Figure 4: Auxin treatment with low doses stimulates seed germination and enhances DNA content.

(a,b) Germinating seeds of Col (left) are shown after 36 h imbibition in 5 nM IAA or mock solution (a) and 48 h imbibition in 0.05 nM 2,4-D or mock solution (b). The graphs on the right show seed germination percentages during imbibition with different concentrations of (a) IAA and (b) 2,4-D (0.05–5 nM) treatment. Different letters at the same timepoint indicate a significant difference determined by Tukey’s honestly significant difference (HSD) test (P<0.05). Scale bars, 1 mm. (c) Changes in nuclear ploidy levels during seed imbibition. Histograms representing DNA content of embryo cells during seed imbibition (left). Fully after-ripened wild-type Col seeds were imbibed for 24 h (upper panel) or 36 h (lower panel) in a mock solution, 5 nM IAA or 0.05 nM 2,4-D. 2C peak, G1 DNA content; 4C peak, G2 DNA content; 8C and 16C peaks, endoreduplicating cells. The graphs in the right show a quantification of the cell numbers at the different stages of the cell cycle based on the histograms. The bars indicate s.d. of three biological replicates and different letters indicate a significant difference determined by Tukey’s HSD test (P<0.05).