title: Generation and multiplication of plantlets from callus derived from Haplopappus gracilus (Nutt.) Gray and their karyotype analysis.
abstract: Unopened flower heads of Haplopappus gracilis (2n = 4) provided primary explants for callus production and subsequent induction of organized growth.  Callus was initiated from small (3-5 mm in length) floral buds with benzylaminopurine (BAP) (44.4 micromoles; 10 mg/l) and naphthalene acetic acid (NAA) (0.54 micromole; 0.1 mg/l).  Lowering the BAP level to 4.44 micromoles (1 mg/l) but maintaining the NAA level, gave rise to organized but highly compressed shoot growing points from an otherwise undifferentiated callus mass.  Shoots selected from such cultures were maintainable and could be proliferated by growing 1-1.5-cm stem tip cuttings on Murashige and Skoog basal medium (solidified with agar) containing 0.444 micromole (0.1 mg/l) BAP and 0.054 micromole (0.01 mg/l) NAA.  The stem tip multiplication rates obtainable by these means permit reliable strategies for shoot multiplication or production of rooted plantlets.  Prolonged subculture and maintenance of shoots on growth regulator-free medium leads to in vitro flowering and greatly reduces rooting capacity.  Karyotype analysis of chromosomes from root tip cells at metaphase and chromosome measurements show that karyologically uniform plantlets (based on chromosome number and morphology) can be obtained.
authors.affiliation: Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794-5215, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Kann
authors.forename: S A
authors.initials: SA
authors.lastname: O'Connor
authors.forename: H G
authors.initials: HG
authors.lastname: Levine
authors.forename: A D
authors.initials: AD
authors.lastname: Krikorian
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D001593:Benzyl Compounds; D002875:Chromosomes / Q000235:genetics; D002999:Clone Cells; D003470:Culture Media; D046508:Culture Techniques; D007621:Karyotyping; D007701:Kinetin; D059828:Plant Cells; D063245:Plant Development; D010937:Plant Growth Regulators / Q000494:pharmacology; D018520:Plant Shoots / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D010944:Plants / Q000187:drug effects / Q000235:genetics*; D011687:Purines
chemical_list: D001593:Benzyl Compounds; D003470:Culture Media; D010937:Plant Growth Regulators; D011687:Purines; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin