Obligatory short-day plant, Perilla frutescens var. crispa can flower in response to low-intensity light stress under long-day conditions.

An obligatory short-day plant, Perilla frutescens var. crispa was induced to flower under long-day conditions when grown under low-intensity light (30 micromol m(-2) s(-1)). Plant size was smaller under lower light intensity, indicating that the low-intensity light acted as a stress factor. The phenomenon is categorized as stress-induced flowering. Low-intensity light treatment for 4 weeks induced 100% flowering. The plants responded to low-intensity light immediately after the cotyledons expanded, and the flowering response decreased with increasing plant age. The induced plants produced fertile seeds, and the progeny developed normally. The plants that flowered under low-intensity light had greener leaves. This greening was because of the decrease in anthocyanin content, and there was a negative correlation between the anthocyanin content and percent flowering. Treatment with L-2-aminooxy-3-phenylpropionic acid, an inhibitor of phenylalanine ammonia-lyase (PAL), did not induce flowering under non-inductive light conditions and inhibited flowering under inductive low-intensity light conditions. The metabolic pathway regulated by PAL may be involved in the flowering induced by low-intensity light.