Growth and Flowering Response of <i>Patrinia rupestris</i> in Response to Different Cold Durations and Photoperiods

Abstract

This study aims to examine the effects of cold durations and photoperiods on dormancy break, growth, and flowering of Patrinia rupestris native to Korea. First, we monitored the growth and flowering phenology of plants growing in an open field from March to October, 2018. For the dormancy breaking experiments, P. rupestris was maintained at 4°C for 0, 3, 6, 9, and 12 weeks under short-day conditions andfor cold treatment. The plants were then transferred to long-day conditions (9 h + 4h night interruption) in room chamber set at 25°C. To determine photoperiodic responses, P. rupestris was maintained under short- (9 h, SD), middle- (12 h, MD), and long-day (16 h, LD) conditions in room chamber set at 25°C following natural chilling accumulation. In open field conditions, P. rupestris blooms in the late summer from August to September with attractive yellow flowers. Time to first flower significantly decreased following 9 or 12 weeks of cold storage compared with the plants subjected to 3 or 6 weeks of cold storage. P. rupestris required ≥9 weeks of chilling treatment to achieve ≥33% flowering. Plant height was the highest in the LD condition (50.1 cm) compared with the SD (16.7 cm) and MD (16.1 cm) conditions. All plants grown under LD conditions flowered, but not all plants grown under SD and MD conditions did (0% flowering) after 16 weeks of forcing. P. rupestris demonstrated both obligate vernalization and long-day flowering responses.