Manipulation of flowering by cold temperature and photoperiodic control in Veronica nakaiana Ohwi, a korean endemic species.

Veronica nakaiana Ohwi is a Korean endemic species and has potential value as an ornamental and breeding resource of Veronica species. 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. nakaiana to 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. nakaiana is a day-neutral plant and requires a prolonged period of cold temperatures. In addition, the cold requirement showed an age-dependent response on flowering. [ABSTRACT FROM AUTHOR]