Response of young spike differentiation and seed yield to planting density in Bromus inermis

In order to investigate the effect of densities on yield factors and spike growth, we use Bromus inermis ‘Wusu No.1’ as the material, and established three densities of sowing treatments (high density: sowing rate 26.67 kg·ha⁻¹; medium density: sowing rate 6.67 kg·ha⁻¹; low density: sowing rate 1.67 kg·ha⁻¹), which provided reference for the rational dense planting of B. inermiss seed field. The results showed that the differentiation process of young spikes was consistent between the medium density and low density treatments, and the differentiation cycle of young spikes in the high density treatment was 3 days later compare to the other treatments. Among the different agronomic traits, the number of tillers and reproductive branches were the highest in the high density treatment (P < 0.05), number of floret per inflorescence, number of seeds per inflorescence, number of spikelet per inflorescence, spike length, the seed setting rate and the thousand-grain weight were the highest in the low density treatment (P < 0.05). But the seed yield was highest in the middle treatment (P < 0.05), and the seed yield shows a extremely significant positive correlation with the number of flower per inflorescence and thousand-grain weight (P < 0.01). High levels of cytokinin and gibberellin content promoted the differentiation of young spikes during the differentiation of young spikes, and low levels of abscisic acid content in the later stage of differentiation was beneficial to promote the development of florets and improve flowers. The gray correlation analysis was carried out on the relevant physiological indicators in the differentiation process of the young spike of B. inermiss, and the order of influence of the differentiation process of the young spike of B. inermiss from high to low was cytokinin, gibberellin, leaf soluble protein, and abscisic acid.