Metabolomics Analysis Reveals Potential Mechanisms in Bupleurum L. (Apiaceae) Induced by Three Levels of Nitrogen Fertilization

Bupleurum (Apiaceae) is widely used in traditional Chinese medicine to treat inflammatory and infectious diseases. Although roots are the only used parts in China, other countries use the whole plant. The yield and quality of Bupleurum depend mainly on fertilizers, especially nitrogen. The current study aimed to assess the relationship between the nitrogen fertilization level and the quality and metabolomic response of different parts (flowers, main shoots, lateral shoots and roots) of Bupleurum to three nitrogen fertilization levels (control group: 0 kg·ha−1; low-nitrogen group: 55 kg·ha−1; high-nitrogen group: 110 kg·ha−1). The results showed that a high nitrogen level increases Bupleurum yield and quality parameters only in aerial parts, especially flowers, but has no significant effect on roots. The HPLC method was exploited for simultaneous quantification of three saikosaponins (A, C and D), which are the main bioactive components in the plant. It was found that the total content of saikosaponins decreased with high nitrogen fertilization in roots but significantly increased in flowers. Moreover, nitrogen fertilizer promoted the content of saikosaponin A but inhibited saikosaponins C and saikosaponins D in most parts of the plant. To study the response of primary metabolites, we adopted gas chromatography–mass spectrometry (GC−MS) analysis; 84 metabolites were identified that were mostly up-regulated with a high nitrogen level in flowers but down-regulated in roots. Four differential metabolites—D-fructose, lactose, ether and glycerol—were recognized as key metabolites in Bupleurum under nitrogen fertilization. Meanwhile, The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment results explained that the impact of nitrogen fertilization on Bupleurum was attributed to the C-metabolism, N-metabolism, and lipids metabolism. This research put forward new insights into potential mechanisms and the relationship between the quality and yield of Bupleurum and nitrogen fertilization.

Effects of nitrogen application on phytochemical component levels and anticancer and antioxidant activities of Allium fistulosum

Background Allium fistulosum L. has good nutritional value and is cultivated worldwide as an efficacious traditional medicinal plant. Its biological activities are attributable to its phytochemicals. Nitrogen is an essential nutrient for plant growth and development; however, the effect of nitrogen levels on the level of active components in this species is not well understood. Methods In this study, using urea fertilizer, we investigated the effects of different nitrogen levels (N0, N1, and N2 at 0, 130, and 260 kg/ha, respectively) on the phytochemical constituents , and antioxidant and anticancer properties of A. fistulosum. Results The results suggested that nitrogen fertilizers have a significant effect on the level of total phenols and flavonoids. The analysis of the antioxidant capacity revealed that the lowest IC50 values corresponded to plants treated with the highest nitrogen concentration. Anticancer activity was investigated against cancer cell lines (HeLa and HepG2), and the extracts of A. fistulosum treated with a high nitrogen level showed the highest antiproliferative effect. Collectively, our results suggest that nitrogen fertilizer application enhanced the quality of A. fistulosum, particularly its health benefits.

Facile synthesis of nitrogen-doped unzipped carbon nanotubes and their electrochemical properties

N-UCNTs with a high nitrogen level, large surface areas and good crystallinity are synthesized by pyrolysis of an O-UCNTs/melamine composite.

Influence of nitrogen supply on spring barley productivity and nitrate reductase activity

The aim of the present study was to obtain some informations on the productivity of four chosen barley varieties growing at low and high nitrogen level. Some parameters of the yield structure and nitrate reductase activity were taken into consideration. It was found that there exist some differences in the yield between the compared varieties and some differences in their reaction to a high N level in the soil. The grain yield increase of the plants treated with high nitrogen doses was above all the result of the increase in dry matter of the lateral shoots and in leaf area. Distinct increase in the number of grains per ear and 1000-grains weight was also observed. The amount of reduced nitrogen collected during the growth season depended, in part, on the nitrate reductase activity and in part on the amount of the enzyme present in the plant. A rise of the nitrogen level caused an increase in nitrate reductase activity, in all varieties. The different influence of nitrogen on the growth of green organs in the compared varieties caused differences in the amount of the enzyme present in the plants and in protein yields.

Low-temperature induced floret sterility in the rice cultivars Calrose and Inga as influenced by nitrogen supply

An experiment in temperature-controlled glasshouse chambers at Yanco Agricultural Institute examined floret sterility in lnga and Calrose rice induced by low temperature and high nitrogen level. Low temperature (12�C) ,for 4 d during microsporogenesis and anthesis produced considerable sterility in both cultivars; lnga was more sensitive than Calrose. Sensitivity was greatest when florets from the mid-section of the panicle were passing through the early microspore phase of pollen development. At both stages, the amount of low-temperature induced sterility was increased by high nitrogen supply. In the absence of low temperature, high nitrogen levels induced sterility in lnga only.

Effect of ammonium on growth of plant cells (Ipomoea sp.) in suspension cultures

Maintenance of the ammonium level in batch cultures of a plant cell line initiated from Ipomoea root tissue resulted in cells with a higher nitrogen content and a greater total accumulation of nitrogen in the cells. Utilization of nitrate was not suppressed. The increased supply of ammonium did not, by itself, increase the yield of dry cells, but it did permit a twofold or greater increase in cell yield when sucrose was added subsequently.Supplementary feeding of ammonium and sucrose to a batch culture that had exhausted the initial supply of ammonium rapidly returned the cells to a state of high nitrogen content, favored further utilization of nitrate, and greatly increased cell yield.These results are discussed in terms of growth phases. The presence of ammonium in the medium appeared to induce and maintain a growth phase characterized by a high nitrogen level in the cells. After the ammonium supply was depleted a second phase occurred, characterized by a rapid increase in dry weight without proportional accumulation of nitrogen. This second phase was not caused by a limiting rate of nitrate utilization, nor was it directly related to observed pH changes. We conclude that the two phases relate to the presence and absence of ammonium in the medium.

Apical dominance in the rhizome of Agropyron repens. Some factors affecting the degree of dominance in isolated rhizomes

A study of apical dominance in isolated rhizomes of Agropyron repens L. Beauv. showed that increasing the length of the rhizome significantly reduced the degree of dominance only in rhizomes from plants grown at a high nitrogen level (210 ppm). Exposing the rhizomes to light also reduced dominance more effectively in high-nitrogen rhizomes but the response of rhizomes from low-nitrogen plants was greatly increased by supplying water through the end of the rhizome. Further experiments with low-nitrogen rhizomes showed that buds could be released from apical dominance by treatment with kinetin. When isolated from the plant the buds showed a significant increase in length after 24 h and an associated increase in moisture and insoluble nitrogen content. Soluble nitrogen and carbohydrate increased concurrently during the next 24 h. Rhizomes kept in darkness showed a small reduction of bud inhibition when water was supplied through the cut end; NH4NO3 solution had a greater effect, while solutions in which both nitrogen and carbohydrate (as sucrose) were supplied resulted in the almost complete elimination of apical dominance.The results suggest that apical dominance in isolated, low-nitrogen rhizomes was due mainly to competition between the apex and the lateral buds for water, nitrogen, and carbohydrate.