Plants of cocksfoot cv. Haka were taken just prior to the onset of winter and subjected to cold treatment at - 20-degrees-C temperature in laboratory. Panicle production and growth of the plants was analyzed after an 8-week growing period. Panicle number and dry weight of above ground phytomass was significantly smaller when plants were without a snow cover than when plants were under a 20 thick snow cover or under an ice cover. The negative effect was stronger on the number of panicles than on the above ground dry weight of phytomass. Growth and panicle production of plants which were under snow or ice cover did not differ significantly from the growth of control plants which were kept at +3-degrees-C temperature during the cold treatment. In the other study the stress caused by a lenghthly snow cover period was simulated by keeping flower-induced plants various time in the dark at + 10-degrees-C. This treatment caused exhaustion of plants reserve carbohydrates. In spring sampled plants a 28-day stress period decreased panicle production significantly compared to plants without stress. However, plants sampled in the fall did not respond negatively even to a 42-day stress period. The negative effect of the exhaustion of the plant's reserve carbohydrates was stronger on the number of panicles produced than on the above ground dry weight of phytomass. Both cold temperature during winter and excessively long snow cover are a greater risk to the panicle production ability in cocksfoot than to phytomass production. Proper winter hardening in the fall, and good condition of stand in the spring is particularly important to the cocksfoot seed production stand.
