. The Canadian field-naturalist. 1998 Notes 537 beneath the Kaladar tower increased due to corrosion of the protective Zn coating on the tower, selection may have given rise a population of D. flexuosa tol- erant to Zn. This note reports the results of a hydro- ponic test for tolerance to Zn by roots of tillers of D. flexuosa collected under and around the same Kaladar tower. Materials and Methods The transmission tower is located on the south side of the Trans Canada Highway, near Kaladar, Ontario, Canada at 44° 33'N, 77° 15'W. Small tufts (30), of D. flexuosa, each consisting of several till
. The Canadian field-naturalist. 1998 Notes 537 beneath the Kaladar tower increased due to corrosion of the protective Zn coating on the tower, selection may have given rise a population of D. flexuosa tol- erant to Zn. This note reports the results of a hydro- ponic test for tolerance to Zn by roots of tillers of D. flexuosa collected under and around the same Kaladar tower. Materials and Methods The transmission tower is located on the south side of the Trans Canada Highway, near Kaladar, Ontario, Canada at 44° 33'N, 77° 15'W. Small tufts (30), of D. flexuosa, each consisting of several tillers, were collected randomly under the tower and within 5 m of the tower in small channels which car- ried run-off from the corroding lattice structure. A further 30 tufts were collected 60 m south-west of the tower, in the up-wind direction of the generally prevailing wind. At such a distance it is unlikely that the soil is being contaminated with Zn from the tower. Soil was shaken from the roots of the tufts for later analysis and individual tufts were rinsed thor- oughly with tap water. The tufts were placed in quarter-strength Hoagland's solution (Hoagland and Arnon 1950) for two months of growth. Then healthy individual tillers were removed from respec- tive tufts for the hydroponic culture root-growth tol- erance test described in Al-Hiyaly et al. (1988). Tillers, replicated two to four times, depending on the size of the tufts from which they were collected, were selected to determine root growth in quarter- strength Hoagland's solution (Hoagland and Arnon 1950) containing Zn (as zinc sulphate) selected from the following range of concentrations, 0, , or |ig Zn 1"', giving solutions of pH , , and , respectively). The roots of each tiller, clipped to 4-cm length, were inserted into a 5-cm long plastic drinking straw for support. Individual straws were inserted in Styrofoam sheet (6 cm X 6 cm and 2 cm thick) so that the roots were immersed in
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