Effect of Light on Seed Germination of Eight Wetland Carex Species

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In wetland plant communities, species-specific responses to pulses of white light and to red : far-red light ratios can vary widely and influence plant emergence from the seed bank. Carex species are the characteristic plants of sedge meadows of natural prairie wetlands in mid-continental USA but are not returning to restored wetlands. Little is known about how light affects seed germination in these species-information which is necessary to predict seed bank emergence and to develop optimal revegetation practices. The effects of light on germination in eight Carex species from prairie wetlands were investigated. Non-dormant seeds of eight Carex species were used to determine the influence of light on germination by examining: (a) the ability of Carex seeds to germinate in the dark; (b) the effect of different lengths of exposures to white light on germination; (c) whether the effect of white light can be replaced by red light; and (d) whether the germination response of Carex seeds to white or red light is photoreversible by far-red light. Seeds of C. brevior and C. stipata germinated >25 % in continuous darkness. Germination responses after exposure to different lengths of white light varied widely across the eight species. Carex brevior required <15 min of white light for > or =50 % germination, while C. hystericina, C. comosa, C. granularis and C. vulpinoidea required > or =8 h. The effect of white light was replaced by red light in all species. The induction of germination after exposure to white or red light was reversed by far-red light in all species, except C. stipata. The species-specific responses to simulated field light conditions suggest that (a) the light requirements for germination contribute to the formation of persistent seed banks in these species and (b) in revegetation efforts, timing seed sowing to plant community development and avoiding cover crops will improve Carex seed germination.