Exogenous application and interaction of biochar with environmental factors for improving functional diversity of rhizosphere's microbial community and health.

The usage of fertilizer with high nitrogen content in many countries, as well as its enormous surplus, has a negative impact on the soil ecological environment in agricultural system. This consumption of nitrogen fertilizer can be minimized by applying biochar to maintain the sufficient supply of nitrogen as nutrient to the near-root zone. This study investigated the effects of various amounts of biochar application (450, 900, 1350, and 1800 kg/hm2) and reduction of nitrogen fertilizer amount (10, 15, 20, and 25%) on the nutrients and microorganism community structure in rhizosphere growing tobacco plant. The microorganism community was found essential in improving nitrogen retention. Compared with conventional treatment, an application of biochar in rhizosphere soil increased the content of soil available phosphorus, organic matter and total nitrogen by 21.47%, 26.34%, and 9.52%, respectively. It also increased the abundance of microorganisms that are capable of degrading and utilizing organic matter and cellulose, such as Actinobacteria and Acidobacteria. The relative abundance of Chloroflexi was also increased by 49.67-78.61%, and the Acidobacteria increased by 14.79-39.13%. Overall, the application of biochar with reduced nitrogen fertilizer amount can regulate the rhizosphere microecological environment of tobacco plants and their microbial population structure, thereby promoting soil health for tobacco plant growth while reducing soil acidification and environmental pollution caused by excessive nitrogen fertilizer.

Soil carbon supplementation: Improvement of root-surrounding soil bacterial communities, sugar and starch content in tobacco (N. tabacum).

Soil carbon supplementation is known to stimulate plant growth by improving soil fertility and plant nutrient uptake. However, the underlying process and chemical mechanism that could explain the interrelationship between soil carbon supplementation, soil micro-ecology, and the growth and quality of plant remain unclear. In this study, we investigated the influence and mechanism of soil carbon supplementation on the bacterial community, chemical cycling, mineral nutrition absorption, growth and properties of tobacco leaves. The soil carbon supplementation increased amino acid, carbohydrates, chemical energy metabolism, and bacterial richness in the soil. This led to increased content of sugar (23.75%), starch (13.25%), and chlorophyll (10.56%) in tobacco leaves. Linear discriminant analysis revealed 49 key phylotypes and significant increment of some of the Plant Growth-Promoting Rhizobacteria (PGPR) genera (Bacillus, Novosphingobium, Pseudomonas, Sphingomonas) in the rhizosphere, which can influence the tobacco growth. Partial Least Squares Path Modeling (PLS-PM) showed that soil carbon supplementation positively affected the sugar and starch contents in tobacco leaves by possibly altering the photosynthesis pathway towards increasing the aroma of the leaves, thus contributing to enhanced tobacco flavor. These findings are useful for understanding the influence of soil carbon supplementation on bacterial community for improving the yields and quality of tobacco in industrial plantation.

Biochar increases tobacco yield by promoting root growth based on a three-year field application.

In order to explore the effects of biochar on root system and growth characteristics of flue-tobacco, three years of field experiments were conducted to study the influence of different biochar application levels [600 (T1), 1200 (T2), 1800(T3), 2400 (T4), 3000 (T5) kg/ha] and no fertilizer (CK) on the root physiological indexes and growth index of tobacco. Compared with local conventional fertilization, the application rate of N fertilizer in each treatment (except for control) was reduced by 40% to analyze the effects of different amount of biochar on the physiological indexes of tobacco roots and leaf photosynthesis during flourishing. The results showed that tobacco plants' root development status in the flourishing period was consistent with the photosynthetic physiological indexes, chlorophyll content, and leaf-area coefficient. Compared with the control, the application of biochar could increase the root vigor by 177.8%. Biochar improved the roots, increasing the total root area by 91.35% and the number of root tips by 100.9%. Meanwhile, biochar increased the net photosynthetic rate of tobacco leaves by 77.3% and the total tobacco biomass by 72.5%. Studies have shown that biochar can promote the development of tobacco roots, and then enhance the photosynthesis of leaves, so that tobacco plants can grow healthily, which is conducive to the tobacco production and the cultivation of soil.

