4.4. Floral bud differentiation characteristics
According to Fig. 2, the floral bud differentiation of E. grandiflorum TDC was a centripetal and consecutive process, which included
5 distinct stages (except the vegetative growth phase in Table 2):
initial differentiation phase, sepal primordia differentiation phase,
petal primordia differentiation phase, stamen primordia differentiation phase and pistil primordia differentiation phase. For different
research purposes, scientists used different standards in dividing
flower bud differentiation process of lisianthus. For instance, Zaccai
and Edri (2002) revealed three distinct stages of floral bud development in ‘Heidi Deep Blue’, while Islam et al. (2005) divided flower
bud differentiation into 7 stages for ‘Fuji Deep Blue’. Moreover, the
cultivar-dependent inconsistency in lisianthus floral bud differentiation also existed between the single-flowered ‘Fuji Deep Blue’ and the double-flowered ‘Echo Blue’. For ‘Echo Blue’, it was difficult
to distinguish between the second and/or third layer of petals and
the stamen initiation because the petals and stamens developed
simultaneously (Islam et al., 2005). These results also suggested
that differences existed in the floral differentiation process among
various cultivars