02965nam a2200445 a 450000100080000000500110000800800410001910000210006024501290008126000500021030000100026050000180027052018350028865000090212365000130213265000140214565000110215965000180217065000220218865000090221065000090221965000160222865000170224465000120226165000110227365000110228465300100229565300200230565300150232565300280234065300170236865300200238565300160240565300180242165300180243965300130245765300210247065300140249165300140250511495182023-03-10       1999    bl uuuu  m   00u1 u    #d1 aSANTOS, I. R. I.  aDesiccation and freezing tolerance of embryonic axes and lateral buds of Citrus sppbimplication for germplasm conservation.  aFort Collins: Colorado State Universityc1999  a159p.  aPh.D. Thesis.  aCitrus is the second most importan fruit crop in the world in terms of economic value. Germplasm conservation of commercial cultivars as well as of wild relatives is a priority. Presently, Citrus germplasm has been preserved mainly in field gene banks. Plants maintained in the field are susceptible to biological and climati disasters. Cryopreservation (conservation in liquid nitrogen at -196oC or in its vapor phase at - 150oC) can in theory ensure storage of plant material for several years maintaining high biological and genetic integrity. This research examined several aspects of tolerance to desiccation and freezing in an attempt to develop cryopreseravation protocols for embryonic axes and lateral buds of Pineapple sweet orange (Citrus sinensis [L.] Osb.) and for embryonic axes of Citrus limon Burm. F. and Citrus reticulata Blanco. The roles of alginate encapsulation and pre-culture with sucrose in enhancing tolerance of freezing in liquid nitrogen were tested. Carbohydrate analysis was carried out on axes pre-cultured with sucrose or not and on buds from cold acclimated plants to gain insight on the role of sucrose as a cryopreservation stabilizer. The interrrelationshisp between water content and thermodynamic properties of water during freezing and thawing, which are critical in achieving survival in liquid nitrogen, were also studied. Prior to cryopreservation studies the germiantion of isolated embryonic axes was assessed. For that, embryonic axes with and without alginate encapsulation and with and without sucrose pre-culture, but without dehydration or exposure to liquid nitrogen, were cultured in vitro. Total seedling recovery was observed whether or not axes had been encapsulated and whether normal seedlings, without intermediary callus formation, within three weeks of culture in vitro.  abuds  afreezing  agermplasm  alemons  aConservação  aCriopreservação  aFrio  aGema  aGermoplasma  aLaboratório  aLaranja  aLimão  aPlanta  aCitro  aCitrus reticula  aCitrus spp  aCongelamento Tolerancia  aConservation  aCryopreservatio  aDesiccation  aDessidratacao  aEmbriogenesis  aOrganges  aPlant laboratory  aProtocolo  aTolerance