Environmental and Experimental Botany 51 (2004) 145–153 Boron and water uptake in jack pine (Pinus banksiana) seedlings Kent G. Apostol, Janusz J. Zwiazek ∗ Department of Renewable Resources, 4-42 Earth Sciences Building, University of Alberta, Edmonton, Canada T6G 2E3 Received 16 May 2003; received in revised form 2 September 2003; accepted 4 September 2003 Abstract We studied the effects of 0.5, 1 and 2mM boron (B) on growth, water and nutrient uptake in 6-month-old jack pine (Pinus banksiana) seedlings. After 6 weeks of treatment, B did not significantly affect survival and the measured growth parameters in jack pine. However, B-treated seedlings exhibited needle tip necrosis that progressed toward the bases of the needles in high concentration treatments. The visible needle injury was accompanied by an increase in electrolyte leakage from the needles and B accumulation in needles. The needles of plants treated with 2 mM B contained three-fold higher concentration of B than with the roots. In plants treated with B for four 10 and 6 weeks, stomatal conductance was reduced with a concomitant reduction in a steady-state root water flow. However, tissue concentrations of essential elements including K, P, Ca, Mg, and S were not altered by the B treatments. Therefore, water transport did not appear to affect uptake and distribution of mineral nutrients in jack pine and the observed needle necrosis and electrolyte leakage could be explained by B accumulation in the needles. Although photosynthetic pigments and the measured growth parameters were not altered by the 6-week B treatments, long-term growth effects should be anticipated due to effect of B on water relations. © 2003 Elsevier B.V. All rights reserved. Keywords: Boron toxicity; Electrolyte leakage; Needle necrosis; Root water flow; Stomatal conductance; Tissue elements 1. Introduction Boron, which is widely distributed in the litho- sphere and hydrosphere (Power and Woods, 1997), is an essential microelement in higher plants (Hu and Brown, 1997). Boron requirements vary among species from 5 to 15 ppm (Kozlowski and Pallardy, 1997). The optimum quantity for one species could ∗ Corresponding author. Tel.: +1-780-492-2358; fax: +1-780-492-1767. E-mail address: janusz.zwiazek@ualberta.ca (J.J. Zwiazek). be either toxic or insufficient for another species (Blevins and Lukaszewski, 1998). Boron is an impor- tant constituent of the cell walls and has been reported to be involved in enzyme activation, membrane main- tenance, nucleic acid metabolism and sugar translo- cation (Loomis and Durst, 1992; Power and Woods, 1997). Boron deficiency is commonly associated with acidic soils, and in sandy soils low in silt and clays (Stone, 1990). High concentrations of B are present in arid areas, and areas disturbed by surface mining, including oil sands in western Canada (Nable et al., 1997; Renault et al., 1998). 0098-8472/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2003.09.002