Figure 7.

The effects of indole-3-actic acid (IAA), the auxin transport inhibitor TIBA, and other auxin-related inhibitors on Lepidium sativum seed germination and its inhibition by myrigalone A (MyA). (A) The effect of adding a low IAA concentration on the kinetics of testa rupture (TR) and subsequent endosperm rupture (ER) without (Con, control) or with 0.5 mM MyA added. Note that combined treatment with a low IAA concentration partly reverts the MyA-mediated delay of ER. (B) The effect of adding a low IAA concentration on the kinetics of TR and ER without (Con) or with 100 µM TIBA (2,3,5-triiodobenzoic acid) added. Note that combined treatment with a low IAA concentration fully reverts the TIBA-mediated delay of ER. (C) IAA dose-response of cress seed germination for the low concentration range. (D) The effects of IAA and gibberellin (100 µM GA₄₊₇) on germination. (E) The effect of adding a high IAA concentration on the kinetics of TR and ER without (Con) or with 100 µM TIBA added. Note that combined treatment with a high IAA and TIBA resulted in additive ER inhibition. (F) IAA dose-response of cress seed germination for the high concentration range. (G) The effect of the TIR1 auxin receptor antagonist auxinole (100 µM) and of the auxin biosynthesis inhibitors (100 µM) aminoethoxy-vinylglycine (AVG) and L-kynurenine on cress seed germination. (H) The effects of TIBA and gibberellin (100 µM GA₄₊₇) on germination. (I) TIBA dose-response of cress seed germination. Note that TIBA inhibits ER in a dose-dependent manner without affecting TR. Seeds were incubated at 20 °C in continuous white light, TR and ER scored over time, mean values ± SEM for 3 replicates each with ca. 30 seeds are shown.