Digby J, Skoog F
Department of Botany, University of Wisconsin, Madison, Wisconsin.
Plant Physiol. 1966 Apr;41(4):647-52. doi: 10.1104/pp.41.4.647.
Bioassays of tissue extracts show that high (500-1000 mug/liter) kinetin concentrations which permit growth of tobacco callus cultures on media without added thiamine activate the biosynthesis of this vitamin by the tissues. Although the tissue concentration of thiamine may fall appreciably, it is maintained at a level adequate for survival and slow growth of the cultures, and there is a large net increase in total thiamine content per culture with time. In the second and subsequent passages of tissue on a thiamine free medium, growth is obtained only when high kinetin concentrations are maintained. Effective inhibition of growth by antithiamines suggests that thiamine is utilized by the high-kinetin tissue.In the presence of low (30-100 mug/liter) kinetin concentrations, which would be optimal for growth in the presence of thiamine, growth only occurs early in the first passage of tissue from a medium with the vitamin to one without it. The thiamine concentration in the tissues falls to low levels, and no net biosynthesis is apparent. The tissues turn dark and die after 2 to 3 weeks. In contrast with this, in the absence of both added thiamine and kinetin no appreciable growth occurs, but the tissues keep their normal appearance, retain their thiamine content, and may stay alive for several weeks.
组织提取物的生物测定表明，高浓度（500 - 1000微克/升）的激动素能使烟草愈伤组织培养物在不添加硫胺素的培养基上生长，它还能激活组织中这种维生素的生物合成。虽然硫胺素的组织浓度可能会显著下降，但仍能维持在足以使培养物存活和缓慢生长的水平，并且随着时间的推移，每个培养物中硫胺素的总含量会有大量净增加。在无硫胺素培养基上进行组织继代培养时，只有保持高浓度的激动素才能获得生长。抗硫胺素对生长的有效抑制表明硫胺素被高浓度激动素处理的组织所利用。在低浓度（30 - 100微克/升）激动素存在的情况下，这一浓度在有硫胺素时对生长是最佳的，但只有在组织从含维生素的培养基转移到不含维生素的培养基的首次传代早期才会生长。组织中的硫胺素浓度会降至低水平，且没有明显的净生物合成。2至3周后，组织会变黑并死亡。与此相反，在既不添加硫胺素也不添加激动素的情况下，组织没有明显生长，但能保持正常外观，保留硫胺素含量，并可能存活数周。
