Arbuscular mycorrhizae alleviate water deficit stress and improve antioxidant response, more than nitrogen fixing bacteria or chemical fertilizer in the evening primrose

Abstract

We treated the evening primrose grown under moderate or severe water deficit with an arbuscular mycorrhizal fungus (Glomus mosseae), and nitrogen fixing bacteria (Azospirillum lipoferum), or with a chemical fertilizer (urea + triple superphosphate). The experiment was conducted at an arid and a semi-arid experimental station with plants grown in the field, after greenhouse propagation. Experiments were conducted in a split factorial layout within a randomized complete block design with three replications, at each location. Our results show that under physiological stress conditions caused by water deficit, the evening primrose adopts typical strategies to reduce the negative impact of water deficit stress. Some of these strategies include antioxidant enzyme synthesis, which protect from reactive oxygen species, a decrease in overall growth, but relative increase in root, and an increase in plant antioxidant pigments. Water deficit significantly reduced plant total biomass and chlorophyll a (especially in the arid region), but it increased the root to shoot ratio, chlorophyll b, carotenoid, anthocyanin, proline, the antioxidant enzymes peroxidase, polyphenol oxidase, superoxide dismutase, malondialdehyde and hydrogen peroxide (especially in the arid region). The application of the chemical fertilizers and biological inoculants in all conditions decreased H2O2 and antioxidant enzymes activity. The arbuscular mycorrhizae alleviated the physiological stress response more than the nitrogen fixing bacteria or chemical fertilizer by increasing anti-oxidant pigments concentration, total biomass and root to shoot ratio of evening primrose under water deficit stress. Therefore, arbuscular mycorrhizae should be considered an essential component of evening primrose cultivation in arid or semi-arid climates to alleviate moderate to severe water deficit.