Effect of Trifluralin on Growth, Morphology, and Nucleic Acid Synthesis

Roots and shoots of corn seedlings (Zea mays L. var. Dixie 18) germinated in trifluralin (alpha,alpha,alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) solutions are characterized by radial enlargement of the cortical cells and by multinucleate cells in the meristematic regions. Trifluralin inhibits elongation of Avena coleoptile sections at concentrations of 0.1 mum to 10 mum. Synthesis of DNA, RNA, and protein is suppressed in the root tips while no significant effect is noticeable in the shoots of corn germinated in trifluralin. A (32)P time-course study of 48, 72, and 96 hours utilizing phenol extraction and MAK column separation of corn root and shoot nucleic acids showed suppression of (32)P incorporation in the treated roots; however, the 72 and 96 hour treated shoots incorporated a much greater amount than the control with most of the increased incorporation found in the sRNA and DNA fractions. The increased activity in the DNA may be due to a high G-C type DNA. No selective suppression or enhancement of any particular RNA species was noticed in the treated plants.