Response to Daylength in Oats: Pre-Anthesis Development and Set of Spikelets and Florets

Daylength ranges between 15 h and 22 h when oats are sown in Finland. This study evaluated the effect of 15-h, 18-h and 24-h daylengths on apical development, pre-anthesis growth, and spikelet and floret set in two oat cultivars ( Avena sativa L.) adapted to northern growing conditions. Experiments were done in a growth chamber at 18°C.
Increases in daylength shortened the period of apical development. The oat cultivars were especially responsive to increase in daylength from 15 h to 18 h. The increase in daylength resulted in a 45 % reduction in number of fertile florets and a slight increase in the proportion of incompletely development and stunted florets. Fertility of florets was most reduced on the lower primary and secondary branches of the panicle. Total number of leaves and phyllochron decreased as daylength increased. Moreover, the longer the day, the lower the number of green leaves per main stem until developmental stage 11. However, at pollination, oats exposed to 15-h days had the lowest number of green leaves. Results of study indicated that delayed sowing, when associated with longer days at pre-anthesis, hastened apical development and decreased yield potential in oats.