How do non-adaptive grasses control growth cessation during autumn in high-latitude regions?

摘要

Use of perennial ryegrass (Lolium perenne) and xFestulolium is expected to increase in high-latitude regions due to milder winters and a prolonged growing season. One main challenge is inadequate growth cessation in autumn to allow sufficient cold hardening. Possible mechanisms behind this were examined by measuring photosynthetic activity and growth rate in triple-replicate field trials at two sites in Norway: Fureneset (59°N) and Vag0nes (67°N). Ten entries, including meadow fescue (Festuca pratensis), were investigated weekly from mid-September to early December 2011 using selected leaves (n = 10x3) of the regrowth after the third cut. Leaf growth rate (LGR) decreased with time and was significantly higher at Fureneset than Vag0nes. Photosynthetic acclimation before winter also differed at the two sites. A clear relationship between LGR and changes in photosynthetic apparatus was observed. In the south, relative light energy excess appeared to act as a signal triggering growth cessation, whereas in the north LGR was limited by the energy available for photosynthesis. Differing responses were also observed in northern- and southern-adapted meadow fescue cultivars.