Clean **data** (127.29 Gb in total) were obtained from 18 libraries (2 treatments × 3 biological replicates × 3 developmental stages). According to the paraffin sectioning results, flower buds of either the control or GA 3 -treated group collected at 40, 80, and 140 DABT were in stage 3, 4, and 5, respectively (Fig. 2). Hence, we named these two sets of samples CK3-5 and GA3-5. Overall, the Q30 of all clean reads was >91%, with a GC content of 46.66-52.37. Detailed statistics of the clean reads are listed in Supplementary Data Table S1. Lacking a reference genome sequence of P. callosum, we de novo assembled the total clean reads, thus obtaining 157 463 unigenes having an average length and N50 length of 811.51 and 1282 bp, respectively (Supplementary Data Table S2). Principal component analysis (PCA) was performed for all samples spanning the flower developmental stages (Supplementary Data Fig. S3a). Except for stage 3, the other samples from different biological replicates clustered separately in the PCA biplot, following their distinct developmental stages.