Some Effects of Triazines on Growth, Photosynthesis and Translocation of Photosjuthate in Pinus Species

The effects of triazines on growth, ¹⁴CO₂-fixation and translocation of ¹⁴C-assimilates by young Pinus seedlings were investigated. Post-emergenceroot application of moderate and high concentrations of simazine and atrazine resulted in severe toxicity to the seedlings of Pinus nigra and P. coniorta as depicted by reduction in dry weight, chlorosis, wilting and mortality. Atrazine was more toxic than simazine and P. nigra was more susceptible than P. contorta to both the triazines. Simazine treatment to the roots of P. nigra seedlings, not only caused inhibition of ¹⁴CO₂-fixation but also reduced the short-term downward transloca-tion of ^l4 C-assimilates. Various possible mechanisms whereby simazine reduced the downward movement of ^I4C-assimilates in Pinus seedlings are discussed.