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United States Department of Agriculture

Agricultural Research Service

Research Project: RESEARCH TO DEVELOP STRATEGIES AND TECHNOLOGIES FOR PRESERVING PLANT GENETIC DIVERSITY IN EX SITU GENEBANKS

Location: Plant Germplasm Preservation Research Unit

Title: Desiccation tolerance during different desiccation strategies in A. angustifolia embryos

Authors
item Pieruzzi, Fernanda -
item Floh, E.I. -
item Walters, Christina

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 29, 2011
Publication Date: N/A

Technical Abstract: Brazilian pine (Araucaria angustifolia) is native to the Atlantic Rainforest of Brazil and is an endangered species. The mature seeds are recalcitrant and have large embryos (about 2.5 cm in length) that contain more than 1 g H2O.g dry mass (dm)-1. Successful cryopreservation requires reduction of water content to a level that supports survival and allows sufficiently fast cooling to avoid freezing. The aim of this work was to evaluate the rate of drying and tolerance to desiccation of embryos using air, osmotic or chemical drying treatments. Embryos were dried using an air stream (i.e. “flash drying”), WPM medium containing 2 M of sucrose, or PVS2 cryoprotectant solution. Drying times were up to 12 h, 8 h and 2h for flash drying, medium supplemented with sucrose and PVS2 treatments, respectively. Embryos were divided into five segments after drying treatments to measure differences in drying rate. Middle sections resisted water loss more than the radicle tip or sections near the cotyledons. Embryos were rehydrated in WPM medium containing 1.2 M of sucrose. Flash dried embryos dried below 0.5 g H20.g dm-1 (12 h) showed visible signs of damage (browning and failure to rehydrate). Embryos dried to about 0.45 g H20.g dm-1 using 2 M sucrose recovered upon rehydration. Water content of embryos soaked in PVS2 after pretreatment with 2M sucrose decreased to 0.35 g H20.g dm-1. No further changes in water content were observed for middle sections or sections near the cotyledons. Sections closer to the radicle tip appeared to absorb PVS2, which gave the appearance of increasing water content with time. The amount of water remaining in the embryos after desiccation treatments is probably not low enough for successful cryopreservation of whole embryos. However, the embryo’s large size made it possible to use this species as a model to understand how cryoprotectants permeate into different tissues and affect their osmotic responsiveness and water freezing characteristics.

Last Modified: 8/30/2014
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