Effect of Pb-stress on selected physicochemical surface properties of barley (Hordeum vulgare L.) roots
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Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland
Department of Ecology and Biology, Lviv State Agrarian University, Dublyany, V. Velukogo 1, Ukraine
Int. Agrophys. 2007, 21(4): 399–403
The objective of this research was to study the roots spring barley of the Ukrainian Peyas variety. The plants grew in a nutrient solution at pH 7, with a 16/8 h (day/night) diurnal light cycle and at temperatures of 20/16°C (day/night). At the beginning of the tillering stage, Pb(NO3)2 was introduced in to the nutrient medium in the amount of 320 mg per 1 dm3 of the solution and the pH of the containers with Pb+2 was lowered to 4.5. The control setup consisted of containers free of Pb+2 ions at pH 7 and 4.5. Plants were grown for 10 days. Next, all the plants were collected and the surface charge of the roots was determined by the titration method. The titration was performed using the Titrino 702 MS titrator (Mertohem Ion analysis – Metrohem Ltd., CH-9101 Herisau, Switzerland) apparatus and 0.1 M solution of NaOH in 1 M NaCl as the titrate. Under the influence of Pb+2 ions, the total variable charge (Q) and cation exchange capacity (CEC) of roots increased. However, the total acidity of the root surface did not exhibit changes. Also, no significant differences were observed between roots growing without Pb+2 ions at pH 7 and pH 4.5. In addition to titration, water vapour isotherms were measured for the roots of the plants. From the isotherms, the apparent surface area was calculated using BET theory. Under Pb+2 stress the apparent surface area of the roots decreased.