Combined effects of biochar and biodegradable mulch film on chromium bioavailability and the agronomic characteristics of tobacco.

Biochar (BC) and biodegradable mulch film (BMF) are both commonly used means of production in agriculture. In recent years, most studies have focused on the effects of BC or BMF on soil heavy metal pollution, while they have neglected the combined effects. In this study, a pot experiment was conducted to examine the impacts of BMF, BC, and combined BMF and BC (CMB) on the mobility of chromium (Cr) and the agronomic characteristics of flue-cured tobacco. Compared with the control, BMF, BC, and CMB significantly reduced the concentrations of diethylenetriamine pentaacetic acid (DTPA) extractable Cr in soils by 29.07-29.75%, 45.35-48.54%, and 34.21-37.92%, respectively. In comparison to the application of BMF and BC alone, co-application reduced the availability of Cr in soil via increasing the adsorption of soil Cr and soil enzyme activity, which resulted in the decrease of Cr content and bioconcentration factor and in plants. Moreover, the combined application increased the plant height, stem diameter, leaf area, total root area, root tip number, and root activity of tobacco, which leaded to increase in leaf and root biomass by 11.40-67.01% and 23.91-50.74%, respectively. Therefore, the application of CMB can reduce the heavy metal residues in tobacco leaves and improve tobacco yield and quality.

Response of soil N2O production pathways to biochar amendment and its isotope discrimination methods.

Reducing nitrous oxide (N2O) emission from farmland is crucial for alleviating global warming since agriculture is an important contributor of atmospheric N2O. Returning biochar to agricultural fields is an important measure to mitigate soil N2O emissions. Accurately quantifying the effect of biochar on the process of N2O production and its driving factors is critical for achieving N2O emission mitigation. Recently, stable isotope techniques such as isotope labeling, natural abundance, and site preference (SP) value, have been widely used to distinguish N2O production pathways. However, the different isotope methods have certain limitations in distinguishing N2O production in biochar-amended soils where it is difficult to identify the relative contribution of individual pathways for N2O production. This paper systematically reviews the pathways of soil N2O production (nitrification, nitrifier denitrification, bacterial denitrification, fungal denitrification, coupled nitrification-denitrification, dissimilatory nitrate reduction to ammonium and abiotic processes) and their response mechanism to the addition of biochar, as well as the development history and advantages of isotopes in differentiating N2O production pathways in biochar-amended soils. Moreover, the limitations of current research methods and future research directions are proposed. These results will help resolve how biochar affects different processes that lead to soil N2O generation and provide a scientific basis for sustainable agricultural carbon sequestration and the fulfilment of carbon neutrality goals.

Development and Application of Portable Reflectometric Spectroscopy Combined with Solid-Phase Extraction for Determination of Potassium in Flue-Cured Tobacco Leaves.

Potassium (K) plays important roles in the energy and substance conversion of tobacco metabolism and is also regarded as one of the important indicators of tobacco quality evaluation. However, the K quantitative analytical method shows poor performance in terms of being easy-to-use, cost-effective, and portable. Here, we developed a rapid and simple method for the determination of K content in flue-cured tobacco leaves, including water extraction with 100 °C heating, purification with solid-phase extraction (SPE), and analysis with portable reflectometric spectroscopy based on K test strips. The method development consisted of optimization of the extraction and test strip reaction conditions, screening of SPE sorbent materials, and evaluation of the matrix effect. Under the optimum conditions, good linearity was observed in 0.20-0.90 mg/mL with a correlation coefficient >0.999. The extraction recoveries were found to be in the range of 98.0-99.5% with a repeatability and reproducibility of 1.15-1.98% and 2.04-3.26%, respectively. The sample measured range was calculated to be 0.76-3.68% K. Excellent agreement was found in accuracy between the developed reflectometric spectroscopy method and the standard method. The developed method was applied to analyze the K content in different cultivars, and the content varied greatly among the samples with lowest and highest contents for Y28 and Guiyan 5 cultivars, respectively. This study can provide a reliable approach for K analysis, which may become available on-site in a quick on-farm test.

Determination of Residual Diisocyanates and Related Diamines in Biodegradable Mulch Films Using N-Ethoxycarbonylation Derivatization and GC-MS.

Diisocyanates are highly reactive compounds with two functional isocyanate groups. The exposure of diisocyanates is associated with severely adverse health effects, such as asthma, inflammation in the respiratory tract, and cancer. The hydrolysis product from diisocyanates to related diamines is also a potential carcinogen. Here, we developed an effective, accurate, and precise method for simultaneous determination of residual diisocyanates and related diamines in biodegradable mulch films, based on N-ethoxycarbonylation derivatization and gas chromatography-mass spectrometry. The method development included the optimization of ultrasonic hydrolysis and extraction, screening of N-ethoxycarbonylation conditions with ethyl chloroformate, evaluation of the diamines degradation, and analysis of the fragmentation mechanisms. Under the optimum experimental conditions, good linearity was observed with R2 > 0.999. The extraction recoveries were found in the range of 93.9−101.2% with repeatabilities and reproducibilities in 0.89−8.12% and 2.12−10.56%, respectively. The limits of detection ranged from 0.0025 to 0.057 µg/mL. The developed method was applied to commercial polybutylene adipate co-terephthalate (PBAT) biodegradable mulch film samples for analysis of the diverse residual diisocyanates and related diamine additives. The components varied greatly among the sample from different origin. Overall, this study provides a reliable method for assessing safety in biodegradable mulch films.

