Apical Development of Spring Barley under Field Conditions in Northeastern North America

Although the apical development of barley ( Hordeum vulgare L.) has been extensively researched, a complete description of spring barley apical development stages has not been published for continental North American field conditions. This study determined the timing and duration of the apical development stages, and the pattern and dynamics of spikelet primordium initiation. Data were collected for two barley cultivars for three successive seasons in eastern Canada. From the seedling stage to anthesis, apical development and the total number of primordia on the mainstem were monitored, and both were related to days after seeding (DAS) and to accumulated growing degree‐days (AGDD). The mainstem apex reached the double ridge stage 22 to 24 DAS (320–340 AGDD), awn initiation 40 to 42 DAS (≈650 AGDD), and anthesis 50 to 56 DAS (860–940 AGDD), with some variations among cultivars and years. Nine mainstem leaf primordia were initiated by 16 DAS. Spikelet primordium initiation was completed by awn initiation when 30 to 35 primordia had been formed. The data provide a description of barley apical development stages and indicate that spikelet primoridum production (i) occurs at a variable rate, (ii) is largely a function of thermal time, although genotype and climatic factors have some effect, and (iii) is related to time or thermal time in a curvilinear, rather than a linear fashion.