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Veronica nakaianaOhwi is a Korean endemic species and has potential value as an ornamental and breeding resource of Veronicaspecies. Therefore, it is necessary to determine the environmental factors for floral induction to manipulate flowering for the industrial application of this plant. This study was conducted to investigate the flowering response of V. nakaianato cold temperatures and photoperiod treatments. In Expt. 1, six-week-old seedlings were treated with a cold temperature of 5 °C for from 0 to 12 weeks. After the artificial cold treatments, the plants were subjected to the following photoperiod treatments: 9/15, 12/12, 14/10, 16/8, or 24/0 (day/night) h. In Expt. 2, seven-month-old plants were transferred to an open field for natural cold treatments and the chilling hours were calculated to quantify the flowering response to cold temperatures. In Expt. 1, the photoperiod does not affect the percent flowering or flowering time. The plants flowered only after artificial cold treatments lasting for more than eight weeks. However, the average percent flowering was less than half. In Expt. 2, although flowering was also observed only after more than eight weeks of natural cold treatment, the percent flowering in Expt. 2 was higher than that in Expt. 1. In both experiments, the number of days to flowering significantly decreased with increasing the cold treatment period. These results indicated that V. nakaianais a day-neutral plant and requires a prolonged period of cold temperatures. In addition, the cold requirement showed an age-dependent response on flowering.

This study was conducted to examine the flowering responses of Eremogone junceato photoperiod (Experiment 1) and chilling treatment (Experiment 2). In addition, plants were subjected to cold storage following chilling treatment to extend the flowering season (Experiment 3). In Experiment 1, naturally chilled E. junceaplants were subjected to five different photoperiod conditions (9/15, 12/12, 14/10, 16/8, and 24/0 h). There were no differences in percent flowering among photoperiod treatment groups. Furthermore, these plants showed no significant differences among groups in the number of days to the first open flower. In Experiment 2, the plants were exposed to natural chilling for 0, 4, 8, or 12 weeks or artificial chilling at 5 °C for 0, 4, or 8 weeks. Percent flowering was less than 30% in the no-chilling treatment but increased with increasing chilling duration in both the natural and artificial chilling treatments. Days to the first open flower declined as the chilling duration increased. To quantify the chilling requirement, chill units (CUs) were calculated using a modified chilling hours model (MCHM) and a modified Utah model (MUM). To exceed 80% flowering, at least 1,854 CUs in MCHM or 1,889 CUs in MUM were required. In Experiment 3, naturally chilled E. junceaplants were stored for 0, 4, 8, or 12 weeks at 0 °C. Percent flowering significantly decreased under all cold storage treatments. However, cold storage treatment did not affect the number of days to visible bud or days to the first open flower. These results indicate that, although percent flowering was reduced by cold storage, the flowering season could be extended by storage treatment. In conclusion, E. junceacan be classified as a day-neutral plant with a chilling requirement for flowering. Moreover, artificial chilling treatment and cold storage can be used to advance or postpone the flowering season for year-round cultivation.

This study investigated the effects of daily light integral (DLI) on the photosynthesis, growth, and flowering of Veronica rotundavar. subintegraand V. longifolia. Six-week-old seedlings with four or five nodes were grown under five average DLI levels (3.6, 6.6, 8.1, 14.7, and 18.3 mol m−2d−1) in a greenhouse. Both species grown under DLI conditions of over 8.1 mol m−2d−1showed a lower maximum quantum efficiency (Fv/Fm) than those grown under DLI conditions of 3.6 and 6.6 mol m−2d−1after 2 weeks of treatment. However, these differences diminished after 6 weeks of treatment. In the light response curve, the net CO2assimilation rates (An) for light intensities of 200–1200 μmol m−2s−1increased with increasing DLI. Most growth parameters, including plant height, number of branches, stem diameter, and chlorophyll contents of both species, were promoted with increasing DLI. Although increasing DLI did not affect the percent flowering in either species, the number of nodes below the first inflorescence was lower under higher DLI conditions. The number of visible inflorescences (VIs) and inflorescence length of the first open flower showed similar trends as the growth parameters. The parameters associated with days to flowering were shortened as DLI increased. These results suggest that high DLI conditions could promote the growth and flowering of two Veronicaspecies by increasing Anand that they can be used to force flowering of these plants in commercial production.

Veronica rotundavar. subintegra(Nakai) T. Yamaz. (mountain spike speedwell) and V. longifoliaL. (long-leaf spike speedwell) are Korean native plants that have potential value as novel ornamental crops due to their unique appearance and flowering time. This study was conducted to examine the effects of cold and photoperiod treatments on the growth and flowering of two Veronicaspecies. Eight-week-old seedlings with four or five nodes grown under a 9-h photoperiod were stored at 5 °C for 0, 3, 6, 9, or 12 weeks and then forced under one of six photoperiod conditions [9, 12, 14, 16, or 24 h of continuous light or 9 h with a 4-h night interruption (NI, 22:00 to 02:00 HR)] in a greenhouse. Regardless of cold treatment, there were no significant differences among photoperiod treatments in any growth parameter (i.e., plant height, numbers of nodes or branches, leaf length or width, shoot or root dry weight) in either species. In plants without cold treatment, V. rotundavar. subintegrashowed more than 85.7% flowering regardless of photoperiod, and flowering of V. longifoliawas 80.0, 66.7, 70.0, 85.7, 71.4, or 100.0% under photoperiods of 9, 12, 14, 16, or 24 h or NI, respectively. The number of nodes below the first inflorescence, the number of visible inflorescences (VI) at the first open flower, and days to VI were not influenced by photoperiod in either species. As a result, cold treatment was not necessarily required for the flowering of the two Veronicaspecies. Moreover, photoperiod also did not affect the flowering of either species. These results indicate that the two Korean native Veronicaspecies can be classified as day-neutral plants with no vernalization requirement.