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Comparison of appearance of flue-cured tobacco after curing with different salicylic acid concentrations.
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Salicylic acid (SA) can induce plants to actively enhance abiotic stress resistance. Spraying SA to prevent cold stress in flue-cured tobacco fields can provide theoretical support and practical guidance for the actual protection from cold stress in fields at high altitude in Yunnan. The experiment was performed in Jianchuan County Yunnan Province,...
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... The AC of cigar tobacco leaves refers to the process of gradually drying fresh tobacco leaves under natural or controlled temperature, OPEN ACCESS EDITED BY humidity, and ventilation conditions, causing changes in the internal substances of the leaves to achieve the desired quality. Therefore, the AC of cigar tobacco leaves is not simply a matter of drying the leaves but involves delicate coordination between the chemical composition of the leaves and drying speed (Salehzade et al., 2009;He et al., 2020). The entire AC process can be divided into four distinct stages: wilting, yellowing, browning, and stemdrying. ...
Introduction
Air curing (AC) plays a crucial role in cigar tobacco leaf production. The AC environment is relatively mild, contributing to a diverse microbiome. Fungi are important components of the tobacco and environmental microbiota. However, our understanding of the composition and function of fungal communities in AC remains limited.
Methods
In this study, changes in the chemical constituents and fungal community composition of cigar tobacco leaves during AC were evaluated using flow analysis and high-throughput sequencing.
Results
The moisture, water-soluble sugar, starch, total nitrogen, and protein contents of tobacco leaves exhibited decreasing trends, whereas nicotine showed an initial increase, followed by a decline. As determined by high-throughput sequencing, fungal taxa differed among all stages of AC. Functional prediction showed that saprophytic fungi were the most prevalent type during the AC process and that the chemical composition of tobacco leaves is significantly correlated with saprophytic fungi.
Conclusion
This study provides a deeper understanding of the dynamic changes in fungal communities during the AC process in cigar tobacco leaves and offers theoretical guidance for the application of microorganisms during the AC process.
... This technique is highly efficient, convenient and provides a viable method for examining tobacco aroma substances [19,20]. Consistent with previous findings [21][22][23][24], this study revealed a substantial rise in the levels of chlorogenic acid and total polyphenols after flue-curing (as shown in Figure 4), which contributes to the mild, sweet flavor and scent of flue-cured tobacco products. It has been further confirmed that the increase in polyphenol content is due to the pyrolytic conversion of pyrolysates such as lignin and cellulose in tobacco leaves during the curing process [8]. ...
The composition and content of aroma substances in flue-cured tobacco (Nicotiana tabacum L.) will affect the quality of tobacco. To investigate the correlation between various aroma substances of K326 before and after flue-curing, and their impact on tobacco quality and diversity, this study employed the middle leaves of K326 and KRK26 as test materials. Samples were collected both before and after flue-curing for untargeted metabolomics analysis. The results of K326 showed that 584 metabolites were significantly different and there were 44 aroma-related metabolites, including alcohols, aldehydes, phenols, organic acids, etc. The analyzed aroma compounds consist of 37 known tobacco aroma substances, while 7 metabolites, previously not associated with tobacco aroma, have been identified as aroma substances in other food products. These findings suggest that these seven metabolites might may be potential tobacco aroma compounds. Further analysis showed that the content of phenols, alcohols, and aldehydes increased significantly after flue-curing, but the content of organic acids decreased. Furthermore, the analysis of KRK26 revealed a correlation between the quantity of aroma substances and the type of tobacco. These findings serve as a reference for enhancing the flue-curing process of K326 and optimizing the industrial production of cigarettes that use cured K326 tobacco leaves.
... The exogenous brassinolactone application effectively relieves the cold stress on the physiological metabolism of rice at the booting stage and improves yield (Wang S. et al., 2020). Salicylic acid (SA) alleviates chilling stress by improving the quality of fresh tobacco leaves, the enzyme activity of the antioxidant system, and the quality of tobacco leaves (He et al., 2020). Nevertheless, the role of Mg under cold stress to improve crop growth, yield, and quality has been neglected or not fully elucidated. ...
