Growth regulators and germination of recalcitrant seeds There is relatively little information avialable regarding the role of plant growth regulators in the germination of recalcitrant seeds. Pieruzzi et al. determine an increase in the ratio of the polyamines (spermidine + spermine) : putrescine in the embryos of germinating Araucaria angustifolia (gymnosperm) and Ocotea odorifera (angiosperm), which could be [...]