Ammonium sulphate induces dose-dependent ammonium stress in rice seedlings

Abstract

Plants require nitrogen (N) in various forms to facilitate essential physiological functions. Nitrate (NO3-) is one of the most readily absorbed N forms by plants and is preferred in well-aerated soils because it can be easily transported within the plant. Ammonium (NH4+), on the other hand, is utilized especially in waterlogged or acidic soils, where it is directly absorbed by the roots and incorporated into amino acids. Urea (CH4N2O) is another significant N source found in many fertilizers; it is transformed into NH4+ and nitrate in the soil through microbial processes. These diverse forms of N are crucial for supporting photosynthesis, protein synthesis, and energy production in plants. The escalating use of ammonium sulphate (NH4)2SO4) as a N source in agriculture prompts a thorough examination of its impact on crop health and productivity. This study aimed to investigate the NH4+ toxicity on rice (Oryza sativa) plants by administering various dosages (0 mM, 5 mM, 7 mM, 10 mM, 12 mM, and 15 mM) and assessing their effects on plant growth parameters, particularly root-shoot lengths, root-shoot fresh biomass along with dry weight. Our research utilized a controlled experimental setup to monitor the growth responses of rice plants to these NH4+ concentrations. Results indicated a clear threshold of tolerance, with adverse effects becoming significant at concentrations starting from 7 mM. At this concentration and higher, there was a noticeable decline in root-shoot lengths, root-shoot biomass and dry biomass, marking the onset of toxicity symptoms in rice plants. These findings suggest a critical need for regulated application of (NH4)2SO4 in rice cultivation to avoid detrimental effects on plant health and yield. The study underscores the importance of establishing safe usage guidelines for (NH4)2SO4 in agriculture, ensuring sustainable farming practices while maintaining crop productivity.