Results were analysed by split-plot analysis of variance using
Genstat 5 Release 6.1 (Rothamsted Research, Harpenden, Herts,
UK). The main effects of species were tested against between-plot
variation, while the influence of leaf age and soil water status and
their interaction with species were tested against within-plot
variation, producing two standard errors of the difference (SED),
one for comparing means between species and the other for
comparing means within species. Inspection of residual plots to
test for normality and homogeneity showed there was no need to
transform data before analysis. Rectangular hyperbolae were fitted
to the PPFD response curves for net assimilation rate (A) by nonlinear
regression; one curve was fitted to the data for all species
before fitting separate curves for each species to test the
improvement in significance of fit.
Results were analysed by split-plot analysis of variance usingGenstat 5 Release 6.1 (Rothamsted Research, Harpenden, Herts,UK). The main effects of species were tested against between-plotvariation, while the influence of leaf age and soil water status andtheir interaction with species were tested against within-plotvariation, producing two standard errors of the difference (SED),one for comparing means between species and the other forcomparing means within species. Inspection of residual plots totest for normality and homogeneity showed there was no need totransform data before analysis. Rectangular hyperbolae were fittedto the PPFD response curves for net assimilation rate (A) by nonlinearregression; one curve was fitted to the data for all speciesbefore fitting separate curves for each species to test theimprovement in significance of fit.
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