The epidermal
cells of calyx show enlargement and lobation post-fertilization. Application of hormones to depistillated
flower buds of Withania revealed that cytokinins and gibberellins mimic fertilization signals. The ICS
development is a synchronous step with fruit development; both processes are under the control of more
or less the same set of hormones, including cytokinins and gibberellic acids. Interestingly, inhibition of
ethylene in the system is sufficient to yield inflated calyx in Withania. In contrast, Tubocapsicum, a closely
related species and an evolutionary natural loss mutant of ICS – showed no response to applied hormones,
and ethylene led to inflation of the receptacle indirectly. In addition to hormones, the expression of
an MPF2-like MADS-box transcription factor in sepals is essential for ICS formation. Nevertheless, the
interactions between MPF2-like genes and hormones are barely detectable at the transcript level. Our data
provide insight into the role of hormones in generating floral morphological diversity during evolution.