Trifluralin effects on tobacco callus tissue: Mitosis and selected metabolic effects

Inhibition of growth of pith callus of tobacco (Nicotiana tabacum, var. S-73) by the herbicide trifluralin (α,α,α - trifluoro - 2,6 - dinitro - N,N- dipropyl - p - toluidine) was previously observed. Inhibition of cell division in callus tissue of varying age by this herbicide was investigated using the Feulgen reagent and light microscopy. Upon staining and counting the number of cells in each phase of mitosis, a decrease in the number of cells in metaphase, anaphase, and telophase in the treated tissues was found. In addition to this reduction, arrested metaphases and multinucleated cells were observed. Similar results were observed with 10^?4M colchicine. The effects of trifluralin on incorporation of ¹⁴C-precursors into callus RNA, DNA, and protein were also investigated. Apparent RNA, DNA, and protein synthesis in callus were inhibited by trifluralin (5 × 10^?6M) treatment. The inhibition, however, was not expressed until 5–7 days after initiating treatment. Colchicine also affected apparent RNA, DNA, and protein synthesis; however, these effects were different than those observed with trifluralin. Incorporation of ¹⁴C-amino acids into protein was most severely inhibited by colchicine.