PHENOTYPIC CHARACTERIZATION AND MOLECULAR MAPPING OF AN ACAULIS2 MUTANT OF ARABIDOPSIS-THALIANA WITH FLOWER STALKS OF MUCH REDUCED LENGTH

An acaulis2-1 (acl2-1) mutant of Arabidopsis thaliana (L.) Heynh. was isolated and characterized. The mutant had inflorescences of much reduced length. The defect was severer in lower internodes and was visible preferentially in type 2 metamers. The defect in the elongation of internodal cells of inflorescences was attributable to a defect in the mechanism for elongation of these cells. The cortical microtubules (MTs) were analyzed in the acl2 mutant, in a comparison with those of an acl1 mutant which was described earlier, but no changes were detected in amounts of MTs. In the type 2 and type 3 metamers, the defect in elongation in acl mutants was loosely correlated with a change in the orientation of MTs. Thus, the abnormal arrangement of MTs appears to be one of the pleiotropic effects of acaulis mutations. Genetic mapping was performed using molecular markers and the ACL2 gene was located at 100 map units on chromosome 1.