EFFECTS OF PENDIMETHALIN ON CERTAIN OXIDIZING AND HYDROLYTIC ENZYME ACTIVITY DURING GERMINATION AND SEEDLING DEVELOPMENT OF SOYBEAN (GLYCINE MAX LIN. MERRIL.)N. RAJASHEKAR AND T. C. SIIIVASHANKARA MURTHI
Soybean seeds (Glycine max L. Merr.) were germinated in Hoagland and Arnon's nutrient media supplemented with a range of field relevant concentrations (0.5, 1.0, 2.5, 5.0, 10.0ppm) of formulated grade of pendimethalin. Shoot-root axis and cotyledon of 4, 6, 8, 10 and 15D old germinated soybean seedlings were used for bioassay to demonstrate the toxic effects of pendimethalin on the growth and activity of certain enzymes, during germination and early growth. Germination percentage, length of radicle and plumule was decreased drastically with increase in concentration of herbicide pendimethalin. A decrease in amylase activity in germinating seeds under control was marked with a comparative inhibition of amylase activity in seeds under pendimethalin stress in all days of observation. In treated seedlings polyphenoloxidase activity was high in both cotyledons and embryonic axis at all time intervals of seedlings during early growth over a period of 15 days. Increased activity of peroxidase and catalase was observed in embryonic axis at lower concentration (0.5 and 1 .Oppm) of pendimethalin treatment in all days of observations. Similarly peroxidase and ca ta lase activity was increased at 0.5, 1.0ppm and 0.5ppm concentrations respectively in cutyledon. However catalase and peroxidase activity was decreased and polyphenoloxidase activity was higher in treated seedlings at higher pendimethalin concentration. The present study with whole plant system clearly indicates that pendimethalin enhance abiotic stress resulting in lowered amylase activity and higher catalase, peroxidase and polyphenoloxidase activity..
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