The chemical composition of fulvic acid (FA) with a molecular weight below 500 (FA-500) was analyzed, and its activity on promoting the seed germination of wheat was studied in this paper. The FA-500 was obtained by membrane separation technology and qualitatively and quantitatively analyzed by using gas chromatography-mass spectrometry combined with the retention index. Forty-seven constituents were identified, including structures with ester, acid and alcohol groups, which accounted for 95% of the total composition. The highest relative content of compounds was diethyl succinate and diethyl malonate, accounting for 29% and 17% of the total, respectively. Yannong 19 and Luyuan 301 wheat seeds were steeped with the FA-500 solution of different concentration respectively for two hours. Several markers were assessed: germination rate, coleoptile and radicle length, germination index, vitality index and the activity of α-amylase and (α+β) amylase. The results indicated that FA-500 had a significant effect on promoting seed germination within an appropriate concentration range. The best concentration was 0.5‰, and an inhibiting effect would appear with the increase of concentration. In the process of seed germination, FA-500 may affect the growth of the seed through influencing the amylase activity, which was related to respiration.

Citrus limon (L.) Burm. f. is a horticultural crop known for its abundance of valuable secondary metabolites, including flavonoids, which are found in its fruits and leaves. Our previous research has shown that treating C. limon with fulvic acid (FA) can enhance the levels of vitamin C, total acid, total sugar, total flavonoids, and phenols in its fruits as well as the volatiles and total flavonoids in its leaves. In this current study, we established a method to analyze eight specific flavonoids in lemon leaves and evaluated the impact of irrigation with FA on the content of these flavonoids over a six-month period using HPLC-DAD/MS analysis. Moreover, we investigated the potential mechanisms of FA through ELISA and q-PCR methods. The results indicated that FA increased the contents of four flavonoids, namely, isoorientin, eriocitrin, vitexin, and rutin, and promoted the activity and gene expression of phenylalanineammonialyase (PAL), 4-coumaric acid coenzyme A ligase (4CL), chalcone synthase (CHS), flavonoid 3′-hydroxylase (F3′H), and flavonol synthase (FLS). Furthermore, the relationship between flavonoid content and the activities of biosynthetic enzymes was analyzed using orthogonal partial least squares discriminant analysis (OPLS-DA), which revealed a positive correlation between seven flavonoid levels and the activity of five biosynthetic enzymes under FA treatment.

The lignite upgrading wastewater (LUW) produced in the drying and upgrading process of lignite cannot be discharged directly. Conventional wastewater treatment methods are usually costly and unable to achieve efficient utilization of water resources which are rich in activity components. In this study, the water quality analysis showed that LUW belonged to seriously polluted waters with low pH and very high total nitrogen content. Fifty-five compounds, mainly phenols and organic acids, were identified by gas chromatography-mass spectrometry (GC-MS) analysis. The study confirmed that the LUW, after being diluted to an appropriate concentration, could significantly promote the growth of wheat seedlings. The phenols and organic acids were the activity material basis of LUW, which promoted seed germination possibly through playing a role similar to plant hormones and simultaneously enhancing the utilization of nutrient elements. LUW had the natural advantages of directly developing high-end liquid fertilizers in terms of its physical form, chemical composition, biological activity, safety and economy. This study confirmed the feasibility of applying LUW to agricultural field as liquid fertilizer only through simple dilution without other treatments. Applying LUW as liquid fertilizer can not only supply a fertilizer product with low production cost and outstanding efficacy, but also provide an efficient and green way for the treatment of upgrading wastewater, which utilize the LUW as natural resources instead of purifying and discharging.