Ammonium under solution culture alleviates aluminum toxicity in rice and reduces aluminum accumulation in roots compared with nitrate

• Published in: Plant and soil Vol. 315; no. 1-2; pp. 107 - 121
• Main Authors: Zhao, Xue Qiang, Shen, Ren Fang, Sun, Qing Bin
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.02.2009; Springer; Springer Netherlands; Springer Nature B.V
• Subjects: Acid soils; Agricultural soils; Agronomy. Soil science and plant productions; Al accumulation; Al toxicity; Aluminum; Ammonia; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Ecology; Fundamental and applied biological sciences. Psychology; Life Sciences; NH; Nitrates; NO; Nutrient solutions; Plant Physiology; Plant roots; Plant Sciences; Plants; Regular Article; Rice; Root tips; Seedlings; Soil Science & Conservation; Soils; Toxicity; NO; NH; Al accumulation; Al toxicity; Rice; Al toxicity NH4; Soil plant relation; NO3- . Rice
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-008-9736-8

Al stress and ammonium-nitrogen nutrition often coexist in acidic soils due to their low pH and weak nitrification ability. Rice is the most Al-resistant species among small grain cereal crops and prefers NH₄ ⁺ as its major inorganic nitrogen source. This study investigates the effects of NH₄ ⁺ and NO₃ ⁻ on Al toxicity and Al accumulation in rice, and thereby associates rice Al resistance with its NH₄ ⁺ preference. Two rice subspecies, indica cv. Yangdao6 and japonica cv. Wuyunjing7, were used in this study. After treatment with or without Al under conditions of varying NH₄ ⁺ and NO₃ ⁻ supply, rice seedlings were harvested for the determination of root elongation, callose content, biomass, Al concentration and medium pH. The results indicated that Wuyunjing7 was more Al-resistant and NH₄ ⁺-preferring than Yangdao6. NH₄ ⁺ alleviated Al toxicity in two cultivars compared with NO₃ ⁻. Both NH₄ ⁺-Al supply and pretreatment with NH₄ ⁺ reduced Al accumulation in roots and root tips compared with NO₃ ⁻. NH₄ ⁺ decreased but NO₃ ⁻ increased the medium pH, and root tips accumulated more Al with a pH increase from 3.5 to 5.5. Increasing the NO₃ ⁻ concentration enhanced Al accumulation in root tips but increasing the NH₄ ⁺ concentration had the opposite effect. These results show NH₄ ⁺ alleviates Al toxicity for rice and reduces Al accumulation in roots compared with NO₃ ⁻, possibly through medium pH changes and ionic competitive effects. Making use of the protective effect of NH₄ ⁺, in which the Al resistance increases, is advised for acidic soils, and the hypothesis that rice Al resistance is associated with the preferred utilization of NH₄ ⁺ is suggested.