Comparison of the effects of nitrate and ammonium forms of nitrogen on auxin content in roots and the growth of plants under different temperature conditions

Average root length, root/shoot ratio and auxin content in roots were higher in plants supplied with nitrate rather than ammonium and grown at 18, 21, 24°C. The effects on root length were most pronounced at the highest temperatures (21 and 24°C); and the warmer the temperature, the earlier appearance of the differences in growth rate between NO3- and NH4-fed plants. A sharp acceleration of root growth was characteristic of NO3-fed plants grown at 21 and 24°C and was associated with a temporary increase in auxin concentration measured by immunoassay.