Adventitious root formation in flooded tomato plants: insights on auxin and ethylene interaction

Soil flooding, which results in a decline in the availability of oxygen for the submerged organs, negatively affects the growth and productivity of most crops. Although tomato (Solanum lycopersicum) is known for its sensitivity to waterlogging, its ability to produce adventitious roots (ARs) increases plant survival when oxygen decreases in the root zone. Ethylene entrapment by water may represent the first warning signal to the plant of waterlogging. Treatment with both the ethylene-biosynthesis inhibitor aminoethoxyvinylglycine (AVG) and 1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, resulted in a reduction of AR formation in waterlogged plants. Ethylene perceived by the Never Ripe receptor stimulated auxin transport. In a process requiring the Diageotropica gene, auxin accumulation in the stem triggers additional ethylene synthesis, which further stimulated a flux of auxin towards the flooded parts of the plant. Auxin accumulating in the base of the plant induces preformed root initials to grow. This response of tomato plants results in a new root system capable of replacing the original one when it has been damaged by submergence.