We have shown that low temperature activates the apoplastic route for sugar movement from the storage parenchyma cells into the apoplastic region of the bulb. Apoplastic sugars are then loaded to phloem and transferred to the developing bud. The absence of low temperature prevents the efflux of sugars into the apoplast, thus blocking further delivery to the bud. However, the proposed hypothesis is based mainly on the particular ontogenesis of the Corydalis tuber and the absence of a cytoplasmic route for sugar loading in this species, thus it cannot be directly extrapolated to all bulbous plants.