Developmental stages of young spikes in six-rowed qingke (Hordeum vulgare L.)

The number of seeds per spike of qingke barley is one of the primary factors contributing to its associated economic output, and the development process of young spikes affects the resulting number of grains. Therefore, the differentiation and development processes of qingke spikes represent vitally important milestones in the formation of qingke yields. Nevertheless, the developmental course of qingke spikes has not yet been well characterized. In this study, we first systematically divided the development process of young spikes into 10 landmark stages. These periods spanned from the one-leaf stage to the ten-leaf stage, and we analysed the phenological characteristics of the spikes at each stage. Each spike was composed of axis and spikelet. Each spikelet contained one floret, which had a pair of rudimentary glumes (sterile lemmas), two interlocking large glumes (lemma and palea), an awn, a similar rudimentary axis, a pistil, three stamens, and two lodicules. In this research, we ascertained the patterns for the differentiation and development of young spikes, which provides a reference and theoretical basis for further research on qingke production and reproductive biology.