4.4. Floral bud differentiation characteristics
According to Fig. 2, the floral bud differentiation of E. grandiflo-rum 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 differenti-ation phase and pistil primordia differentiation phase. For differentresearch purposes, scientists used different standards in dividingflower bud differentiation process of lisianthus. For instance, Zaccaiand Edri (2002) revealed three distinct stages of floral bud develop-ment in ‘Heidi Deep Blue’, while Islam et al. (2005) divided flowerbud differentiation into 7 stages for ‘Fuji Deep Blue’. Moreover, thecultivar-dependent inconsistency in lisianthus floral bud differen-tiation also existed between the single-flowered ‘Fuji Deep Blue’and the double-flowered ‘Echo Blue’. For ‘Echo Blue’, it was difficultto distinguish between the second and/or third layer of petals andthe stamen initiation because the petals and stamens developedsimultaneously (Islam et al., 2005). These results also suggestedthat differences existed in the floral differentiation process amongvarious cultivars