The effect of the signal molecule and stress phytohormone abscisic acid (ABA) on activities of antioxidant enzymes was tested in three bryophyte species, viz., the liverwort Marchantia polymorpha and the phylogenetically unrelated mosses Physcomitrella patens and Atrichum undulatum. Production of reactive oxygen species increases in plants exposed to both abiotic and biotic stress. Antioxidant enzymes are very effective and usually represent the plant's first line of defence against the cytotoxic effects of these reactive oxygen species. The activities of enzymes of the antioxidative system (POX, CAT, SOD) in the tested bryophyte species are shown to be increased by treatment with lower concentrations of exogenous ABA. Higher concentrations of exogenous ABA did not significantly influence activities of the tested antioxidative enzymes. The obtained results point to possible involvement of ABA as a signal molecule in the first line of defence against stress in all three bryophyte species.

Botanica Serbica (2017), 41(1): 11-15