Growth Promoting Effect of Cyclitols on Spruce Tissue Cultures

Since the publication of Eastcott's work in 1928 (6). myo-inositol has been recognized as a growth factor for a number of micro-organisms. Although prol)ably of universal occurrence in plants and aninmals, its role in higher plants is still only partly understoo(l. Similarly, nmany of the isomers an(l derivatives of invo-inositol are commonly found in nature, vet until recently no function has been ascribed to any of these. The term, inositol, used without a prefix implies the nv1 o-isomler, also referred to as JCesoinositol in the older literature. The isomeric inositols and their (lerivatives all belong t) the larger group of conlpounds collectively known as cyclitols; this group recently has been reviewed Ibv Ang^,yal and Anderson (2). invo-Inositol frequently is added to culture media for plant tissues: there are only a few reports, however, of its actually being require(l by the tissues. Cultures derived fromn normal carrot tissue and Scorsonera crown gall (11) did not respond to mv1oinositol when thiamiin. biotin, an(l in(loleacetic acid were omitted from the medium; the inositol, however, greatly enhance(l the activity of the combined treatment with these compounds and also apparently decrease(l the toxicity of high levels of coconut milk. This effect is similar to that of synthetic bios in yeast cultures, in which the growth promoting activity of the vitamin niixtnre is often considerably greater than the combiilne(l effects of its ind(livi(lual constituents (14). Tiratun (4) stu(liecl the inositol requirements of tumior cells of tobacco with varying degreess of neoplastic change. Fully altered, rapidly-growving tumor cells did not respond to added inositol; slowto moderatelv-f~ast-g-roxving tumor cells were stimulated by an exogenotus supply of inositol although they w.vere capable of growth without it: normal cells also grew less on nle(lia lacking inositol.