Chiral determination of nornicotine, anatabine and anabasine in tobacco by achiral gas chromatography with (1S)-(-)-camphanic chloride derivatization: Application to enantiomeric profiling of cultivars and curing processes.

The alkaloid enantiomers are well-known to have different physiological and pharmacological effects, and to play an important role in enantioselectivity metabolism with enzymes catalysis in tobacco plants. Here, we developed an improved method for simultaneous and high-precision determination of the individual enantiomers of nornicotine, anatabine and anabasine in four tobacco matrices, based on an achiral gas chromatography-nitrogen phosphorus detector (GCNPD) with commonly available Rtx-200 column using (1S)-(-)-camphanic chloride derivatization. The method development consists of the optimization of extraction and derivatization, screening of achiral column, analysis of the fragmentation mechanisms and evaluation of matrix effect (ME). Under the optimized experimental conditions, the current method exhibited excellent detection capability for the alkaloid enantiomers, with coefficients of determination (R2) > 0.9989 and normality test of residuals P > 0.05 in linear regression parameters. The ME can be neglected for the camphanic derivatives. The limit of detection (LOD) and limit of quantitation (LOQ) ranged from 0.087 to 0.24 µg g - 1 and 0.29 to 0.81 µg g - 1, respectively. The recoveries and within-laboratory relative standard deviations (RSDR) were 94.3%~104.2% and 0.51%~3.89%, respectively. The developed method was successfully applied to determine the enantiomeric profiling of cultivars and curing processes. Tobacco cultivars had a significant impact on the nornicotine, anatabine, anabasine concentration and enantiomeric fraction (EF) of (R)-nornicotine, whereas the only significant change induced by the curing processes was an increase in the EF of (R)-anabasine.

An improved in situ acetylation with dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry for the sensitive determination of phenols in mainstream tobacco smoke.

Phenols in tobacco smoke can adversely affect health with serious consequences that include cardiovascular toxicity, tumor promotion and genotoxic activity. Hence, an improved method involving in situ acetylation and dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the determination of 39 phenols in mainstream tobacco smoke (MTS). The in situ acetylation was optimized using four protocols, after which the effects of experimental variables on acetylation efficiency were studied using a multifactorial experimental design. The optimum conditions were found to involve an initial 75 µL volume of acetic anhydride, 140 mg of NaHCO3 and 72 mg of K2CO3. The phenolic acetates were then subjected to DLLME, after which they were identified and quantified by GC-MS. A total of 32 additional phenols were tentatively identified. Good linearity was observed with R > 0.999 and each lack-of-fit P > 0.05. The relative recoveries were in the range of 94.8-104.3% with repeatabilities and reproducibilities less than 5.5% and 6.8%, respectively. The limits of detection ranged from 1.12 to 1.74 ng cig-1, with high enrichment factors between 87 and 144. This method was applied to the MTS from three commercial cigarettes with different tar levels. The results provide valuable information for assessing the risks of phenols.

Exogenous trehalose improves growth under limiting nitrogen through upregulation of nitrogen metabolism.

BACKGROUND: The trehalose (Tre) pathway has strong effects on growth and development in plants through regulation of carbon metabolism. Altering either Tre or trehalose 6-phosphate (T6P) can improve growth and productivity of plants as observed under different water availability. As yet, there are no reports of the effects of modification of Tre orT6P on plant performance under limiting nutrition. RESULTS: Here we report that nitrogen (N) metabolism is positively affected by exogenous application of Tre in nitrogen-deficient growing conditions. Spraying foliage of tobacco (Nicotiana tabacum) with trehalose partially alleviated symptoms of nitrogen deficiency through upregulation of nitrate and ammonia assimilation and increasing activities of nitrate reductase (NR), glycolate oxidase (GO), glutamine synthetase (GS) and glutamine oxoglutarate aminotransferase (GOGAT) with concomitant changes in ammonium (NH4+) and nitrate (NO3-) concentrations, glutamine and amino acids. Chlorophyll and total nitrogen content of leaves and rates of photosynthesis were increased compared to nitrogen-deficient plants without applied Tre. Total plant biomass accumulation was also higher in Tre -fed nitrogen-deficient plants, with a smaller proportion of dry weight partitioned to roots, compared to nitrogen-deficient plants without applied Tre. Consistent with higher nitrogen assimilation and growth, Tre application reduced foliar starch. Minimal effects of Tre feeding were observed on nitrogen-sufficient plants. CONCLUSIONS: The data show, for the first time, significant stimulatory effects of exogenous Tre on nitrogen metabolism and growth in plants growing under deficient nitrogen. Under such adverse conditions metabolism is regulated for survival rather than productivity. Application of Tre can alter this regulation towards maintenance of productive functions under low nitrogen. This has implications for considering approaches to modifying the Tre pathway for to improve crop nitrogen-use efficiency and production.