Post-maturation treatment improves and synchronizes somatic embryo germination of three species of Japanese pines

Somatic embryos of three Japanese pines, Pinus thunberghii, P. densiflora, and P. armandii var. amamiana, were subjected to different post-maturation treatments to improve both germination and plant conversion frequencies. Slow desiccation of somatic embryos at high relative humidity resulted not only in a marked increment in germination frequencies but also subsequently improved plant conversion rates in all genotypes of the three species tested. Overall three species, germination and plant conversion frequency of somatic embryos was improved by more than fourfold (19–81%) and more than fivefold (15–77%), respectively, compared to those of untreated control. In addition, this treatment resulted in a considerable improvement of synchronization of the germination period. The time required for root emergence was synchronized over a half period (28–14 days) compared with the control. Somatic plants were acclimatized and their growth was monitored in the field.