Prediction of Microvascular Invasion in Hepatocellular Carcinoma With a Multi-Disciplinary Team-Like Radiomics Fusion Model on Dynamic Contrast-Enhanced Computed Tomography.

OBJECTIVE: To investigate microvascular invasion (MVI) of HCC through a noninvasive multi-disciplinary team (MDT)-like radiomics fusion model on dynamic contrast enhanced (DCE) computed tomography (CT). METHODS: This retrospective study included 111 patients with pathologically proven hepatocellular carcinoma, which comprised 57 MVI-positive and 54 MVI-negative patients. Target volume of interest (VOI) was delineated on four DCE CT phases. The volume of tumor core (V tc ) and seven peripheral tumor regions (V pt , with varying distances of 2, 4, 6, 8, 10, 12, and 14 mm to tumor margin) were obtained. Radiomics features extracted from different combinations of phase(s) and VOI(s) were cross-validated by 150 classification models. The best phase and VOI (or combinations) were determined. The top predictive models were ranked and screened by cross-validation on the training/validation set. The model fusion, a procedure analogous to multidisciplinary consultation, was performed on the top-3 models to generate a final model, which was validated on an independent testing set. RESULTS: Image features extracted from V tc +V pt(12mm) in the portal venous phase (PVP) showed dominant predictive performances. The top ranked features from V tc +V pt(12mm) in PVP included one gray level size zone matrix (GLSZM)-based feature and four first-order based features. Model fusion outperformed a single model in MVI prediction. The weighted fusion method achieved the best predictive performance with an AUC of 0.81, accuracy of 78.3%, sensitivity of 81.8%, and specificity of 75% on the independent testing set. CONCLUSION: Image features extracted from the PVP with V tc +V pt(12mm) are the most reliable features indicative of MVI. The MDT-like radiomics fusion model is a promising tool to generate accurate and reproducible results in MVI status prediction in HCC.

Biochar for cadmium pollution mitigation and stress resistance in tobacco growth.

Pot experiments were conducted to investigate the influence of biochar addition and the mechanisms that alleviate Cd stress in the growth of tobacco plant. Cadmium showed an inhibitory effect on tobacco growth at different post-transplantation times, and this increased with the increase in soil Cd concentration. The growth index decreased by more than 10%, and the photosynthetic pigment and photosynthetic characteristics of the tobacco leaf were significantly reduced, and the antioxidant enzyme activity was enhanced. Application of biochar effectively alleviated the inhibitory effect of Cd on tobacco growth, and the alleviation effect of treatments is more significant to the plants with a higher Cd concentration. The contents of chlorophyll a, chlorophyll b, and carotenoids in the leaves of tobacco plants treated with biochar increased by 9.99%, 12.58%, and 10.32%, respectively, after 60 days of transplantation. The photosynthetic characteristics index of the net photosynthetic rate increased by 11.48%, stomatal conductance increased by 11.44%, and intercellular carbon dioxide concentration decreased to 0.92. Based on the treatments, during the growth period, the antioxidant enzyme activities of tobacco leaves comprising catalase, peroxidase, superoxide dismutase, and malondialdehyde increased by 7.62%, 10.41%, 10.58%, and 12.57%, respectively, after the application of biochar. Our results show that biochar containing functional groups can effectively reduce the effect of Cd stress by intensifying the adsorption or passivation of Cd in the soil, thereby, significantly reducing the Cd content in plant leaves, and providing a theoretical basis and method to alleviate soil Cd pollution and effect soil remediation.

Magnetic Resonance Imaging (MRI) Phenotypes May Provide Additional Information for Risk Stratification for Encapsulated Papillary Carcinoma of the Breast.

