Total glutathione concentrations (GSH plus GSSG)
in the oldest, middle, and youngest leaves of plants grown in the
presence or absence of SO42− at either high (7
mm) or low (0.25 mm)
NO3−. Plants were grown for 3 weeks on 1
mm SO42− and 7 mm
NO3− before transfer to the four different
treatments at d 0. Data are the means ± se of three
separate plant samples. The lsd (P < 0.05) for each
time point is shown by vertical bars. There was no significant
difference between treatments in the oldest leaves. Open symbols, minus
S; closed symbols, plus S; circles, high N; triangles, low N. DW, Dry
weight.