Potassium(K)deficiency is one of the major abiotic stresses which has drastically influenced maize growth and yield around the world.However,the physiological mechanism of K deficiency tolerance is not yet fully understood.To identify the differences of root morphology,physiology and endogenous hormones at different growing stages,two maize inbred lines 90-21-3(tolerance to K deficiency)and D937(sensitive to K deficiency)were cultivated in the long-term K fertilizer experimental pool under high potassium(+K)and low potassium(-K)treatments.The results indicated that the root length,volume and surface area of 90-21-3 were significantly higher than those of D937 under-K treatment at different growing stages.It was noteworthy that the lateral roots of 90-21-3 were dramatically higher than those of D937 at tasselling and flowering stage under-K treatment.Meanwhile,the values of superoxide dismutase(SOD)and oxidizing force of 90-21-3were apparently higher than those of D937,whereas malondialdehyde(MDA)content of D937 was obviously increased.Compared with+K treatment,the indole-3-acetic acid(IAA)content of 90-21-3 was largely increased under-K treatment,whereas it was sharply decreased in D937.On the contrary,abscisic acid(ABA)content of 90-21-3 was slightly increased,but that of D937 was significantly increased.The zeatin riboside(ZR)content of 90-21-3 was significantly decreased,while that of D937 was relatively increased.These results indicated that the endogenous hormones were stimulated in 90-21-3to adjust lateral root development and to maintain the physiology function thereby alleviating K deficiency. Potassium (K) deficiency is one of the major abiotic stresses which has drastically influenced maize growth and yield around the world. Home, the physiological mechanism of K deficiency tolerance is not yet fully downloaded. To identify the differences of root morphology, physiology and endogenous hormones at different growing stages, two maize inbred lines 90-21-3 (tolerance to K deficiency) and D937 (sensitive to K deficiency) were cultivated in the long-term K fertilizer experimental pool under high potassium (+ K) and low potassium (-K) treatments.The results indicated that the root length, volume and surface area of ​​90-21-3 were significantly higher than those of D937 under-K treatment at different growing stages. It was noteworthy that the lateral roots of 90- 21-3 were dramatically higher than those of D937 at tasselling and flowering stage under-K treatment. Meanwhile, the values ​​of superoxide dismutase (SOD) and of an oxidizing force of 90-21-3were apparently higher than those of D937, whereas malondial Dehyde (MDA) content of D937 was significantly increased. Compared with + K treatment, the indole-3-acetic acid (IAA) content of 90-21-3 was largely increased under-K treatment, it was sharply decreased in D937. On the contrary, abscisic acid (ABA) content of 90-21-3 was slightly increased, but that of D937 was significantly increased. The zeatin riboside (ZR) content of 90-21-3 was significantly decreased, while that of D937 was more increased. These results indicated that the endogenous hormones were stimulated in 90-21-3 to adjust lateral root development and maintain the physiology function thereby alleviating K deficiency.