Effects of Thiamin, Niacin, and Pyridoxine on Interval Growth of Excised Tomato Roots in Culture

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Abstract
The growth of excised roots of a line of tomato derived originally from a cross between Lycopersicym esculentum and L. pimpinellifolium. but selfed through 8 generations before this expt. was detd. at weekly intervals for 4 weeks when roots were grown in White''s medium without vitamin supplements or in this medium with individual or combined supplements of thiamin, niacin, and pyridoxine. Growth in all media was similar during the first wk. Little additional growth was obtained from roots grown in unsupplemented medium or in media containing pyridoxine or niacin alone. In media containing thiamin alone, or combinations of any 2 or 3 of the vitamins, growth of roots was significantly greater than in the other media. In medium containing all 3 vitamins, growth was significantly greater than in any other medium. Between the 3d and 4th wks., however, growth in all cultures, including those fully supplemented, was markedly reduced. Hence, the best period for investigation of growth-substance effects under these exptl. conditions was during the 2d and 3d weeks. The data emphasize the importance of the interrelationships and balances which must exist among these vitamins in root metabolism.