4.4. Suppression of floral organs
It has shown that the morphology of the floral organs regulated by mechanical pressures, meristem geometry, its changes during development and gene programs (e.g. Green, 1992, 1999; Caris et al. 2002, Iwamoto and Bull-Hereñu 2018, Iwamoto et al. 2015, Claßen-Bockhoff and Meyer 2016, Claßen-Bockhoff et al. 2021). The experimental studies confirmed that in absence of such mechanical pressures, the actual shape of the flower would not appear (Bull-Hereñu et al. 2022).
The calyx covers the petals during the developmental process and protects them. In Apiaceae, the involucral bracts and involucellar bracteols replace it, instead. The calyx teeth, therefore, reduced as small points or rarely absent. The absolute suppression of calyx teeth in C. bulbosum and P. sativa related to space limitation throughout development (Ajani et al. 2016). In Hydrocotyle vulgare (formerly in Apiaceae), in contrast, it is genetically fixed, thereby, it resembled to Araliaceae (Erbar and Leins 1985, Leins and Erbar 2004). In perfect flowers of Di. persica , such mechanical pressures along with space limitations persist specially at the early stages of umbellet fractionation. Such forces and its effects on floral geometry imposed by massive inner staminate floral meristems at the early stages that inhibited the fractionation of the perfect flower. By elongation of the pedicels, it reduced, that, in turn, effects on flexibility of the perfect floral primordium, providing spaces only for expansion and fast fractionation of its flower organs.
The peripheral staminate ray flowers are explaining the absence or presence of such forces. On abaxial side, two sepals are well developed and hardened due to absence of such constrains. The occurrence of such forces at the adaxial side, in contrast, get inhibited the sepals from inception. These data are in agreement with previous findings in Apiaceae with pseudanthia inflorescences such as Echinophora trichophylla (Baczyński et al. 2022).