Abscisic acid inhibits germination and indirectly delays ethylene biosynthesis of Beta vulgaris

Ethylene and abscisic acid (ABA) are known to interact during the germination of several species. However, ethylene is not involved during the germination of Beta vulgaris, questioning a possible interaction with ABA. Our results have shown that ABA delays the germination of B. vulgaris in a concentration-dependent manner. By analysing the ethylene biosynthesis pathway, the ethylene release rate was shown to be delayed when ABA is supplemented, most probably due to the slower germination rate. The inverse interaction in which 1-aminocyclopropane-1-carboxylic acid (ACC) affects ABA levels does not seem to occur in B. vulgaris as no changes in ABA content were observed during germination in the presence of ACC at different concentrations. Levels of certain plant growth regulators (ABA, ACC and auxin) were also shown to be much higher in the fruit pericarp compared with the true seed. Presumably the pericarp plays an important role during the germination process of B. vulgaris because it is a physiochemical boundary with drastic differences in hormone levels. Our results clearly show demonstrate that ethylene is not involved during the actual germination of B. vulgaris, and that there is no effect of ethylene on ABA during germination of B. vulgaris.