Short Day Induction of Inflorescence Initiation in Some Winter Wheat Varieties

Experiments in the Canberra phytotron with several European winter wheat varieties, especially cv. Templar, have shown that their need for vernalisation at low temperature can be replaced entirely by growth in short days at 21/16°C for the same period. In fact, although wheat is usually classified as a long day plant, inflorescence initiation at 21/16°C in unvernalised plants was twice as rapid in 8 h photoperiods as in 16 h ones. Short day induction was fastest in photoperiods of less than 12 h and was relatively insensitive to irradiance. Inflorescence development following initiation was faster the longer the photoperiod. At high irradiance, anthesis eventually occurred in 8 h days, but not at lower irradiance. These wheats are therefore short-long day plants, and may appear to be indifferent to daylength if only their time to anthesis is observed. Although short days can replace low temperatures, there are several important differences in their modes of action, and short day induction is better not referred to as short day vernalisation. Vernalisation of developing grains in the ear was more effective in long days.