The proof is in the bulb: glycerol influences key stages of lily development

Abstract

A bulb is a whole plant condensed into an underground organ. A geophyte's bulb comprises both food reserves and important developmental history that may affect its whole growth. In Easter lily (Lilium longiflorum), bulb size is associated with the plant's flowering pathwayvernalization or photoperiodand also affects sprouting, flower quality and abortion rate. The aim of this study was to investigate the reasons for the major physiological differences between large and small bulbs. Lily bulbs start their development from secondary meristems along the stem, with large bulbs being heavier and bear more scales than small ones. Peeling the outer scales of a large bulb converts its physiological responses into those of a small bulb, implying that the physiological discrepancies in plants developing from large or small bulbs are mediated by factors inherent to the bulb. We therefore performed broad analyses of the metabolite composition in the scales of bulbs subjected to temperature regimes affecting further plant development. We found a striking association between the level of glycerol, a primary metabolite mostly synthesized in the outer scales, and a delay in sprouting and flowering time, and reduction in abortion rate. Exogenous glycerol application to the bulbs before planting corroborated these results. Moreover, transcriptome analyses showed that flowering-promoting gene expression was downregulated in the bulb after glycerol treatment, while potential flowering inhibitor as well as a dormancy-related gene expressions were upregulated. Based on these studies, we postulate that glycerol is a major factor influencing both vegetative and reproductive development in lily.

Bulbous perennials precisely detect the length of winter and adjust flowering dates

“…However, it is likely that the molecular mechanism of vernalization and its role in flowering adjustment is quite different. In Arabidopsis , the winter cold is mainly required to down‐regulate FLC ( Flowering Locus C ) flowering repressor (Bouché et al ., 2017; Antoniou‐Kourounioti et al ., 2018; Hepworth et al ., 2018), while the molecular mechanisms of vernalization are different in bulbous taxa (Lee et al ., 2013; Lazare et al ., 2019; Wang et al ., 2019). However, it was also suggested that increased auxin sensitivity of the bulb induced by a long cold period is a critical common element for the vernalization of several bulbous taxa (Khodorova & Boitel‐Conti, 2013).…”

Mechanism of Allium Crops Bulb Enlargement in Response to Photoperiod: A Review

“…Environmental factors, such as for example the day length, affect bulb enlargement and taste eminence in onion [33]. In onion, light range and quality impacts bulb formation and quality [34][35][36][37][38][39][40][41]. The bulb initiation and growth of further Allium species including garlic have been shown to be influenced by day length, temperature, and carbohydrates [42,43].…”

Expression of LhFT1, the Flowering Inducer of Asiatic Hybrid Lily, in the Bulb Scales

“…In L. longiflorum, cold exposure is not an obligatory prerequisite for flowering, as an alternative flowering pathway can bypass vernalization in small bulbs (Lazare and Zaccai, 2016). Recently, the levels of glycerol in L. longiflorum bulbs was found to be associated with a delay in sprouting and flowering time and a reduction in abortion rate (Lazare et al, 2019).…”