Abstract:The leaves of Oxalis triangularis ‘Purpurea’ have significant nocturnal movement, which is characterized by a circadian rhythm of opening and closing. The effects of light quality, duration, and vibration on nocturnal movement of Oxalis were investigated in a climate chamber with controlled light and a time-laps camera. The results showed that light wavelength was a critical factor for the nocturnal movement pattern of Oxalis. The longer the wavelength, the faster the leaf unfolds, the shorter the wavelength, the slower the leaf closure. Under continuous light for 3 days, the leaves did not close, except that the leaves opened and closed only at 18:00 under red light. When 12 h/12 h (light/dark) photoperiod lasted for 3 days, it took 45-61 min for the leaves to unfold in the morning and 85-120 min to close completely at night. The leaves had unfolded before 8:00 AM except white light. The leaves could still unfold for 3-5 h every day under continuous dark. Horizonal rotation could change the nocturnal movement pattern of Oxalis. When the leaves were rotated at 300 r/min for 0.5-6 h, it will not close completely during rotation, only close to about 60°. The longer the rotating time, the faster the rate of leaf closure after stopping rotation. When rotation stopped after 2 h, the leaves would not close, so there was a certain range of adaptability to external stress of Oxalis. Therefore, when applying O. triangularis ‘Purpurea’ in the garden, short-wavelength illumination could be used to extend the unfolding time of leaves, increase its ornamental effect, and avoid exposure to the sun at noon.
