| Flowers of a previously undescribed recessive mutant of tomato (Lycopersicon esculentum), green pistillate (gpi), show strong and consistent homeotic transformation of petals to sepals and stamens to carpels. Wild type and mutant do not differ in the pattern of stamen initiation, as shown by allometric analysis of scanning electron micrographs, and by kinematic analysis of cell behavior in individual stamen primordia using a nondestructive replica method for electron microscopy. Allometry shows that sepaloid petals and carpelloid stamens of the mutant elongate at relative rates normal for organs of the occupied whorls. Thus floral organ placement, and some aspects of organ growth such as elongation rate, seem independent of mechanisms controlling organ identity.;Double mutants were constructed bearing both green pistillate and lateral suppressor (ls), which confers absence of petals. Deviations from a simply additive ls-gpi phenotype included an increase in the number of second whorl organs (sepaloid petals typical of gpi), and sepaloid or stamenoid features on roughly 25% of third whorl organs. The gpi phenotype in F2 hybrids of L. esculentum and Lycopersicon pennellii a wild relative of tomato, showed no difference in the second whorl but a wide range in the third whorl. The frequency of the most common phenotypic class, with nearly wild type stamen morphology, indicates that three dominant modifier genes from L. pennellii are responsible for the phenotypic range.;To test the importance of cellulose deposition in the patterning of floral organ primordia, early floral meristems of Anagallis arvensis were locally treated with the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile (DCB). Two major classes of defect occurred in flowers showing no signs of cell death or wounding: local stunting or ablation of organs in the area of treatment (41%), and overall changes in the symmetry number of the flower from the normal five-fold to four- and three-fold (5%). Flowers with shifted symmetry initiated sepals at an abnormally small meristem diameter, but diameter did not correlate perfectly with organ number. Kinematic analysis showed normal stamen and precarpel growth behavior in the shifted flowers, including cells originally in contact with DCB. |
