Thiamine requirements of various plant cells in suspension culture

The thiamine requirements of cells of several plant speciesin suspension culture were investigated. Omission of thiaminefrom the medium leads to a rapid and complete cessation of growthin subcultures of soybean, tobacco and rice cells. The criticallevels of thiamine content in these cells are considered tobe in the vicinity of 0.6, 0.5 and 0.2 µg per g dry weight,respectively. Soybean cells can grow satisfactorily when suppliedwith an equimolar mixture of two thiamine precursors, pyrimidineand thiazole moieties. Neither moiety alone can substitute forthiamine. On the other hand, Rula and peanut cells can be successfullysubcultured for ten passages in the absence of externally suppliedthiamine. When grown without thiamine, Rula cells had an averagethiamine content of 0.5-0.6 µg in darkness and 3.5 µgper g dry weight in the light. The relationship between thethiamine requirement and the degree of dedifferentiation incultured cells is discussed. ¹ Present address: Section of Phytochemical Research, Researchand Development Division, Eisai Co., Ltd., Kawashima, Gifu 112,Japan. (Received December 24, 1975; )