Effect of Photoperiod on Germination of Cyperus inflexus Seeds

Seeds of the summer annual Cyperus inflexus Muhl. (Cyperaceae) are innately dormant at maturity in summer and autumn and require a period of moist chilling to break dormancy. Nondormant seeds do not germinate in darkness but germinate optimally in long days. In optimal daily photoperiods (12 h to continuous light at a light intensity of 2,100 lx), 10-14 (or more) cycles were required for maximum germination. When seeds were exposed to 1- or 4-h daily photoperiods (1 photoperiod per day), the percentage germination was greater in high (13,770 lx) than in low (1,372 lx) light intensities, whereas in a 20-h photoperiod or in continuous light seeds germinated better at the lower light intensity. The photoperiod response of C. inflexus seeds differed from other "photoperiodic" seeds with a chilling requirement for optimum germination in that completely afterripened (chilled) seeds of C inflexus responded to daily photoperiod, and the response was not temperature specific.