BACKGROUND: Encapsulated papillary carcinoma (EPC) of the breast is a rare entity. EPC can be underappreciated on percutaneous biopsy, which may require additional procedures if invasion is not recognized preoperatively. We aimed to investigate the magnetic resonance imaging (MRI) phenotypes correlated with preoperative pathological risk stratification for clinical guidance. MATERIALS AND METHODS: The preoperative MRI scans of 30 patients diagnosed with 36 EPCs in multiple centers between August 2015 and February 2020 were reviewed by two breast radiologists. According to the WHO classification published in 2019, EPCs were classified into two pathological subtypes: encapsulated papillary carcinoma and encapsulated papillary carcinoma with invasion. Clinicopathological analysis of the two subtypes and MR feature analysis were performed. RESULTS: Evaluation of the MRI phenotypes and pathological subtype information revealed that not circumscribed (P=0.04) was more common in EPCs with invasion than in EPCs. There was a significant difference in the age of patients (P=0.05), and the risk increased with age. The maximum diameter of the tumor increased with tumor risk, but there was no significant difference (P=0.36). Nearly half of the EPC with invasion patients showed hyperintensity on T1WI (P=0.19). A total of 63.6% of the EPC with invasion group showed non-mass enhancement surrounding (P=0.85). In addition, 29 patients (96.7%) had no axillary lymph node metastasis, and only one patient with EPC with invasion had axillary lymph node metastasis. Further pathological information analysis of EPCs showed that higher Ki-67 levels were more common in patients with EPCs with invasion (P=0.04). A total of 29 patients (96.7%) had the luminal phenotype, and one patient with EPC with invasion had the Her-2-positive phenotype. CONCLUSION: The margin, age and Ki-67 level were the key features for EPC risk stratification. In addition, these MRI signs, including a larger tumor, non-mass enhancement surrounding and axillary lymph node metastasis, may be suggestive of a high-risk stratification. Therefore, MRI phenotypes may provide additional information for the risk stratification of EPCs.

Novel environmental factors affecting microbial responses and physicochemical properties by sequentially applied biochar in black soil.

Biochar was increasingly used in agriculture soil amendment and has received widespread attention due to its potential to improve soil micro-ecological environment and crop growth. The raw material of the biochar used in this study is peanut shell, which is mixed with other organics and minerals to become a mineral-enhanced biochar under heating conditions (220 °C). When the third season crop is finished, we evaluated black soil physicochemical properties, microbial communities, and crop growth in long-term agricultural trials. Four treatments were set up: no amendment (control CK), nitrogen fertilizer only (70 kg ha-1 N), enhanced biochar only (5 t ha-1 B), and nitrogen fertilizer (70 kg ha-1) + enhanced biochar (5 t ha-1) (NB). The enhanced biochar promotes crop growth and increased the richness of the bacterial community, while reducing the richness of the fungal community. Nitrogen fertilizer + enhanced biochar increased soil microbial biomass carbon, nitrate nitrogen, and ammonium nitrogen by 43.75, 7.25, and 19.28%. In addition, we found changes in bacterial community were closely related to soil organic carbon, while changes in fungal community structure were closely related to soil carbon to nitrogen ratio. And the soil organic carbon and soil carbon to nitrogen ratio of biochar treatment were increased by 5.64 and 6.25% compared with fertilizer treatment, respectively. We concluded that enhanced biochar improved the soil more effectively and made the soil more conducive to crop growth. Regulating the microbial community by improving the physicochemical properties of soil was an important way to improve the stability and condition of the soil system with biochar. An enhanced biochar was of great significance for circular development of agriculture and soil improvement in Northeast China.

Influence of Soil Organic Carbon on the Aroma of Tobacco Leaves and the Structure of Microbial Communities.

The soil organic carbon is associated with the plant quality and the microbial community structure. In the present study, carbon fertilizers were applied to paddy soil to elucidate the relationship between soil carbon and neutral aroma substances in both tobacco and soil microbiome by transcriptome sequencing and 16S rDNA-based analysis, respectively. Our results showed that (1) the increase in soil carbon content was closely correlated with the abundance of microorganisms belonging to two classes (which could potentially affect tobacco plants), namely Gammaproteobacteria and Chloroflexia, (2) soil carbon apparently affected tobacco neutral aroma substances, and (3) soil carbon improved neutral aroma substances by affecting the transcriptional processes of sesquiterpenoid and chlorophyll biosyntheses. These results suggest that increased soil carbon-especially active organic carbon-resulted in desirable improvements in aroma substances in tobacco leaves.

Transcriptome sequencing reveals the effect of biochar improvement on the development of tobacco plants before and after topping.

