Physiological role of silicon in radish seedlings under ammonium toxicity

Abstract

BACKGROUND: High concentrations of ammonium as the sole nitrogen source may result in physiological and nutritional disorders that can lead to reduced plant growth and toxicity. In this study, we hypothesized that ammonium toxicity in radish seedlings (Raphanus sativus L.) might be mitigated by the incorporation of silicon (Si) into applied nutrient solution. To examine this possibility, we conducted a hydroponic experiment to evaluate the effects of five concentrations of ammonium (1, 7.5, 15, 22.5, and 30 mmol L −1) on the photosynthesis, green color index, stomatal conductance, transpiration, instantaneous wateruse efficiency, and biomass production of radish in the absence and presence (2 mmol L −1) of Si. The experimental design was a randomized block design based on a 2 × 5 factorial scheme with four replicates. RESULTS: The highest concentration of applied ammonium (30 mmol L −1) was found to reduce the photosynthesis, transpiration and total dry biomass of radish seedlings, independent of the presence of Si in the nutrient solution. However, at lower ammonium concentrations, the application of Si counteracted these detrimental effects, and facilitated the production of seedlings with increased photosynthesis, greater instantaneous water-use efficiency, and higher total dry biomass compared with the untreated plants (without Si). Transpiration and stomatal conductance were affected to lesser extents by the presence of Si. CONCLUSION: These findings indicate that the addition of Si to nutrient solutions could provide an effective means of alleviating the unfavorable effects induced by ammonium toxicity at concentrations of less than 30 mmol L −1 .

Water stress and warming impact nutrient use efficiency of Mombasa grass (Megathyrsus maximus) in tropical conditions

“…Aboveground biomass production was estimated using a quadrat of 0.2 m × 0.2 m (area of 0.04 m 2 ). We collected three samples per plot, washed with neutral detergent solution (0.2%) and HCl solution (0.1%), and deionized water (Olivera‐Viciedo et al., 2020). Samples were packed in paper bags and dried in a stove at 60°C until constant weight and powdered in an electric mill (Willey type).…”

“…N was determined from the digestion in sulphuric acid, using the Kjeldahl procedure of Bataglia, Furlani, Teixeira, Furlam and Gallo (1983). From the digestion of the samples in diacid mixture of nitric acid (HNO 3 ) and perchloric acid (HClO 4 ), P concentration was determined in a spectrophotometer from the phospho‐vanado‐molybdic complex formed in the reaction of P with the solution of molybdovanadate, while K, Ca, Mg and micronutrients were determined by atomic absorption spectrometry, according to the protocol of Bataglia, Furlani, Teixeira, Furlam, and Gallo (1983). According to the nutrient concentration and dry mass of plants (kg/ha), we calculated the aboveground accumulation of each macronutrient (kg/ha) and micronutrient (g/ha), respectively.…”

The role of silicon on C:N:P stoichiometry and yield of sugar beet under ammonium toxicity

“…Nitrogen (N) availability is one of the most important factors that determine plant growth in a wide range of environments 1,2 . Ammonium (NH 4 + ) and nitrate (NO 3 − ) are the main forms of N absorbed by plants 3 .…”

“…Thus, urea, the worldwide leading nitrogen-fertilizer is converted to ammonium by urease enzymes of soil microorganisms and plants 4 . Consequently, the lower metabolic energy expenditure associated with ammoniacal nutrition can be converted into higher plant growth, and thus higher production 1,5 .…”

“…Despite its value as a fertilizer, it is well established that an excess of NH 4 + can promote the production of reactive oxygen species (ROS), which can cause reductions in cytoplasmic pH, photosynthetic rate, transpiration, and stomatal conductance 1 . Depending on concentration, the exclusive supply of N as NH 4 + is harmful to many plants and may cause poor biomass accumulation and ion imbalance 1,5,6 .…”