Cytokinins　(CTKs)　are　widely　used　in　agriculture　to　enhance　crop　production.　To　understand　the　role　of　CTKs　in　plant　growth　is　vital,　however,　molecular　mechanisms　underlying　CTKs　action　particularly　their　binding　kinetics　with　proteins　are　not　clear.　The　study　of　these　interactions　can　obtain　important　information　on　how　these　signal　molecules　regulate　cellular　processes　in　targeted　cells　locally　or　transport　to　other　functional　parts　of　plants.　In　this　study,　the　interactions　between　two　CTKs　and　soy　protein　were　investigated.　The　binding　constants　determined　at　30　degrees　C　were　KKT-soy　=　1.5　x　10(3)　M-1　and　KIP-soy=　0.67　x　10(2)　M-1　and　the　binding　stoichiometry　was　n(KT-soy)=　0.530　and　n(IP-soy)=　0.5165　respectively.　Moreover,　the　CTK-protein　interaction　is　found　to　be　a　static　quenching　process　via　an　energy　transfer　mechanism.　The　adduct　formed　through　electrostatic　interactions　under　the　plant　acidity　conditions　was　thus　transported　to　the　action　parts　of　the　plant　to　control　growth　process.