UPTAKE OF C-14-SAN-789-F AND C-14-CYPROCONAZOLE INTO GERMINATING WHEAT FOLLOWING SEED TREATMENT AT DIFFERENT SOIL MATRIC POTENTIALS

The effects of fungicide uptake into germinating wheat and adsorption to the soil were studied following seed treatment with C-14-SAN 789 F, a fungicide of the homopropargylamine class, and C-14-cyproconazole, a triazole fungicide, at soil matric potentials between -2 and -70 kPa . Seed treatment with the strongly lipophilic SAN 789 F provided highl y-concentrated seed dressing zones over the whole range of soil matric potentials. As a consequence. SAN 759 F was efficiently absorbed by s eedlings over 3 d (approximately 35% of the total recovered amount). O n the other hand, the moderately lipophilic cyproconazole provided mor e diffuse seed dressing zones at soil matric potentials of -2 and -10 kPa resulting in reduced uptake rates. At -70 kPa, however, cyproconaz ole produced similar seed dressing zones as SAN 789 F, but was absorbe d by the seedling more efficiently than SAN 789 F (approximately 50% a fter 3 d). Quantitative analyses of the amount of C-14-SAN 789 F and C -14-cyproconatole incorporated into different plant tissues revealed t hat both compounds accumulated mainly in the testa (approximately half of the amount), that the embryo and the pericarp accumulated consider able amounts (approximately 25% each). Only traces were found in the r adicle and endosperm. When seeds were treated with SAN 789 F, moderate phytotoxic effects were observed independent of the size of matric po tential. In contrast, seed treatment with high concentrations of cypro conazole resulted in moderate phytotoxic effects at matric potentials of -2 and -10 kPa and strong effects at -70 kPa. Thus, phytotoxic effe cts of these two fungicides are mainly caused by the rate of fungicide uptake into germinating seeds. Moreover, uptake of these fungicides d epends on both the soil matric potential and the size of seed dressing zones. (C) 1998 Elsevier Science Ltd. All rights reserved.