Fig. 1. a–e. Responses of the four groups of H. vulgare genotypes shown in Fig. 2 to photoperiod duration in terms of the days to first node appearance (a) heading date (b and c), and relative earliness (d and e). The number of days to first node appearance (Dev31) was measured only for vernalized treatments. The number of days to heading (Dev49) and relative earliness were measured with and without vernalization. Group means followed by the same letter are not significantly different at the 0.05 probability level.