title: Differences in responses of plant hairy roots to chemical toxicity compared between primary and ramified roots.
abstract: As a bioassay system for the assessment of the chronic toxicity of chemicals, successive culturing of pak-bung hairy roots was conducted with serial passaging of the primary and lateral root tips. Based on the elongation rates of these root tips, the dose-response profiles were examined while exposing the roots to 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) at concentrations of 0.01-3.0 micromol/dm3, and the values of the median effective concentration, EC50, were determined under the conditions examined. Irrespective of the test chemicals, the EC50 values of both the primary and lateral roots gradually decreased with increasing exposure period ranging from 7 to 35 days. A marked difference in the EC50 values was observed between the primary and lateral roots exposed to 2,4-D; the EC50 value of the lateral roots following exposure for 35 days was 0.036 micromol/dm3, which was one-eighth that of the primary roots for the same exposure period. Moreover, it was found that this phenotypic difference in the root responses was consistently reflected in the distinct patterns of DNA fingerprints of the primary and lateral roots analyzed by the random amplified polymorphic DNA method.
authors.affiliation: Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Ninomiya
authors.forename: Motomu
authors.initials: M
authors.lastname: Nishioka
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kino-oka
authors.forename: Masahito
authors.initials: M
authors.lastname: Taya
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000633:toxicity*; D001681:Biological Assay / Q000379:methods; D018744:DNA, Plant / Q000032:analysis; D006540:Herbicides / Q000633:toxicity*; D027741:Ipomoea; D018519:Meristem / Q000187:drug effects / Q000254:growth & development; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D009153:Mutagens / Q000633:toxicity*; D018517:Plant Roots / Q000187:drug effects* / Q000254:growth & development; D019105:Random Amplified Polymorphic DNA Technique
chemical_list: D018744:DNA, Plant; D006540:Herbicides; D009153:Mutagens; D008769:Methylnitronitrosoguanidine; D015084:2,4-Dichlorophenoxyacetic Acid