Ammonium/nitrate ratio affects the growth and glucosinolates content of pakchoi

Abstract

Nitrogen (N) strongly affects plant growth. However, little is known about the effects of the ammonium/nitrate ratio on pakchoi (Brassica rapa), especially its glucosinolates (GSs) contents which are involved in plant defense and many of them benefit to human health. The aim of this study was to evaluate the effects of a constant N supply (8 mM) but with five ammonium/nitrate ratios (namely 0/8 mM, 2/6 mM, 4/4 mM, 6/2 mM and 8/0 mM) on the growth of pakchoi in a hydroponic system in 2 years. In both years, a higher biomass (dry weight) was in the 4/4 and 2/6 ammonium/nitrate treatments (2.3 and 2.2-fold compared to 8/0, respectively), with no significant difference in biomass between these two treatments. The biomass then decreased with increasing proportions of ammonium in the N supply from more than 10 g/pot to below 5 g/pot. The N and sulfur contents were strongly affected in the sole nitrate or ammonium treatments, as were the contents of chlorophyll, lutein, and β-carotene. Most of the individual glucosinolates (GSs) detected in pakchoi showed the highest concentrations in the sole ammonium treatment. The ammonium/nitrate ratio also affected the types of GSs. The highest proportion of indolyl GSs and the lowest proportion of aromatic GSs were in the sole ammonium treatment. We concluded that a high ammonium level decreases the biomass but increases the GSs concentrations in pakchoi. Further studies are required to explore the difference in GSs metabolism among plants supplied with different ammonium/nitrate ratios.

Optimal Dietary Crude Protein in Commercial Feeds for Shrimp and Halophytes in Marine Aquaponic Biofloc Systems

“…+ and NO 3 − , while the optimal ratio varies from species to species, common ratio of NH 4 + : NO 3 − are 1:9, 1:3, or 1:1 (Hawkesford et al, 2011;Zhang et al, 2019;Yang et al, 2020;Zhu et al, 2021). At the early stage of the present study, the concentration of NO 3 − (>10 ppm) was relatively higher than that of TAN (<0.5 ppm) and was the main source of N for plants in the water.…”

Differential Metabolic Responses of Lettuce Grown in Soil, Substrate and Hydroponic Cultivation Systems under NH4+/NO3− Application

“…The increase in flavonoids under different N fertilization treatments might be attributed to an increase in phenylalanine availability due to the restriction of protein synthesis under N deficiency. The phenylalanine availability could be substantially enhanced the production of secondary metabolites (polyphenols) as phenylalanine has been reported as a precursor for the formation of flavonoids in plants [ 92 , 93 ].…”

Mentha spicata L. grown with nitrate: Ammonium proportions in different light environments

“…It is pointed out that the increase in chlorophyll is due to the greater uptake and incorporation of N in the nitrate form, and thus it is inferred that the supply of N in the ammonium form may have impaired the assimilation of this nutrient thus decreasing the chlorophyll content. Contradictory results were found by Yang et al (2020), where these authors observed that CLA contents and CLA/B ratio were higher at the 75:25 NH 4). It is noteworthy that plants grown in a black mesh environment, at a 75:25 NO 3 -:NH 4 + ratio, showed higher LDM production, obtaining a higher percentage of 13.97 and 29.30% compared to the yield of those grown in full sun and under red mesh respectively, both grown at 100:0 NO 3 -:NH 4 + concentration (Table 4).…”