pH-adjustment alleviates NH4 +-induced toxicity in Arabidopsis thaliana

• Published in: Journal of plant nutrition 2024-11, Vol.47 (18), p.3051-3062
• Main Authors: M'rah, Sabah, Chalh, Abdellah, Bensalem, Nada, BenAbdallah, Saoussen, Ouerghi, Zeineb, Ghnaya, Tahar
• Format: Article
• Language: English
• Subjects: Acidification; Ammonium; Arabidopsis thaliana; biomass; Cultivation; Hydroponics; N-assimilation; N-source, pH; Nitrate reductase; Nitrates; Nitrite reductase; Nitrogen dioxide; Nutrient concentrations; pH effects; Plant growth; Plant layout; Reductases; Seedlings; Toxicity
• ISSN: 0190-4167; 1532-4087
• DOI: 10.1080/01904167.2024.2376235

This work was conducted to evaluate the effect of N source (NH 4 + /NO 3 - ) and the implication of NH4+-induced acidification on plant development in Arabidopsis thaliana. seedlings were hydroponically cultivated during 21 days under three ratios of NO 3 − /NH 4 + (mM); 2.5/0.0; 1.25/1.25, and 0.0/2.5. For each ratio, plants were cultivated under not controlled pH and adjusted pH at 6.2. Ammonium-fed plants (0.0/2.5) showed chlorosis if cultivated under uncontrolled pH. This symptom was associated with suppressions in plant growth, chlorophyll and iron contents as well as shoots hydration and nutrient concentration. Growth was limited with increasing NH 4 + medium-concentration. At pH 6.2, plants receiving only NH 4 + produced the same biomass as NO 3 -fed ones. The mineral disturbances in plants grown on strictly NH 4 + -medium (0.0/2.5) were alleviated under controlled pH. The activities of nitrate reductase (NR) and nitrite reductase (NIR) were lower in plants amended only with NH 4 + under uncontrolled pH. At adjusted pH, the NR activity was ameliorated but that of NIR was not ameliorated, suggesting hence that NR activity depended on medium pH but that of NIR was related only to the pool of NO 2 - . In conclusion, this work demonstrated that the adjustment of pH at 6.2 mitigated significantly the toxic effects of ammonium to A. thaliana.