Lee, A. L.
Clones of excised tomato roots have been established from seed of the wd mutant as well as from seed with its normal allele wd+; likewise from seed of the d^x mutant and from seed with its normal allele (d^+). Seed for all of these cultures were kindly provided by Dr. C. M. Rick.
Seeds were sterilized and allowed to germinate under aseptic conditions, after which root cultures were grown following standard procedures (White, 1943, a handbook of plant tissue culture. Cattell Press.). At each planting, 80% or more of all the seed germinated.
All attempts to establish clones of wd^+ roots from the seed which had germinated were successful, while only 50-69% of the wd roots were successful. About one-half of these showed reduced growth in culture. Growth in length of normal roots (wd^+) and number of laterals produced exceeded that of the dwarf roots (wd) by 25-35% for a given period of time. Daily measurements indicated that it was the rate of growth which differed between the two types. wd^+ roots had about 25% more fresh weight when compared to wd roots after a 7-day growth period while dry weight was about the same during this period. Total nitrogen as percent of dry weight was higher for wd roots than for wd^+ roots. Measurements of cell lengths at given locations along the main axis gave similar data for both wd and wd^+ roots.
Growth of the roots in media supplemented with various growth substances was determined. Kinetin stimulated growth of both wd and wd^+ roots, while gibberellic acid inhibited growth of both types. wd roots were much less sensitive to gibberellic acid than wd^+ roots.
All attempts to establish clones of both d^x roots and d^+ roots from seed which had germinated were successful. These were studied later and less extensively than the wd series. Growth in length and number of laterals produced by the d^x roots was 40-50% of that of d^+ roots for a given period of time. d^+ and d^x roots responded to gibberellic acid supplied in the culture medium in a manner very similar to that of wd and wd^+ roots.
Details of all these investigations will be published elsewhere.