Ecophysiology of growth and flowering of four Korean native Veronica taxa in response to the photoperiod and cold treatment

Information of growth and flowering responses to vernalization and photoperiod is important for understanding the ecophysiology of native species. Plants of Veronica dahurica, Veronica pusanensis, Veronica kiusiana var. diamantiaca, Veronica pyrethrina, which are valuable ornamental plants native to Korea, were used to investigate whether Korean native Veronica species show distinct flowering responses to cold treatments and the photoperiod. Flowering in V. dahurica and V. pusanensis showed a facultative vernalization requirement with no responses to the photoperiod. V. kiusiana var. diamantiaca showed an obligate vernalization response for flowering, as a facultative long-day plant species. V. pyrethrina showed a facultative vernalization requirement for flowering, as a facultative long-day plant species. The four Veroncia species demonstrated different photoperiod and vernalization requirements for flowering; thus, the present study identified an interspecific variation in flowering requirements in this genus. We present the first classification of the flowering response type of Veronica species native to the Korean peninsula. Our findings offer reference data that may be useful in further studies of the physiological mechanisms in the genus Veronica and in developing conservation and cultivation strategies.