Biology Reference
In-Depth Information
Statistical Analysis
To determine seed area and height, digital images of seeds on a white background
were thresholded in Adobe Photoshop CS2. These black and white images were
analyzed by ImageJ. We set a threshold on the grayscale such that the seed ap-
pears uniformly black against a white background. The black areas are detect-
ed automatically and converted as ellipsoids with the measurement of area and
minor axes. To test the differences between the means of two seed populations,
both analysis of variation (ANOVA) and the non-parametric Mann-Whitney test
(M-W) were employed as certain portions of very small seeds in some experiments
may have violated the normality assumption in ANOVA. 1:1 ratios of small and
large seeds were tested by the Pearson's
χ
2
test (
χ
2
). Finally, we used the Kalmago-
rov-Smirnoff Normality test (K-S) to determine whether seed size phenotypes fit
a normal distribution based on comparison to a generated ideal normal distribu-
tion of similar mean and standard deviation. Calculations were performed using
StatView 5.0.1 (SAS Institute, Cary NC), except for
χ
2
, which was calculated on
Excel×(Microsoft). p-values provided in the text are followed by the abbreviation
of the test used.
Authors' Contributions
Conceived and designed the experiments: FB AC JF. Performed the experiments:
FB JF ML. Analyzed the data: FB AC JF ML. Wrote the paper: FB JF.
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