Table 3 Mean nitrogen concentrations (μmol g dw^-1 ± SE; N = 75) of roots, stems, leaves and cuttings of Populus balsamifera L. hydroponically grown with nitrate or ammonium

Root

2.50 ± 0.04

2.55 ± 0.03

Stem

0.41 ± 0.01

0.76 ± 0.03

Leaf

1.84 ± 0.03

2.19 ± 0.04

Cutting _start

0.83 ± 0.01

0.83 ± 0.02

Cutting _end

0.59 ± 0.03

0.71 ± 0.02