Cold stress is one of the major constraints limiting the productivity of many important crops, including tobacco (Nicotiana tabacum L.) production and quality worldwide. However, the role of magnesium (Mg) nutrition in plants has been frequently overlooked, especially under cold stress, and Mg deficiency adversely affects plant growth and development. Here, we evaluated the influence of Mg under cold stress on tobacco morphology, nutrient uptake, photosynthetic and quality attributes. The tobacco plants were grown under different levels of cold stress, i.e., 8°C, 12°C, 16°C, including with a controlled temperature of 25°C, and evaluated their effects with Mg (+Mg) and without Mg (–Mg) application. Cold stress resulted in reduced plant growth. However, the +Mg alleviated the cold stress and significantly increased the plant biomass on an average of 17.8% for shoot fresh weight, 20.9% for root fresh weight, 15.7% for shoot dry weight, and 15.5% for root dry weight. Similarly, the nutrients uptake also increased on average for shoot-N (28.7%), root-N (22.4%), shoot-P (46.9%), root-P (7.2%), shoot-K (5.4%), root-K (28.9%), shoot-Mg (191.4%), root-Mg (187.2%) under cold stress with +Mg compared to –Mg. Mg application significantly boosted the photosynthetic activity (Pn 24.6%) and increased the chlorophyll contents (Chl-a (18.8%), Chl-b (25%), carotenoids (22.2%)) in the leaves under cold stress in comparison with –Mg treatment. Meanwhile, Mg application also improved the quality of tobacco, including starch and sucrose contents, on an average of 18.3% and 20.8%, respectively, compared to –Mg. The principal component analysis revealed that tobacco performance was optimum under +Mg treatment at 16°C. This study confirms that Mg application alleviates cold stress and substantially improves tobacco morphological indices, nutrient absorption, photosynthetic traits, and quality attributes. In short, the current findings suggest that Mg application may alleviate cold stress and improve tobacco growth and quality.
... According to the relevant research reports, in Yunnan, the largest growing area in China, low-temperature chilling injury causes serious damage to the tobacco growers. In the subsequent tobacco flue-curing process, it can also increases the brown reaction, which leads to a significant reduction in the apparent quality and taste, and causes huge economic losses 5,6 . Therefore, it has become the flash point and focus of tobacco abiotic stress research to study the physiological response mechanism of tobacco to low temperature stress, so as to reduce yield loss caused by cold injury. ...
Tobacco is be sensitively affected by chilling injury in the vigorous growth period, which can easily lead to tobacco leaf browning during flue-curing and quality loss, however, the physiological response of tobacco in the prosperous period under low temperature stress is unclear. The physiological response parameters of two tobacco varieties to low temperature stress were determined. The main results were as follows: ① For tobacco in the vigorous growing period subjected to low-temperature stress at 4–16 °C, the tissue structure of chloroplast changed and photosynthetic pigments significantly decreased compared with each control with the increase of intensity of low-temperature stress. ② For tobacco in the vigorous growing period at 10–16 °C, antioxidant capacity of the protective enzyme system, osmotic adjustment capacity of the osmotic adjusting system and polyphenol metabolism in plants gradually increased due to induction of low temperature with the increase of intensity of low-temperature stress. ③ Under low-temperature stress at 4 °C, the protective enzyme system, osmotic adjusting system and polyphenol metabolism of the plants played an insignificant role in stress tolerance, which cannot be constantly enhanced based on low-temperature resistance at 10 °C. This study confirmed that under the temperature stress of 10–16 °C, the self-regulation ability of tobacco will be enhanced with the deepening of low temperature stress, but there is a critical temperature between 4 and 10 °C. The self-regulation ability of plants under low temperature stress will be inhibited.
... According to the results of local field cold stress investigation, there was a significant drop temperature accompanied rainfall and a little hail occurred on 16 and 17 August. In the next days, tobacco showed a range of symptoms caused by cold stress [15]. The surface color of the tobacco leaves changed from normal to dark green, purple red, then dark red, and finally off-white [15]. ...
... In the next days, tobacco showed a range of symptoms caused by cold stress [15]. The surface color of the tobacco leaves changed from normal to dark green, purple red, then dark red, and finally off-white [15]. Finally, there was a large area of scalded leaves appeared, showing poor flue-curing availability and poor quality of flue-cured tobacco leaves. ...
... The temperature dropped by 25.4°C at the experiment site on the day subjected to cold stress. Within the subsequent 6 days, the appearance and color of middle and upper tobacco leaves changed suddenly, turning from green to off-white [15], which was attributed to evidence from existing research that suggest cold stress can damage the photosynthetic system of plant leaves to reduce the content of chloroplast pigments [17]. Additionally, the high altitude also led to significant increase in ultraviolet irradiation, which probably contributed to damage of the photosynthetic system after cold stress [18]. ...
Background
Weather change in high-altitude areas subjects mature tobacco ( Nicotiana tabacum L.) to cold stress, which damages tobacco leaf yield and quality. A brupt diurnal temperature differences (the daily temperature dropping more than 20 °C) along with rainfall in tobacco-growing areas at an altitude above 2450 m, caused cold stress to field-grown tobacco.
