Role of auxin in induction of polarity in zygotes of Fucus vesiculosus L

We studied the effects of auxin (indolyl-3 acetic acid) on formation of the primary polarity axis in zygotes of the brown algae Fucus vesiculosus. Within the first 2.5 h after fertilization, the zygotes release this phytohormone in the environment. The treatment of developing zygotes with the inhibitor of indolyl-3-acetic acid transport from the cell triiodobenzoic acid at 5 mg/l arrests the auxin secretion and leads to its accumulation in the cells. This causes a significant delay in zygote polarization. The treatment of zygotes with the exogenous indolyl-3-acetic acid at 1 mg/l stimulates cell polarization and formation of a rhizoid process. When auxin was added to the medium with triiodobenzoic acid, the inhibitory effect of the latter was fully relieved. It has been proposed that the content of indolyl-3-acetic acid in the environment is a key factor in the induction of polarity of the F. vesiculosus zygotes.