The Growth and Metabolism of Excised Roots in Culture. I. the Measurement of Growth and the Role of Certain Vitamins.

It has long been recognized that one of the most essential needs of investigators of problems of growth and development in plants is experimental material in which growth and development can be studied in a rigidly controlled environment. Methods for the culture of parts of plants in *nutrient media under sterile conditions provide, in a measure, a means of controlling the environment. Successful isolated root culture experiments have been conducted by KOTTE (6, 7), ROBBINS (8), WHITE (16), ADDICOTT and BONNER (1) and BONNER and DEVIRIN (3) on more than 20 species of dicotyledonous plants. Much less success has characterized attempts to culture roots of monocotyledonous plants (WHALEY and LONG, 15). In general, the investigations have been concerned either with improvement of the techniques or with determining the general picture of physiological requirements of roots. BONNER and DEVIRIAN (3) and BONNER (4) have shown that roots of different species vary appreciably as to the nutrients with which they must be'supplied for satisfactory growth in culture. ROBBINS (13) and WHALEY and LONG (15) have shown that roots of different lines of tomato differ particularly in vitamin requirements. The results do not make it clear as to whether the differences in response to added vitamins represent differences in ability of the roots 'to synthesize these substances for themselves or differences in ability to utilize the supplements. It can be anticipated, however, that if such differences exist among lines within a given species they may play some part in the development of general metabolic differences. It should be possible to study the inheritance patterns of these differences by utilization of root culture techniques in combination with a hybridization program to produce progeny in which these same characteristics can be investigated. The present study has been aimed at detecting the existence of line differences in roots of the tomato, Lycopersicon esculentum Mill. and related species with respect to the ability of the roots to synthesize and/or utilize thiamin, pyridoxine and niacin; at evaluating the significance of such differences; and ultimately at studying the inheritance of these differences. 322