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).