An overview is given of the current knowledge of the genetic and physiological mechanisms underlying the morphological diversity exhibited by Gesneriaceae plants, one of the larger angiosperm families with more than 3200 species. The development of vegetative structures is highly diversified and includes several unusual features, such as anisocotyly, observed in some genera such as Streptocarpus or Monophyllaea, where one cotyledon develops continuously after germination to form phyllomorphs, rather than leaves. Some anisocotylous plants retain only the continuously developing macrocotyledon as photosynthetic tissue to form ‘one-leaf plants’. Recent Evo-Devo studies have shed some light on the origin and behavior of meristems in such phyllomorphic plants. The plant hormone, cytokinin and environmental factors, such as light, are likely to be the key players in this scenario. Reversions to vegetative development of floral meristems are observed in the genus Titanotrichum. Here, the flower meristems change to form bulbils at the end of the flowering season, a means of asexual mass reproduction. Both phenomena, anisocotyly and bulbil meristem formation are interesting cases of the diversification of meristem behavior in plants, which may be responsible for the generation of such high levels of phenovariation observed in Gesneriaceae.
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