Assesment of plant tolerance to phenoxy and triazinic herbicides

CUADRADO, V; MERINI, LJ; FLOCCO, CG; GIULIETTI, AM

Valparaiso - Chile

Congreso; 12th International Biotechnology Symposium and Exhibition.; 2004

Maize and alfalfa are two of the most important agricultural plants in Argentine. Before or after the seeding, herbicides are applied to soil as preemergence or postemergence treatments. Excessive permanence of these xenobiotics in soil, due to their physicochemical properties and extensive use, may be detrimental and carry the risk of ground water contamination. As a first attempt to investigate the possibility of phytoremediation of soils using maize and alfalfa, we make in vitro assays to evaluate the tolerance of these plants to phenoxy and triazinic herbicides (2,4-D and atrazine, respectively). The experiment consisted in seedlings on agar medium with different concentrations of the herbicides. The range of concentrations was estimated considering: field application rates and values observed in contaminated soils and waters. In order to eliminate the possible effects of the indigenous microflora, the seeds were surface sterilized. Afterwards, they were sown in 360 ml glass flasks on Murashige-Skoog medium containing 10 g/l sucrose, 4 g/l agar and different concentrations of atrazine or 2,4-D. Incubation was carried out at 24±2 ºC, under a 16/8 h photoperiod. After 10 days for maize and 13 days for alfalfa, the individual seedlings were harvested, washed and the following tolerance parameters were evaluated: root length, shoot length, shoot fresh weight and percent germination. The results showed a more marked toxic effect of 2,4-D in comparison with that of atrazine. 2,4-D concentrations of approximately 0.1 ppm and between 0.01-0.05 ppm diminished the plants parameters in 50% in maize and alfalfa, respectively. On the other hand, only high atrazine concentrations, approximately 25 ppm with alfalfa and 50-75 ppm with maize, produced a 50 % reduction in the evaluated parameters. Knowing the herbicides concentrations that the plants can tolerate is a necessary step for developing phytoremediation strategies based on the eco-engineering of the rhizosphere environment.