The application of biochar is one of the most useful methods for improving soil quality, which is of the utmost significance for the continuous production of crops. As there are no conclusive studies on the specific effects of biochar application on tobacco quality, this study aimed to improve the yield and quality of tobacco as a model crop for economic and genetic research in southern China, by such application. We used transcriptome sequencing to reveal the effects of applied biochar on tobacco development before and after topping. Our results showed that topping affected carbon and nitrogen metabolism, photosynthesis and secondary metabolism in the tobacco plants, while straw biochar-application to the soil resulted in amino acid and lipid synthesis; additionally, it affected secondary metabolism of the tobacco plants through carbon restoration and hormonal action, before and after topping. In addition to the new insights into the impact of biochar on crops, our findings provide a basis for biochar application measures in tobacco and other crops.

Biochar application significantly affects the N pool and microbial community structure in purple and paddy soils.

BACKGROUND: The increasing demand for food production has resulted in the use of large quantities of chemical fertilizers. This has created major environmental problems, such as increased ammonia volatilization, N2O emission, and nitrogen (N) leaching from agricultural soil. In particular, the utilization rate of N fertilizer is low in subtropical southern parts of China due to high rainfall. This causes not only large financial losses in agriculture, but also serious environmental pollution. METHODS: In this study, 16S rDNA-based analysis and static-chamber gas chromatography were used to elucidate the effects of continuous straw biochar application on the N pool and bacteria environment in two typical soil types, purple and paddy soils, in southern China. RESULTS: Straw biochar application (1) improved the soil N pool in both rhizosphere and non-rhizosphere soils; (2) significantly reduced the emission of N2O, with no difference in emission between 1 and 2 years of application; (3) increased the abundance of N-processing bacteria in the soil and altered the bacterial community structure; and (4) improved the tobacco yield and N use efficiency in paddy soil. These findings suggest that, in southern China, the application of straw biochar can promote N transformation in purple and paddy soils and reduce the emission of the greenhouse gas N2O.

Metagenomic insights into effects of wheat straw compost fertiliser application on microbial community composition and function in tobacco rhizosphere soil.

The application of fertilisers incorporated with plant residues improves nutrient availability in soils, which shifts the microbial community structure and favours plant growth. To understand the impact of wheat straw compost fertiliser on soil properties and microbial community structure, tobacco planting soils were treated with four different fertilisers using varied amounts of straw compost fertiliser and a no fertiliser control (CK). Results showed that different fertilisers affected available soil nutrient contents differently. Treatment of tobacco soil with application of combined chemical fertiliser/wheat straw compost led to improved soil chemical properties, and increased soil organic matter and available phosphorus and potassium content. Treatment with FT1 200 kg/mu straw was found to be superior in improving soil fertility. Metagenomic DNA sequencing revealed that different fertiliser treatments resulted in changes in the microbial community composition. In soil treated with FT2 300 kg/mu straw for 60 days, the predominant bacterial phyla were Proteobacteria, Actinobacteria, and Verrucomicrobia, whereas Cyanobacteria, Basidiomycota, and Chlorophyta were found in high abundance in soil samples treated with FT1 200 kg/mu straw for 30 days. Functional annotation of metagenomic sequences revealed that genes involved in metabolic pathways were among the most abundant type. PCoA analysis clearly separated the samples containing straw compost fertiliser and chemical fertiliser. A significant correlation between soil properties and the dominant phyla was identified.

[Effect of Long-Term Biochar Application on Soil Respiration in Flue-Cured Tobacco Planting Fields in Henan Province].

