title: Photoinhibition of germination in grass seed--implications for prairie revegetation.
abstract: Germination photoinhibition is not a recognized cause of revegetation failure; yet prolonged sunlight exposure can inhibit germination of several grass species. This research addressed susceptibility to photoinhibition of selected native grass species used to restore Canadian prairies, and reclamation treatments to alter environmental conditions in order to release seeds from photoinhibition. Under laboratory conditions effects of photoinhibition were tested on the ability of seeds to germinate at low water potential and effects of daily alternating temperatures and nitrates to break photoinhibition. Whether surficial mulch can release seeds from photoinhibition was assessed in a field experiment. Germination photoinhibition was evident in Festuca hallii and Koeleria macrantha seeds even under very low irradiances. The prolonged exposure to light decreased germination rates and ability of seeds to germinate at low water potentials. Daily fluctuating temperatures released a fraction of Bromus carinatus and Elymus trachycaulus seeds from photoinhibition yet did not improve F. hallii or K. macrantha germinability. Nitrates failed to break seed photoinhibition in all species tested. In the field experiment, mulched F. hallii seeds (covered with an erosion control blanket) showed a tenfold increase in germination percentages relative to seeds exposed to direct sunlight, indicating the facilitative effects of mulching on attenuation of the light environment. We conclude that germination photoinhibition as a cause of emergence failures in land reclamation where seed is broadcast or shallow seeded should be recognized and germination photoinhibition included in the decision making process to select revegetation seeding techniques.
authors.affiliation: Department of Renewable Resources, University of Alberta, 751 GSB, Edmonton, AB T6G 2H1, Canada; Land Reclamation International Graduate School, University of Alberta, 751 GSB, Edmonton, AB T6G 2H1, Canada; Departamento de Biología Aplicada y Alimentos, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, Capital Federal 1417, Argentina. Electronic address: mollard@ualberta.ca.
authors.forename: Federico P O
authors.initials: FP
authors.lastname: Mollard
authors.affiliation: Department of Renewable Resources, University of Alberta, 751 GSB, Edmonton, AB T6G 2H1, Canada; Land Reclamation International Graduate School, University of Alberta, 751 GSB, Edmonton, AB T6G 2H1, Canada. Electronic address: anne.naeth@ualberta.ca.
authors.forename: M Anne
authors.initials: MA
authors.lastname: Naeth
mesh_terms: D000383:Agriculture / Q000379:methods; D002170:Canada; D003247:Conservation of Natural Resources; D018525:Germination / Q000528:radiation effects*; D006109:Poaceae / Q000502:physiology / Q000528:radiation effects*; D012639:Seeds / Q000502:physiology / Q000528:radiation effects; D013472:Sunlight / Q000009:adverse effects*; D013696:Temperature; D014867:Water
chemical_list: D014867:Water
keywords: Cultural practices; Grassland restoration; Hydrotime model; Native grasses; Reclamation; Seedling emergence