Abstract: The effects of the exogenous auxin——NAA, kinetin and wound on the callus formation of the cotyledon of mung bean (Phaseolus radiatus L.) with relation to the biosyntheses of endogeonous tryptophan (Trp) and IAA have been studied. The results indicate that wound plays an important role in the callus formation. The size of wounded surface is directly proportional to the proliferation of the callus tissue. The levels of free Trp and endogenous 1AA decreased in the initial period of the callus formation of mung bean cotyledon but increased in the later period. The substitution of L-Trp for NAA in the culture medium would play almost the same role in the callus proliferation. It has proposed that the exogenous phytohormones affect the biosyntheses of endogenous Trp and IAA, thereafter induce the callus formation. The wound has an important synergism with the phytohormones in this process.

Key words: Mung bean cotyledon, Formation of callus tissue, IAA, Tryptophan