Temperature is an important determinant of crop development rate (DR). Some reports have shown that the response of DR to temperature is nonlinear over a wide range. Others indicate that DR is affected by the amplitude of the diurnal temperature fluctuation. However, the nonlinearity between DR and temperature and the temperature amplitude effect are often confounded, as the amplitude effect can be explained by the nonlinearity. This paper investigates the effect of temperature amplitude per se on development to flowering in rice (Oryza sativa L.), using controlled-environment data for 16 cultivars. The response of DR to diurnally constant temperatures was quantified by a nonlinear model and subsequently used to predict days to flowering under diurnally fluctuating temperatures. The often large discrepancies between predicted and observed days indicated an effect of the diurnal temperature amplitude on DR. This effect was significant at different probability levels in 11 cultivars, but not in the other five (P > 0.10). The trend of this effect, where significant, also strongly differed among cultivars: temperature amplitude accelerated flowering in one cultivar but delayed flowering in others. The nonlinearity between DR and temperature and the effect of the temperature amplitude can explain a large part of the often observed variation among environments for thermal unit requirements for flowering.
Yin, X.; Kropff, M.J.; Ellis, R.H. Rice flowering in response to diurnal temperature amplitude. Field Crops Research (1996) 48 (1) 1-9. [DOI: 10.1016/0378-4290(96)00033-0]