Figure 4.

Endogenous GA levels in potato wild-type and transgenic plants overexpressing either GA20ox or GA2ox. GAs were isolated from the shoot apex of growing plants (leaf nos. 1–5) and analyzed using gas chromatography-mass spectrometry. Values are shown as ng GA g⁻¹ dry weight and represent means ± sd of three to five independent experiments. * Statistically significant differences from the wild type were determined in one-tailed t tests assuming unequal variance (P ≤ 0.05). The inset shows a schematic drawing of the changes in GA metabolism due to the expression of GA2ox (black circles) or GA20ox (gray circles) in potato plants. GA₁₂ is the common precursor for all GAs. The 13-hydroxylation pathway leads to GA₁, whereas the 13-nonhydroxylation pathway leads to GA₄, as major bioactive forms. Bioactive GA species are underlined.