An analysis of the effects of temperature and light integral on the vegetative growth of pansy cv Universal Violet (Viola x wittrockiana Gams)

Pansies (Viola x wittrockiana Gams.) cv. Universal Violet were sown on five dates between Jul. and Dec. 1992 and placed in six temperature-controlled glasshouse compartments set to provide mean temperatures between 6.5 and 30 degrees C. Shoot dry weight and leaf number were recorded. A model was constructed, to analyse the effects of light and temperature on dry matter accumulation, which assumed that relative growth rate (RGR) declined linearly with thermal time accumulated from sowing, reflecting ontogenetic drift. Furthermore, it assumed that RGR was a semi-ellipsoid function of temperature, rising to an optimum of 25.3 degrees C and declining thereafter, and a positive linear function of light integral. When fitted to data collected in this study the model accounted for 94% of the variance in RGR. Independent validation using data from four further crops grown in glasshouse compartments at four different set point temperatures showed that the model could also be used to predict plant dry weight accurately (r(2) = 0.98). The rate of mainstem leaf production was also linearly related to both light integral and temperature. (C) 1997 Annals of Botany Company.