A five year (2013-2017) experiment was conducted to explore the effects of biochar application on the dynamic changes in soil respiration, soil water, and heat factors under four treatments:CK (without biochar), T1 (with 1.5 t·hm-2biochar), T2 (with 15 t·hm-2biochar), and T3 (with 45 t·hm-2biochar). The results showed that:① the soil respiration rate in the growing season of flue-cured tobacco was significantly reduced by 25.89% under the five year application of medium-dose biochar (T2:15 t·hm-2) in soil, while it was significantly increased by 21.48% when the applied dose increased to 45 t·hm-2(T3) (P<0.05). ② The long-term application of medium-dose biochar in the soil significantly reduced the soil heterotrophic respiration and autotrophic respiration rates by 29.80% and 28.75%, respectively. Meanwhile, the application of high-dose biochar (T3:45 t·hm-2) significantly increased the heterotrophic respiration rate by 28.88%. In addition, the application of low-dose biochar (T1:1.5 t·hm-2) and medium-dose biochar significantly increased the proportion of autotrophic respiration, whereas the high-dose biochar application significantly increased the proportion of heterotrophic respiration (P<0.05). ③ The addition of low-dose biochar to the soil significantly reduced the soil temperature at 5 cm in the growing season of flue-cured tobacco, while the high-dose application significantly reduced the soil humidity. There was a significant index correlation between soil respiration and soil temperature at 5 cm but no significant correlation with soil humidity at 5 cm (P<0.05). Ultimately, the application of low-dose biochar for five years in soil had no effect on soil respiration, and the application of the proper amount of biochar had a carbon sequestration effect. Additionally, large-dose biochar application may be counterproductive. It is recommended that the application range of biochar should be controlled within 15 t·hm-2.

Influence of high-carbon basal fertiliser on the structure and composition of a soil microbial community under tobacco cultivation.

Soil microorganisms play a crucial role in cycling soil nutrients and providing organic nutrients for plant growth and development. Fertilisation balances soil fertility and quality, and affects soil microbial communities. Fertilisation is a frontier subject in agricultural and environmental sciences. Here we showed that the application of high-carbon basal fertiliser treatment could improve the tobacco yield and quality when compared to chemical fertiliser, high-carbon basal fertiliser and mixed high-carbon chemical fertiliser. The potential reason is that different fertiliser treatments influence soil fertility, such as nitrogen, phosphorus, and other contents, besides soil organic matter. Further experiments revealed that populations of bacteria, fungi and actinomycetes fluctuated during tobacco development under different fertilisation treatments. Then we performed high-throughput sequencing of the 16S rRNA gene, and the results showed that the fertilisation treatments had significant effects on the microbial community, particularly within the finer taxonomic divisions or non-dominant taxa. Moreover, proteobacteria and fungal genera had significantly different relative abundances during tobacco growth under various tobacco developmental stages and fertilisation treatments. These results indicated that mixed high-carbon chemical fertiliser could improve soil fertility by influencing the soil microorganism, and that the fertilisation treatments impacted on the structure and composition of the microbial community, and especially the diversity of non-dominant taxa. However, more studies are needed to confirm their reliability.

[Effects of phosphorus fertilizer on the root system and its relationship with the aboveground part of flue-cured tobacco].

Using 'Yuyan 10' as the material, the effects of different phosphorus fertilizer application on root characteristics of tobacco, such as root dry mass and the difference of dry matter distribution and mineral nutrient accumulation between its above and underground parts were investigated. The results showed that the growth of flue-cured tobacco root system and the distribution of dry matter to the aboveground part were significantly promoted by phosphorus fertilizer application. The application of 30 kg P2O5 · hm(-2) led to the maximums of root dry mass, root volume, root activity and the minimum of root to shoot ratio. The maximum nutrient accumulation rates of root and leaf appeared 57-66 days after transplanting and 44-55 days after transplanting, respectively. Phosphorus could not only promote the mineral nutrition absorption of tobacco and the earlier appearance of maximum nutrient accumulation, but significantly promote the nutrient accumulation of the aboveground part. But, the positive effects described above would be weakened when the amount of phosphorus fertilizer was more than 30 kg P2O5 · hm(-2). Therefore, it's necessary to control the amount of phosphorus application to improve the quality of tobacco leaves.

[Signal intensity-time curve and quantitative dynamic contrast-enhanced magnetic resonance imaging in differentiating neoplasms of uterus].

