Abstract:The type and variation scenario of organic acid and amino acid in root exudates of different grain amaranth genotypes were studied under three levels of potassium supplication conditions at 3 development durations. The result shows: 1) The root exudation rates of amino acids and organic acids would decrease along with the rise of potassium supply level, meanwhile, amino acid and organic acids in root exudates of potassium-rich genotypes was always higher than that of common one. Under potassium stress condition, eleven kinds of amino acids and five kinds organic acids were found in root exudates, while glutamic, glycin, phenylalanine, oxalic acid and citric acid were missed under normal potassium supply conditon. Tyrosine, serine and γ-amidobutyricacid account for more than 50% of total exudates. While malic acid accouted for over 60% of total organic acid, which was the dominant one. 2) Compared with development stage at the fortith day, total exudation rates of amino acids and organic acids in common genotype at the fifith day decreased sharply, while it kept rather stationary in potassium-rich genotype; At three growth phrases, tyrosine, serine and γ-amidobutyricacid were dominant amino acids in root exudates of those two genotypes, malic acid was dominant organic acids, and the proportision of malic acid to total exudation increased with the prolongation of growth phase prolonged. 3) The content of available potassium treated with root exudates was markedly higher than control treanted by pure water treatment, and root excudates of potassium-rich genotype could activate potassiun in soil more than that of common genotype under potassium stress condition.