title: Somatic embryogenesis in pumpkin (Cucurbita pepo L.): control of somatic embryo development by nitrogen compounds.
abstract: Embryogenic cultures of pumpkin (Cucurbita pepo L.) were initiated from mechanically wounded mature zygotic embryos on 2,4-D-containing MS medium, and on hormone-free, semisolid modified MS medium containing NH4Cl as the sole source of nitrogen. The habituated line was derived from the embryogenic tissue induced with 2,4-D and maintained on medium without growth regulators. Sustained subculturing of the three embryogenic lines on a medium with NH4Cl as the sole source of nitrogen enabled the establishment of highly uniform cultures in which no further development into mature embryo stages occurred. The tissue consisting of proembryogenic globules or globular stage embryos was maintained, without decline, for over six years. Globular embryos proceeded to maturity when a combination of reduced (NH4) and unreduced (NO3) forms of nitrogen was provided in the medium. Different nitrogen sources in the medium caused changes of medium pH during subculture in the pH range of 4.0-6.5. The tissue growth and embryo development were blocked on medium with pH adjusted and stabilized at 4.0 or at 3.2.
authors.affiliation: Department of Molecular Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, HR-10000 Zagreb, Croatia.
authors.forename: Dunja
authors.initials: D
authors.lastname: Leljak-Levanić
authors.forename: Natasa
authors.initials: N
authors.lastname: Bauer
authors.forename: Snjezana
authors.initials: S
authors.lastname: Mihaljević
authors.forename: Sibila
authors.initials: S
authors.lastname: Jelaska
mesh_terms: D018929:Cell Culture Techniques / Q000379:methods; D028464:Cucurbita / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000254:growth & development*; D003470:Culture Media; D006863:Hydrogen-Ion Concentration; D017672:Nitrogen Compounds / Q000378:metabolism / Q000494:pharmacology*; D015053:Zygote
chemical_list: D003470:Culture Media; D017672:Nitrogen Compounds