RESUMO
BACKGROUND: Syzygium maire is a threatened tree species with limited information on long-term storage options for its recalcitrant seed. OBJECTIVE: To evaluate the cryopreservation of S. maire zygotic embryo axes (EA) using dehydration, encapsulation-dehydration as well as PVS2 vitrification using droplet vitrification (DV) and the novel droplet vacuum infiltration vitrification (DVIV) methods. MATERIALS AND METHODS: Excised naked and sodium alginate encapsulated EA were desiccated to various moisture contents (MC) using a laminar flow cabinet. Moisture content, embryo survival and plantlet formation, before and after cryopreservation, were assessed at 1 h intervals during the desiccation period (0-6 h). The influence of PVS2, using DV and DVIV, was assessed for various desiccation times and temperatures. RESULTS: Encapsulated EA desiccated to 31% and 37% MC survived but no plantlets formed following cryopreservation. Exposure to PVS2 using the DV method had a negative impact on embryo survival and plantlet formation, while DVIV resulted in improved results for non-cryopreserved EA. However, neither PVS2 vitrification method resulted in embryo survival following cryopreservation. CONCLUSION: S. maire embryos are sensitive to desiccation and likely require physical, chemical or a combination of protection methods to increase embryo survival and plantlet formation following cryopreservation.
Assuntos
Syzygium , Vitrificação , Criopreservação/métodos , Desidratação , VácuoRESUMO
The various sex and age components of Merino sheep flocks are analzed. Since a similar survey in 1965 the most significant difference is an increase from 40 to 52% of the mature female component. Various indicators point to an inability of the farmer to influence this slow rate of increase. The significant role which the prolonged retention of young Merino whethers on the farm plays in this respect is discussed. A higher percentage of rams during the mating period is also suggested.
