Temporal and spatial effect of low pre-planting temperatures on plant architecture and flowering in bolting garlic

Garlic flowering and bulbing are prone to photo-thermal regulation during its annual cycle. As in many other geophytes, these pathways are parallel but competitive, and can be manipulated by the environment. Both flowering and bulbing are of paramount physiological value, and of great horticultural interest. We argue that, in bolting garlic, differential regulation of only one of the two pathways by pre-planting vernalization is unfeasible, and that garlic's response to cold shows an optimal curve. Within limits, long vernalization treatments have resulted in rapid development of ‘Reproductive and Bulbing Phenotype’ with fast leaf elongation, early transition of the apical meristem to the reproductive state, development of axillary buds, flowering and bulbing. Low temperatures trigger primary signaling components, thus modulating organogenesis even under a relatively short photoperiod. We therefore propose that under a suboptimal photoperiod, favorable temperatures could substitute the plant's requirements for photoperiod and signal for the meristem transition, flowering and bulbing. The optimum response of the studied genotype was obtained after vernalization of four weeks at 4 °C. No transition of the apical meristem was evident in plants exposed to only short or no vernalization, namely the apex remained vegetative. These plants continuously produced foliage leaves, thus forming a “Leafy Phenotype” which did not branch, bulb or flower. Comprehension of the plant's response to environment is expected to facilitate physiological manipulations on the production of either bulbs or true seeds in garlic.