Amino Acids as Complementary Factors for the Growth and Redifferentiation of Rice Callus Tissues

Abstract

Effects of several substances on the callus growth induced by gibberellic acid (GA₃) were studied with yeast extract (YE), casein hydrolysate (CH), kinetin, single amino acids and the mixture of amino acids in rice varieties, Tan ginbozu, Waisei shinriki, Aichi asahi and Te-Tep using Maeda's medium. An effect of CH on the kinetin activities to organ formation was also investigated in callus tissue, var. Aichi asahi. (1) A chemically defined medium did not reveal the GA₃ response, that is a remarkable growth promoting phenomenon in callus tissues by the interaction of 2, 4-dichrolophenoxyacetic acid (2, 4-D) and GA₃ in the YE containing medium. Also, the effect of kinetin on the shoot formation in Aichi asahi callus tissue disappeared in the chemically defined medium. (2) In the chemically defined medium, the GA₃ response on the growth of Tan ginbozu callus tissue was neither appeared by increasing of GA₃ concentrations, nor by application of kinetin. Any GA₃ response was not appeared by application of single amino acids, i. e. L-arginine, proline, glycine and DL-methionine. Both of L-lysine and L-threonine indicated slightly the GA₃ response. (3) When YE and CH were added in the chemically defind medium, the GA₃ response was induced in Tan ginbozu callus tissues. Moreover, when the mixture of amino acids prepared as same proportion as Bacto-Yeast Extract was added, the response appeared conspicuously. In Aichi asahi callus tissue cultured in CH medium, kinetin had a promoting effect on shoot formation but GA₃ revealed an inhibitive effect strikingly. Above mentioned results indicate that a mixture of many amino acids is required for the GA₃ response on the growth or the activities of kinetin on organ formation as a complementary factor in rice callus tissues. Therefore it is assumed that the callus growth and shoot formation are closely connected with the amino acid metabolism in the callus tissues.