OBJECTIVE: To evaluate signal intensity-time (SI-Time) curve and quantitative dynamic contrast-enhanced 3.0T magnetic resonance imaging in diagnosis and differentiating neoplasm of uterus.
 METHODS: A total of 42 cases of uterine neoplasm (20 were malignant and 22 were benign) were evaluated in our study. All cases received dynamic contrast-enhanced scanning on 3.0T MRI. The raw data was processed by Siemens Tissue 4D software and the SI-Time curve was obtained and analyzed. Pharmacokinetic modeling of Tofts with a modeled vascular input function was used for calculating volume parameters: volume transfer constant (Ktrans), reverse volume transfer constant (Kep), the extravascular extracellular space volume per unit volume of tissue (Ve). The correlation of these parameters at each groups were investigated. The SI-Time curve and the data of perfusion parameters between the 2 groups were compared by T test.
 RESULTS: Among 20 malignant tumors, 12 were cervical carcinoma and 8 were endometrial cancer. Among the benign tumors, 13 were leiomyomas, 3 were endometrial polyp, 3 were endometrial hyperplasia, and 3 were adenomyosis. 59.1% cases of benign tumors belong to Type I curve and 65% cases of malignant tumors belong to Type II curve. There was significant difference in SI-Time curve between benign and malignant tumors (P=0.011). If Type I curve was used as diagnostic criteria for benign tumors, and Type II and III curve were for malignant tumors, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value were 90.0%, 59.1%, 66.7%, and 86.7%, respectively. Ve was 0.477 ± 0.143 in malignant and 0.614 ± 0.146 in control group with significant difference (P=0.004). Ve was 0.477 ± 0.143 in malignant and 0.589 0.176 in benign group with significant difference (P=0.004). Ktrans was (0.178 ± 0.067) min⁻¹ in malignant and (0.263 ± 0.111) min⁻¹ in control group with significant difference (P=0.003). Ktrans was (0.182 ± 0.096) min⁻¹ in benign and (0.263 ± 0.111) min⁻¹ in control group with significant difference (P=0.011). 
 CONCLUSION: The type of SI-Time curve and perfusion parameters were important for differentiating benign and malignant uterine tumors in dynamic enhanced MRI. These parameters provide a supplement for conventional morphological MR diagnosis.

Cloning and characterization of SnRK2 subfamily II genes from Nicotiana tabacum.

SnRK2 is a plant-specific protein kinase family involved in abiotic stress signalling. In this study, NtSnRK2.1, NtSnRK2.2, and NtSnRK2.3, were cloned from tobacco by in silico cloning and reverse transcription PCR. The three protein kinases were classed into subfamily II of the SnRK2 family using a phylogenetic tree and C-terminus analysis. Subcellular localization revealed NtSnRK2s in the nuclear and cytoplasmic compartments. Dynamic expression of NtSnRK2s in tobacco plants that were exposed to drought, salt, or cold stressors were characterised using quantitative real-time PCR. It was revealed that the three genes showed similar patterns of transcription under abiotic stress responses; there was evidence NtSnRK2s participated in abscisic acid-dependent signalling pathways. NtSnRK2.1-3 responded much faster to drought and salt than to cold stress. To investigate the role of NtSnRK2s under abiotic stresses, NtSnRK2.1 gene was over-expressed in tobacco. A stress tolerance assay showed that tobacco plants that over-expressed NtSnRK2.1 plants had greater salt tolerance. The results indicate that NtSnRK2s are involved in abiotic stress response pathways.

Differentiation of central lung cancer from atelectasis: comparison of diffusion-weighted MRI with PET/CT.

OBJECTIVE: Prospectively assess the performance of diffusion-weighted magnetic resonance imaging (DW-MRI) for differentiation of central lung cancer from atelectasis. MATERIALS AND METHODS: 38 consecutive lung cancer patients (26 males, 12 females; age range: 28-71 years; mean age: 49 years) who were referred for thoracic MR imaging examinations were enrolled. MR examinations were performed using a 1.5-T clinical scanner and scanning sequences of T1WI, T2WI, and DWI. Cancers and atelectasis were measured by mapping of the apparent diffusion coefficients (ADCs) obtained with a b-value of 500 s/mm(2). RESULTS: PET/CT and DW-MR allowed differentiation of tumor and atelectasis in all 38 cases, but T2WI did not allow differentiation in 9 cases. Comparison of conventional T2WI and DW-MRI indicated a higher contrast noise ratio of the central lung carcinoma than the atelectasis by DW-MRI. ADC maps indicated significantly lower mean ADC in the central lung carcinoma than in the atelectasis (1.83±0.58 vs. 2.90±0.26 mm(2)/s, p<0.0001). ADC values of small cell lung carcinoma were significantly greater than those from squamous cell carcinoma and adenocarcinoma (p<0.0001 for both). CONCLUSIONS: DW-MR imaging provides valuable information not obtained by conventional MR and may be useful for differentiation of central lung carcinoma from atelectasis. Future developments may allow DW-MR imaging to be used as an alternative to PET-CT in imaging of patients with lung cancer.

