The influence of photoperiod on barley development

Abstract

Time to awn emergence and leaf number on the main culm were recorded for 10 barley cultivars grown under a short and long photoperiod after 4 weeks cold treatment at 4°C; the appearance of leaves on the main stem was also recorded at regular intervals. There were differences among the cultivars for photoperiod response and the duration of the basic vegetative phase. Photoperiod response tended to be complementary with basic vegetative phase, as one increased the other decreased and vice versa. Leaf appearance generally did not differ significantly between photoperiod treatments. In the short day, leaf appearance continued for a longer period with more leaves produced on the main stem. Leaf appearance as a function of time was best described by a cubic or a quadratic exponential polynomial function. The absolute rate of leaf appearance (leaves d−1) under short day showed an increase to a maximum followed by a decrease to a minimum and then a further increase. Under long day, three patterns of absolute rate of leaf appearance were evident. There was a rapid increase to a maximum followed by either a rapid or more gradual decline; in several cultivars the pattern was similar to the one seen for the cultivars in the short day treatment, although it was somewhat truncated. The significance of photoperiod response and basic vegetative phase are discussed in relation to crop adaptation and the change in the absolute rate of leaf appearance is discussed in relation to the stage of plant development.