Results
After the flue-cured tobacco suffered cold stress in the field, the surface color of tobacco leaves changed and obvious large browning areas were appeared, and the curing availability was extremely poor. Further research found the quality of fresh tobacco leaves, the content of key chemical components, and the production quality were greatly reduced by cold stress. We hypothesize that cold stress in high altitude environments destroyed the antioxidant enzyme system of mature flue-cured tobacco. Therefore, the quality of fresh tobacco leaves, the content of key chemical components, and the production quality were greatly reduced by cold stress.
Conclusion
This study confirmed that cold stress in high-altitude tobacco areas was the main reason for the browning of tobacco leaves during the tobacco curing process. This adverse environment seriously damaged the quality of tobacco leaves, but can be mitigated by pay attention to the weather forecast and pick tobacco leaves in advance.
Cigar variety CX-010 tobacco leaves would produce localized green spots during the air-curing period, and spraying exogenous sucrose could effectively alleviate the occurrence of the green spots. To investigate the alleviation effect and physiological mechanism of exogenous sucrose treatment, the total water content of tobacco leaves was measured in different sucrose treatments during the air-curing period, as well as the number and size of green spots, and non-targeted liquid chromatography-mass spectrometry (LC-MS) metabolomics analysis was performed with the tobacco leaves of T3 (0.4 mol/L sucrose) and control (CK, without spraying) treatments at different air-curing stages. The results showed that, in the early air-curing stage, the total water content of tobacco leaves showed a trend of T3 (0.4 mol/L sucrose) < CK < T2 (0.2 mol/L sucrose) < T1 (0.1 mol/L sucrose), and the number and size of green spots showed a trend of T3 < T2 < T1 < CK. 259 and 178 significantly differentially expressed metabolites (DEMs) between T3 and CK-treated tobacco leaves were identified in the early air-curing and the end of air-curing, respectively, which mainly included lipid and lipid-like molecules, carbohydrates, as well as organic acids and their derivatives. Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, it was found that DEMs were significantly enriched in 9 pathways, including tryptophan metabolism and tyrosine metabolism, at the early air-curing stage and 7 pathways, including benzoxazinoid biosynthesis and arginine biosynthesis, at the end of air-curing. The exogenous sucrose treatment significantly altered abundance as well as metabolic pathways in tobacco leaves, and most of the significantly altered KEGG metabolic pathways and associated differential metabolites were related to resistance to stress, which may play a key role in alleviating the appearance of green spots.
Cold stress has a significant effect on plant physiology inducing growth hindrance and reduced yields. This study was aimed to evaluate the effect of mammalian sex hormones (progesterone and β-estradiol), abscisic acid (ABA), and salicylic acid (SA) on plant growth, chlorophyll, malondialdehyde (MDA), hydrogen peroxide (H2 O2) and the activities of anti-oxidative and nitrate assimilation enzymes in common bean (Phaseolus vulgaris L.) seedlings under cold stress. For this purpose, cold stress was conducted to 11-day-old seedlings in a climate chamber at 9/5°C (day/night), but for control, the temperature was set at 25/20°C (day/night). Progesterone (Pro) 10⁻⁹ M, β-oestradiol (ES) 10⁻⁶ M, ABA 10⁻⁴ M, and SA 10⁻⁴ M were applied to 11-day-old seedlings using a handheld sprayer. The results of this experiment showed that cold stress significantly decreased plant growth, and it was followed by an increase in MDA and H2 O2 content in common bean seedlings. However, the exogenous application of Pro, ES, ABA, and SA mitigated the adverse effect of cold stress in common bean seedlings. In this respect, cold stress decreased the activities of nitrate reductase (NR), nitrite reductase (NiR), and glutamine synthetase (GS) by 41.03%, 35.20%, and 47.54%, respectively, compared to control. However, under cold stress, Pro, ES, ABA, and SA treatments significantly increased NR, NiR, and GS activities by 41.87%, 14.80%, 33.87%, and 64.82 % for NR, 3.4%, 30.10%, 12.75%, and 33.12% for NiR, and 83.00%, 50.10%, 83.14%, and 9.34% for GS, respectively, compared to the plants treated with cold stress. These results suggest that exogenous application of Pro 10⁻⁹ M, ES 10⁻⁶ M, ABA 10⁻⁴ M, and SA 10⁻⁴ M after three days mitigate the unfavourable impact of cold stress in common bean seedlings by enhancing nitrate metabolism and antioxidant enzyme activities; their spraying on the leaves is beneficial for plant recovery and growth under cold stress. © 2022, Lithuanian Research Centre for Agriculture and Forestry; Vytautas Magnus University. All rights reserved.