Low nitrogen-induced expression of cyclophilin in Nicotiana tabacum.

Leaf morphology and the leaf protein expression profiles of flue-cured tobacco grown in central Henan province of China under low nitrogen (low-N) and normal nitrogen (normal-N) nutrition were examined. The leaf length and width were measured at 50, 60, and 70 days after transplanting. Leaves grown under low-N conditions were shorter and more narrow than those grown under normal-N conditions. The protein expression profiles of tobacco leaves harvested at 70 days after transplanting were analyzed by 2-dimensional electrophoresis, and five differentially expressed proteins including a putative protein were identified. Except for the MCM protein-like protein, the other three differentially expressed proteins of cyclophilin-like protein, vacuolar invertase INV2, MAR-binding protein and the one putative protein showed increased expression in the low-N nutrition group. Among these proteins, the cyclophilin-like protein, which is a stress-responsive signal protein, may play pivotal roles in regulating leaf development under stress conditions. Real-time quantitative PCR analysis showed that the mRNA expression level of the cyclophilin-like protein at day 50, 60 and 70 under low-N conditions was 0.90, 1.43 and 6.9-fold higher than that under normal-N conditions, indicating that the gene expression of cyclophilin-like protein was strongly induced by low-N conditions.

[Effects of light intensity on photosynthesis and dry matter production of flue-cured tobacco at its seedling stage].

Taking flue-cured tobacco Yunyan 87 as test material, this paper studied its photosynthesis and dry matter production at seedling stage under 100%, 88%, 72%, and 62% natural light intensities. At noon of sunny days, 100% natural light intensity inhibited the photosynthesis, while proper shading (88% natural light intensity) could eliminate the inhibition, and the daily photosynthesis was significantly higher than other treatments. Shading reduced the light saturation point and compensation point, enhanced the apparent quantum yield of photosynthesis and the net photosynthetic rate under weak light, increased the chlorophyll a and chlorophyll b contents, but decreased the chlorophyll a/b and cartenoids contents. Under 88% natural light intensity, tobacco seedlings had higher light saturation point, lower compensation point, higher suitability to the change of light intensity, and higher photosynthetic potentiality. 100% natural light intensity was more advantageous to the transfer of dry matter and soluble sugar to stem, while 88% natural light intensity was more beneficial to the transfer of dry matter and soluble sugar to root. Under the conditions of this experiment, proper shading (88% natural light intensity treatment) could improve the seedling quality of flue-cured tobacco.

[Identification of dominant and fragrance-enhancing microorganisms of tobacco leaves during ripening].

OBJECTIVE: We screened dominating microbial species isolated from aging flue-cured tobacco and studied their aroma improving effect. METHODS: Total DNA of microorganisms from the fermentation flue-cured tobacco surface of NC89, ZhongYan 100 and ZhongYan 101 were extracted. Under the PCR-DGGE, the diversity of microorganisms on fermentation tobacco leaves were studied and dominating microbial species were screened. We further studied the influence of dominating microbial species on the content of aroma components of the fermentation flue-cured tobacco. RESULTS: 1) By using DGGE analysis, there were 5 dominant bands A, B, C, D and E in all tobacco leaves samples of the three varieties; In further studies, five dominant DGGE bands were isolated, cloned and sequenced. From them we screened a dominant microorganism. 2) The content of most aroma components in tobacco leaves increased when they were sprayed with the dominant microorganism, comparing with the control. CONCLUSION: The dominant microorganism can improve the flavor of tobacco leaves during ripening.