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Browsing by Subject "vernalisation"

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  • Development of freezing tolerance and vernalisation in forage grasses in field experiments (2009–2013) 
    Korhonen, Panu (2014)
    Finland is the northernmost cultivation area in the world and the selection of forage grass species is mostly limited by long winters and short growing seasons. Forage grasses are usually grown as mixtures of species and produced intensively for silage. The grass species most commonly used in mixtures are timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis L.) which are both winter hardy species. As the climate changes in the future, more southern and more productive species like perennial ryegrass (Lolium perenne L.) and festulolium (Festuca sp. x Lolium sp.) may become more usable. The duration of snow cover has been predicted to shorten to 46 days in southern Finland by year 2050 (compared with 98 days at present). The autumns, when plants develop their tolerance against winter stresses, are also predicted to become warmer in the future. Changes in winter weather may also increase the frequency of problems such as plant exposure to freezing temperatures, associated with decreased snow cover and ice encasement due to fluctuating winter temperatures. This study presents the results of experiments carried out in Helsinki (Finland) between years 2009–2013. The experiments were done to assess the freezing tolerances and vernalisation of forage grasses and cereals hardened under field conditions. The vernalisation of plants was detected in all species as a decrease in days to heading during the vernalisation period. Perennial ryegrass and meadow fescue started flowering after the vernalisation was fulfilled during December-January. Winter cereals had already vernalised already in November. Hardening periods started at their earliest in the beginning of October. However, a deeper freezing tolerance developed during December in 2009–2010 and 2011–2012. During the winters of 2009–2010 and 2011–2012 hardening periods were long and hardening-induced temperature sums were the highest. During these winters the freezing tolerances were better in all species than during the other two winters.
  • Timotein (Phleum pratense ssp. pratense L.) alkuperän vaikutus kylmänkestävyyteen, vernalisaatiovaatimukseen sekä kasvuun ja kehitykseen 
    Luhtanen, Juha (2011)
    Forage crops are an important part of agriculture in worldwide since about 69 % of the agricultural area is covered with permanent meadows and pastures. In Finland forages cover up to 29 % of the agricultural area and production is based on intensive cultivation. The most cultivated species in Finland is timothy grass (Phleum pratense ssp. pratense L.). It is very frost resistant and that is why it is suited for northern growth environment. Timothy cultivars can be divided based on their genotypic origin to southern, northern and intermediate types. Cultivars differ in their growth and development habit. Along climate change extreme weather conditions become more frequent, mean temperature will rise and winters will be rainier. This research tries to find out how the different cultivars from different origins differ in their cold tolerance, growth and development speed and how vernalisation affects. Besides these it was researched if different methods for evaluating the vernalisation response in winter crops were useful methods to evaluate vernalisation response in forage grasses. Research composed two years long field trial and growth chamber trial. Vernalisation accelerated the growth and development of timothy. Based on this research the southern cultivars already had readiness for growth and development despite of the vernalisation if environmental conditions were favourable. Northern cultivars attained this readiness along the vernalisation. Vernalisation affected also to the architecture of the grasses. The number of generative tillers, that produce the inflorescence, increased due to vernalisation response. The number of vegetative tiller, not inflorescence tiller, became less due to vernalisation. The research revealed that cold tolerance was dependent on the temperature of the autumn hardening period (FH-COLD). High mean temperature during the hardening period decreased the cold tolerance. If the temperature was between 0 °C and + 5 °C cold tolerance increased. According to this research vernalisation had a clear effect on timothy growth and development for example. Northern cultivars do not necessarily need such a long vernalisation as Finnish winter is. Also methods for evaluating the vernalisation response in winter crops are partly useful in pure timothy cultivars too.

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