FACTORS AFFECTING PANICLE PRODUCTION OF COCKSFOOT (DACTYLIS-GLOMERATA L) IN FINLAND .4. RESPONSE TO FROST AT PANICLE GROWTH-PHASE

Frost treatment after floral initiation decreased the number of panicles in cocksfoot. The effect was strongest by a -10-degrees-C frost treatment but treatments at -6-degrees-C and -3-degrees-C also had a significant negative effect on panicle number. Panicle production of cocksfoot was more sensitive to frost injury at the late stage of development than at the early developmental stage. The production of above ground phytomass was not as sensitive to frost injury as panicle production. It was difficult to detect the immediate injury caused by frost even in the small pots. At the panicle in boot stage a -7.9-degrees-C (soil surface) natural frost occurred destroying about one half of in boot panicles in an undense first year stand, and about one-third in a dense second year stand. Because of the early development of cocksfoot panicles and the frequent occurrence of spring frosts in Finland, frost is an important risk to cocksfoot seed production in Finland. The extent of frost damage to seed yield depends on the likelihood of new tillers substituting panicle production in frost-damaged tillers,