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

Abstract

The photoperiod marks a varied set of behaviors in plants, including bulbing. Bulbing is controlled by inner signals, which can be stimulated or subdued by the ecological environment. It had been broadly stated that phytohormones control the plant development, and they are considered to play a significant part in the bulb formation. The past decade has witnessed significant progress in understanding and advancement about the photoperiodic initiation of bulbing in plants. A noticeable query is to what degree the mechanisms discovered in bulb crops are also shared by other species and what other qualities are also dependent on photoperiod. The FLOWERING LOCUS T (FT) protein has a role in flowering; however, the FT genes were afterward reported to play further functions in other biological developments (e.g., bulbing). This is predominantly applicable in photoperiodic regulation, where the FT genes seem to have experienced significant development at the practical level and play a novel part in the switch of bulb formation in Alliums. The neofunctionalization of FT homologs in the photoperiodic environments detects these proteins as a new class of primary signaling mechanisms that control the growth and organogenesis in these agronomic-related species. In the present review, we report the underlying mechanisms regulating the photoperiodic-mediated bulb enlargement in Allium species. Therefore, the present review aims to systematically review the published literature on the bulbing mechanism of Allium crops in response to photoperiod. We also provide evidence showing that the bulbing transitions are controlled by phytohormones signaling and FT-like paralogues that respond to independent environmental cues (photoperiod), and we also show that an autorelay mechanism involving FT modulates the expression of the bulbing-control gene. Although a large number of studies have been conducted, several limitations and research gaps have been identified that need to be addressed in future studies.

Metabolite profile of two Allium cepa L. aggregatum group cultivars by Nuclear Magnetic Resonance

“…Sucrose is also the most abundant soluble carbohydrate in most onion cultivars (Pöhnl et al 2018). In recent research, carbohydrates were reported to be a factor influencing the bulb initiation and growth of Allium species (Atif et al 2020). A previous study also reported that abiotic stress tolerance in plants, especially drought tolerance, is correlated with carbohydrate metabolism.…”

Exogenous gibberellin and bulb size affect morpho-physiological traits and allicin content of Persian shallot (Allium hirtifolium Boiss.)

“…The effect of gibberellin on allium species, including onions and garlic has been reported in several papers (Geetharani et al, 2008;Ouzounidou et al, 2011). Currently, the application of gibberellin is considered as a new technique for enhancing the yield and improving propagation competence in garlic (Atif et al, 2020). The response of different organs of plants to the changes in gibberellin content is not similar since distinct parts of plants do not have the same sensitivity to this hormone (Martins et al, 2019).…”

Breaking the Dormancy of Snake’s Head Fritillary (Fritillaria meleagris L.) In Vitro Bulbs—Part 1: Effect of GA3, GA Inhibitors and Temperature on Fresh Weight, Sprouting and Sugar Content

“…Bulbs of F. meleagris, regenerated in vitro, also become dormant and cease growing, sprouting and forming leaves, if they had not been exposed to low temperature treatment [5]. Fritillary bulbs in vitro were inadequate for further morphogenesis if it was warm (24 • C) through the whole monitored period, similarly to many other geophytes [10]. Bulb regeneration in onion is well documented and controlled by day length and plant growth regulators (PGR), where gibberellic acid (GA 3 ) is crucial in this process [11,12].…”