Chronological events unfolding the vegetative and floral phenology of apical bud in Crocus sativus.

Saffron (Crocus sativus L.) is an infertile perennial geophyte considered the most expensive spice in the world. Seasonal fluctuations and climate change have significant impact on the growth, development, and yield of saffron stigma, which is the economically valued part of plant. The stigma being part of the flower, the knowledge of phenotypic transition from dormant apical bud up to flowering is vital, yet, not explored properly. The complexity of flowering in C. sativus further accentuates by the lack of clear demarcation between flowering and non-flowering corms in terms of weight and sizes, as small corms are known to be vegetative only, while large ones produce flower. Therefore, chronological phenotyping on a weekly and quarterly basis of apical shoot and flowering primordia between June and October was carried out to understand the organogenesis sequentially. In large corms, the stamen was the first floral organ to initiate followed by the formation of tepal from the base of the stamen. The plants exhibited both synanthous and hysteranthous flowering. Untargeted metabolome analysis of dormant apical bud just before dormancy break from flowering buds from large corms as well as non-flowering buds from small corms identified the presence of many differentially accumulated metabolites including sphingosine and meglutol. Key metabolites such as phytosphingosine, 3-hydroxy-3-methyl glutaric acid, 3-acetamidopropanal, 6-hydroxykynurenic acid, D-serine, and 1-D-myo-inositol 3-phosphate were also detected having associated with isoprenoid biosynthesis, lignin pathway regulation, and carbohydrate metabolism that participates in flowering. The integration of morphological, histological, and metabolomic data offers a comprehensive view of the flowering process that can be utilised in future biotechnological interventions in C. sativus.