Thymol confers tolerance to salt stress by activating anti-oxidative defense and modulating Na+ homeostasis in rice root.

Modulation of plant salt tolerance has been drawing great attention. Thymol is a kind of natural chemical that has been developed as anti-microbial reagent and medicine. To date, we still have limited knowledge about thymol-modulated plant physiology. In this work, physiological, histochemical, and biochemical methods were adopted to study thymol-conferred salt resistance in the root of rice (Oryza sativa). Thymol significantly rescued root growth under salt stress. Thymol ameliorated cell membrane damage, oxidative stress, ROS accumulation, and cell death in roots under salt stress. Thymol-attenuated oxidative stress may be resulted from the activation of anti-oxidative capacity, including both enzymatic and non-enzymatic system. Thymol treatment significantly decreased Na+ content in root cells upon salt stress, which might be ascribed to the upregulation of OsSOS1 (salt overly sensitive 1) facilitating Na+ exclusion. In addition, thymol stimulated the expression of genes encoding tonoplast OsNHX (Na+/H+antiporter), which may help root cells to compartmentalize Na+ in vacuole. The results of these works evidenced that thymol was capable of inducing salt tolerance by reestablishing ROS homeostasis and modulating cellular Na+ flux in rice roots. These findings may be applicable to improve crop growth in salinity area.

Microbial N Transformations and N2O Emission after Simulated Grassland Cultivation: Effects of the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP).

Grassland cultivation can mobilize large pools of N in the soil, with the potential for N leaching and N2O emissions. Spraying with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) before cultivation was simulated by use of soil columns in which the residue distribution corresponded to plowing or rotovation to study the effects of soil-residue contact on N transformations. DMPP was sprayed on aboveground parts of ryegrass and white clover plants before incorporation. During a 42-day incubation, soil mineral N dynamics, potential ammonia oxidation (PAO), denitrifying enzyme activity (DEA), nitrifier and denitrifier populations, and N2O emissions were investigated. The soil NO3- pool was enriched with 15N to trace sources of N2O. Ammonium was rapidly released from decomposing residues, and PAO was stimulated in soil near residues. DMPP effectively reduced NH4+ transformation irrespective of residue distribution. Ammonia-oxidizing archaea (AOA) and bacteria (AOB) were both present, but only the AOB amoA transcript abundance correlated with PAO. DMPP inhibited the transcription of AOB amoA genes. Denitrifier genes and transcripts (nirK, nirS, and clades I and II of nosZ) were recovered, and a correlation was found between nirS mRNA and DEA. DMPP showed no adverse effects on the abundance or activity of denitrifiers. The 15N enrichment of N2O showed that denitrification was responsible for 80 to 90% of emissions. With support from a control experiment without NO3- amendment, it was concluded that DMPP will generally reduce the potential for leaching of residue-derived N, whereas the effect of DMPP on N2O emissions will be significant only when soil NO3- availability is limiting. IMPORTANCE: Residue incorporation following grassland cultivation can lead to mobilization of large pools of N and potentially to significant N losses via leaching and N2O emissions. This study proposed a mitigation strategy of applying 3,4-dimethylpyrazole phosphate (DMPP) prior to grassland cultivation and investigated its efficacy in a laboratory incubation study. DMPP inhibited the growth and activity of ammonia-oxidizing bacteria but had no adverse effects on ammonia-oxidizing archaea and denitrifiers. DMPP can effectively reduce the potential for leaching of NO3- derived from residue decomposition, while the effect on reducing N2O emissions will be significant only when soil NO3- availability is limiting. Our findings provide insight into how DMPP affects soil nitrifier and denitrifier populations and have direct implications for improving N use efficiency and reducing environmental impacts during grassland cultivation.

Assessment of flavor characteristics in snakehead (Ophiocephalus argus Cantor) surimi gels affected by atmospheric cold plasma treatment using GC-IMS.

The gel formation ability of freshwater surimi is weak, resulting in its poor flavor and quality. Atmospheric cold plasma (ACP), a widely developed non-thermal processing technology in the food industry, is considered to have potential applications in maintaining and improving the flavor characteristics of surimi gels. In this study, the effect of ACP on snakehead surimi gels flavor at different treatment times was investigated by sensory evaluation and gas chromatography-ion mobility spectrometry (GC-IMS) analysis. The results showed that ACP could better maintain and improve the original appearance and tissue state characteristics of surimi gels, scoring about 1-2 points higher than the ACP-untreated group. GC-IMS analysis demonstrated the obvious difference in the volatile organic compounds (VOCs) among the treatment groups. Specifically, the samples treated for 120 s with ACP exhibited the most unique aroma characteristics, which probably related to the highest thiobarbituric acid reactive substances values (73.28 µmol MDA/kg sample). Meanwhile, the reduced TCA-soluble peptides content indicated that ACP could inhibit protein degradation to maintaining the tissue state and flavor characteristics of the surimi gels. In conclusion, the advantages of ACP treatment, such as little damage to nutrients, and maximum retention of original sensory properties, provide new ideas for its application in the flavor characteristics of the snakehead surimi gels.