Authors: Sershen Patricia Berjak N W Pammenter James WesleySmith
Publish Date: 2011/04/17
Volume: 249, Issue: 1, Pages: 171-186
Abstract
Effects of sequential procedures required for cryopreservation of embryos excised from the recalcitrant seeds of Haemanthus montanus were assessed ultrastructurally and in conjunction with respiratory activity and the rate of protein synthesis Fresh material water content 505 ± 092 g g−1 dry mass afforded ultrastructural evidence of considerable metabolic activity borne out by respiratory rates Neither exposure to glycerol nor sucrose as penetrating and nonpenetrating cryoprotectants respectively brought about degradative changes although increased vacuolation and autophagy accompanied both while respiratory and protein synthetic activity were not adversely affected Glycerolcryoprotected embryos flash dried to water contents 04 g g−1 showed organised ultrastructural features and considerable autophagy consistent with metabolic activity and although respiratory activity was lower protein synthesis rate was enhanced relative to fresh material However at water contents 04 g g−1 embryo tissue presented a mosaic of cells of variable density and ultrastructural status but trends in rates of respiration and protein synthesis remained similar Flash drying after sucrose exposure was accompanied by considerable ultrastructural abnormality particularly at water contents 04 g g−1 lysis of individual and groups of cells and considerable depression of respiration but not of protein synthesis Success assessed as ≥50 axes forming seedlings after cryogen exposure was obtained only when glycerolcryoprotected embryos at water contents 04 g g−1—in which the degree of vacuolation remained moderate—were rapidly cooled The outcomes of this study are considered particularly in terms of the stresses imposed by prolonged relatively slow dehydration and ultimate water contents on embryos showing considerable metabolic activity
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