The interior atmosphere of storage facilities is very important for maintaining fruit quality and delaying senescence, so it's of significance to determine the volatile profiles in this environment for the postharvest industry. However, volatile profiles inside fruit storage facilities have been rarely reported. To study the volatile profiles of the atmosphere inside fruit storage facilities, a method comprising Monotrap^TM adsorbent and GC–MS analysis in the study was developed and tested. Based on that, the volatile profiles in the atmosphere inside fruit storage facilities at four locations in Shaanxi Province were monitored. Altogether thirty-six volatiles were detected, and most of them were identified as esters. An analysis of the similarities of volatile profiles showed that the three storage rooms at each location clustered together. The storage rooms at two locations in Baoji had the most similar volatile profiles, and both were similar to that at Xianyang, but different from that at Yan'an, which were consistent with their geographic distributions. On the basis of a principal component analysis, heatmap dendrogram, and correlation matrix analysis, these compounds clustered into five groups. Compounds in Group 1, which were abundant in the storage room at Yan'an, were branched-chain esters, whereas the compounds in the other four groups were mainly straight-chain esters which were abundant in the storage rooms at Xianyang and Baoji. The difference among volatile profiles inside fruit storage facilities at four locations might be caused by ultraviolet radiation. In this study, we demonstrated the Monotrap^TM adsorbent and GC–MS analysis were an efficient method for volatile compounds detection inside fruit storage facilities.

Brassinosteroid is an important hormone that interacts with auxin and gibberellin to regulate plant growth and development. However, there is currently a relative lack of information regarding brassinosteroid in apple. Previous study confirmed that exogenous brassinosteroid treatments increased growth and endogenous brassinosteroid, auxin, as well as gibberellin levels of apple nursery trees. Here we succeeded to find that exogenous brassinosteroid treatments upregulated the transcript expression of auxin biosynthesis, transport, and positive signal transduction genes as well as gibberellin biosynthesis genes. In contrast, the application of exogenous brassinosteroid downregulated the expression of genes encoding negative regulators of auxin and gibberellin signal transductions. Rapid responses of several brassinosteroid-, auxin-, and gibberellin- related genes to the brassinosteroid and brassinazole treatments inferred the crosstalk of BR and IAA or GA. Furthermore, the expression levels of cell growth-related genes were also enhanced by exogenous brassinosteroid. Auxin and gibberellin treatments also influenced growth of apple tree and enhanced the expression of brassinosteroid- and cell growth-related genes. These results indicate that the growth of apple tree is regulated by the interaction between brassinosteroid, auxin, and gibberellin. Our work opened new avenues for deep portfolio of apple tree growth and laid the foundation for future studies aimed at elucidating the mechanisms regulating hormone interactions-mediated growth in apple trees.