Effects of red or far-red light and red/far-red ratio on the shoot growth and flowering of Matthiola incana

The effects of red light and far-red light on the main shoot elongation and flowering of long-day plant stock [Matthiola incana (L.) R. Br.] were compared. During the day, plants were covered with the films which convert light quality of sunlight into different red/far-red photon flux ratio, whereas at night the plants were irradiated with compact self-ballasted fluorescent lamps of red or far-red light. Plants exposed to high red/far-red photon flux ratio during the day and red light at night, flowered late. and developed short internodes, whereas the opposite occurred on plants grown under low red/far-red photon flux film during the day and irradiated with far-red light at night, i.e., flowering was advanced and internodes were elongated. The same findings were obtained regardless of planting date. However, the contrast between the two lighting conditions was especially apparent between autumn-sown, winter-cultivated plants, and summer-sown, autumn-cultivated plants because temperatures are colder during the winter flowering period. In this experiment, spring-sown, summer-grown plants had shorter internodes and more leaves; anthesis was advanced compared with plants sown at other times of the year. This finding will contribute to the efficient production of long-day flowering plant because advancing flowering by far-red light improves the utilization of the horticultural facilities by hastening crop turnover and reducing heating costs in winter.