How do lilies open? The regulation of flower opening in lilies, and how to control it to improve post-harvest quality

Lilies are a commercial cut-flower crop highly popular in the UK for their large and colourful blooms. However, due to their perishable nature, cold/dark storage is necessary as part of commercial treatment to allow cut flowers to maintain their quality and developmental stage until purchase. Cold/dark storage has been shown to have an impact on the terminal bud’s ability to open in some varieties, particularly in stems with a greater number of buds per inflorescence. Understanding the opening process of lilies, and the endogenous and exogenous factors which may impact this process (particularly under commercial conditions) was an overarching aim of this project. Flower opening is driven by differential expansion or division of petal cells in other species, and firstly the mechanism of lily opening was characterised. Factors hypothesised to be affected by commercial treatment such as nutritional status (bud starch and soluble sugar content), time of opening, and secondary metabolism were confirmed to be significantly different between on plant and commercially treated lily buds. Position on stem was identified as a potentially important factor affecting the ability to open, nutritional status and bud metabolism over opening. RNA-sequencing was used to investigate expression patterns in buds which could open comparing to buds which failed to open as a result of commercial treatment-related stress. This differential expression analysis found several putative metabolic pathways associated with flower opening, alongside putative regulatory auxin and stress related elements. The phytohormone auxin was therefore explored as a potential treatment for commercial treatment-related stress due to its accelerating effect on lily opening and the correlated expression of auxin signal transduction components with lily opening. Overall, this work provides new insights into mechanisms of flower opening and indicates possible targets for improving commercially treated cut lily quality