TGC REPORT No . 31, 1981 RESEARCH NOTES 12 mutation, this medium stimulated growth of the mutant . The significance of this observation may be that the pds/pds mutants are not defective in phosphorus metabolism . pds may be a lesion in the metabolism of nitrate which mimics the phosphate deficiency syndrome . Table 1 . The effect of Pi concentration on the growth of VF - 36 and pds/pds callus . The callus was initiated and grown as described in the methods section . The initial inoculum was 4 pieces of callus per plate, each weighing approximately 400 mg . The callus was allowed to grow for 30 d in the light . Table 2 . The effect of P - choline on callus induction and growth . The VF - 36, pds/pds and L . pimpinellifolium seeds were germinated and the seedlings were grown on MS medium . The hypocotyls were excised after 10 d of growth and four 1 cm segments, each obtained from 1 seedling, were placed on the various media . The callus was weighed after 30 d .