou 11] plants at different growth and development stages under field condition, and the inorganic elements were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results indicated that both the constituents of inorganic elements and flow intensities were various between roots bleeding saps from maize and soybean plants at different growth and development stages. The flux of inorganic elements in roots bleeding sap showed different trends with progress in plants growth and development. In the roots bleeding sap from maize, the predominant inorganic elements were K, Ca, Mg, P, Na, Si, Zn, Mn and Fe, with flux ranging from 1 to 1 851.5 microg x h(-1) x plant(-1). The flux of B, Cu and Mo was relatively lower and less than 1 microg x h(-1) x plant(-1), while none of the elements of Co, Cd, Ba, Pb, Sr and As could be detected, and was estimated to be lower than 0.01 microg x h(-1) x plant(-1) based on the detection limit. The flow of most inorganic elements showed decreasing trends with plant development progressing from booting to grain filling stage. In the roots bleeding sap from soybean, Ca, Mg, K, P, Na, Zn, Mn, Fe and Cu were found as predominant inorganic constituents, ranging from 1 to 1 158 microg x h(-1) x plant(-1). The flow of both B and Mo was found lower than 1 microg x h(-1) x plant(-1), and none of Si, Co, Cd, Ba, Pb, Sr and As could be found. With the growth and development, different inorganic elements showed various changing pattern.