Sensitivity of brazilian-pine (Araucária angustifolia) embryos to desiccation and temperature

Abstract

The "recalcitrant" behavior of Araucaria angustifolia (Bert.) O. Kuntze seeds (Brazilian pine) limits the conservation of genetic resources of this important species in ex situ genebanks. As initial steps in developing storage protocols, we studied the interaction of water content and temperature on embryo survival. Embryos were excised from seeds and "flash-dried" to water contents as low as 0.29 g water/g dry mass and then exposed to 0°C, -5°C and -18°C for 4 h. Drying rate was calculated from drying time courses and expressed as (g water / g dry weight) / hour. Other authors have studied the effects of desiccation of whole seed of A. angustifolia on viability. In order to compare moisture content of whole seeds to that of embryonic axes, seeds of A. angustifolia were placed on the bench (25°C and 25%RH) and left to dry. Fresh weight of intact seeds and embryos excised from these seeds were also measured. Water contents were calculated and expressed on dry weight basis as g water / g dw. Increasing drying rate improved survival at lower water contents. Further, survival of embryos dried up to 0.29 g/ g and exposure to 25°C (25% survival) and 0°C (37.5% survival) suggests that cryopreservation using ultra-rapid cooling techniques may provide a method for long-term conservation of this important species. We suggest new studies towards technical approaches.