Reanalysis of vernalization data of wheat and carrot

Vernalization is an important determinant of the growth, development, and y ield of biennial and perennial crops. Accurate simulation of its response t o temperature is thus an important component of successful crop systems mod elling. Vernalization has a low optimum temperature compared to other tempe rature responses of plants, and thus may be difficult to treat using expres sions that are appropriate for other plant processes. This paper examines t he application of a simple equation that has been used for other processes. It reads as v = V-max (T-max-T/T-max-T-opt)(T/T-opt)T-opt/T-max-T-opt, whe re v is the daily rate of vernalization progress at temperature T, T-opt an d T-max are the optimum and maximum temperatures for vernalization, respect ively, and V-max is the maximum daily rate of vernalization (the inverse of the minimum number of days required to complete vernalization), which occu rs at T-opt. The model was applied to published vernalization data for whea t and carrot. The fits to data were good (adjusted R-2 for wheat of 0.94. f or carrot 0.98), with estimated T-opt and T-max being 5.7+/-0.5 and 21.3+/- 0.4 degrees C, respectively, for wheat 'Norin 27' and 6.6+/-0.2 and 14.1+/- 0.3 degrees C for carrot 'Chantenay Red Cored'. The estimated parameters, i n particular the high T-max for wheat, were close to those reported using d ifferent analytical approaches. It was suggested that the function would be useful for summarizing vernalization data, and that its use would avoid th e abrupt changes that are inevitable when different linear relationships ar e used for part of the overall response. It was also suggested the high T-m ax should be taken into account when interpreting data obtained with wheat grown under warm conditions. (C) 1999 Annals of Botany Company.