Statistical analysis
Statistical analyses were conducted using SAS statistical software (SAS
Institute 9.0 Inc., 2002). All measured and calculated traits were used
for analysis (Table 2). To minimize variance heterogeneity, all data
were log-transformed, except for petiole angles and branch angles
(square root-transformed), before statistical analysis. For plant total
mass, we applied two-way ANOVA to analyze effects of germination timing,
sampling time and their interactions, and one-way ANOVA to analyze the
effects of germination timing or sampling time within each or across all
of the other treatments. Plant size (e. g. total mass) can have very
significant effects on other traits, which may bias the effects of
germination time. Therefore, for all the other traits, we applied
two-way ANCOVA to evaluate overall effects of germination timing,
sampling time and their interactions, and one-way ANCOVAs for effects of
germination timing or sampling time within each or across all of the
other treatments, with total mass as a covariate. For a given trait,
significant contribution of total biomass (plant size) to its variation
in response to germination timing indicates an occurrence of apparent
plasticity (McConnaughay & Coleman, 1999). When effects of total mass
were removed, the variation due to germination timing in trait
expression was an indication of true plasticity (Weiner, 2004). Multiple
comparisons used the Least Significant Difference (LSD) method in the
General Linear Model (GLM) program, which produced adjusted mean values
and standard errors in one-way ANCOVA.