Effects of humic acid-herbicide interactions on the growth of Pisum sativum in nutrient solution
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- Senesi, N., Loffredo, E. & Padovano, G. Plant Soil (1990) 127: 41. doi:10.1007/BF00010835
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Slight increases in root length and dry matter production were measured in roots and shoots of Pisum sativum seedlings, when germinated seeds were grown for eight days in a controlled environment chamber, on Nitch nutrient solution to which 10 mg L-1 soil humic acid (HA) had been added. A concentration of 100 mg L-1 of HA produced a small reduction in dry matter production of shoots. In the presence of herbicides, 10 mg L-1 cycluron or 100 mg L-1 prometone, root elongation and shoot growth was reduced by varying degrees with respect to the control. Nutrient solutions containing 100 mg L-1 cycluron, 10 or 100 mg L-1 alachlor, or as little as 0.1 mg L-1 of 2,4-D resulted in an almost complete suppression of the growth of pea seedlings. The addition of 10 or 100 mg L-1 of HA to nutrient solution containing the herbicide was found to be either ineffective in enhancing growth, or even further reduced growth, compared to samples grown in the presence of the herbicide alone. The results of this preliminary study suggest that the generally accepted view that humic substances exert a positive effect on plant growth may not occur when humic substances interact with herbicides.