Figure 6.

AR emergence and the growth angle of ARs are controlled by red and far-red light signaling. A, Stem sections including the third node show a fluence rate-dependent change in growth angle when exposed to far-red light. For comparison, a stem is shown that was exposed for 3 d to white light in the presence of 150 μm ethephon (WL+E). Ethephon releases ethylene that promotes AR growth even in the light. B, Percentage of ARs that penetrated at the third node in darkness (0), red light (R), far-red light (FR), or white light (WL) after 3 d. The inset shows a higher resolution of the low fluence range. C, Angle of ARs at the third node of stems exposed as described in A. The inset shows a higher resolution of the low fluence range. In B and C, results are means ± se from four independent experiments, with 18 to 30 stems analyzed per treatment. Different letters indicate statistically significant differences (P < 0.05, ANOVA with Tukey’s test).