title: Partial dehydration and cryopreservation of Citrus seeds.
abstract: BACKGROUND
  Three categories of seed storage behavior are generally recognized among plant species: orthodox, intermediate and recalcitrant. Intermediate seeds cannot be stored in liquid nitrogen (LN) without a previous partial dehydration process. The water content (WC) of the seeds at the moment of immersion in LN must be regarded as the most critical factor in cryopreservation. The purpose of this study was to investigate the basis of the optimal hydration status for cryopreservation of Citrus seeds: C. sinensis (sweet orange), C. paradisi (grapefruit), C. reticulata (mandarin) in LN.
  
  
  RESULTS
  To study the tolerance to dehydration and LN exposure, seeds were desiccated by equilibration at relative humidities between 11 and 95%. Sorption isotherms were determined and modeled; lipid content of the seeds was measured. Seed desiccation sensitivity was quantified by the quantal response model. Differential scanning calorimetry (DSC) thermograms were determined on cotyledon tissue at different moisture contents to measure ice melting enthalpies and unfrozen WC. Samples of total seed lipid extract were also analyzed by DSC to identify lipid transitions in the thermograms.
  
  
  CONCLUSIONS
  The limit of hydration for LN Citrus seeds treatment corresponded to the unfrozen WC in the tissue, confirming that seed survival strictly depended on avoidance of intracellular ice formation.
authors.affiliation: Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA), CONICET, Facultad de Ciencias Exactas, UNLP, 47 y 116, La Plata (1900), Argentina. natalia@quimica.unlp.edu.ar
authors.forename: Natalia
authors.initials: N
authors.lastname: Graiver
authors.forename: Alicia
authors.initials: A
authors.lastname: Califano
authors.forename: Noemí
authors.initials: N
authors.lastname: Zaritzky
mesh_terms: D000383:Agriculture / Q000379:methods*; D002152:Calorimetry, Differential Scanning; D002957:Citrus / Q000737:chemistry / Q000254:growth & development; D032083:Citrus paradisi / Q000737:chemistry / Q000254:growth & development; D032084:Citrus sinensis / Q000737:chemistry / Q000254:growth & development; D018548:Cotyledon / Q000737:chemistry / Q000254:growth & development; D015925:Cryopreservation; D003890:Desiccation; D004058:Diffusion; D018525:Germination; D008055:Lipids / Q000032:analysis / Q000737:chemistry; D008954:Models, Biological; D044367:Phase Transition; D010936:Plant Extracts / Q000737:chemistry; D012639:Seeds / Q000737:chemistry / Q000254:growth & development; D013045:Species Specificity; D014867:Water / Q000032:analysis*
chemical_list: D008055:Lipids; D010936:Plant Extracts; D014867:Water