Absorption of nutrients such as NO - 3, H 2PO - 4,K +,Ca 2+ ,SO 2- 4,Mg 2+ ,Zn 2+ ,and Cl - by plants. Such as barley, wheat, rice, corn and legumes was extensively investigated. It has been tested and proved by numerous experiments that kinetic parameters ( K m, I max , C min and E ) of given nutrient ions vary greatly among species and cultivars, and are influenced by plant age and nutrient supply. It follows that the parameters are of theoretical and practical importance in studying the adaptability of root system to its environment; in evaluating and screening absorption-efficient genotypes and in predicting nutrient absorption from soil by plant root system.