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【Objective】 To explore the effects of new composite hydrogel on the physiological characteristics of tobacco seedlings under drought stress, and to provide theoretical basis for alleviating the toxicity of drought stress to tobacco. 【Method】 A total of 10 treatments including CK control and three different hydrogels added at 0.1%, 0.5% and 0.9% of soil dry mass: commercial hydrogel HS, new composite hydrogel HM (polyvinyl alcohol-acrylic acid-molecular sieve hydrogel) and HB (polyvinyl alcohol-acrylic acid-biochar hydrogel) were designed by pot experiment to study the effects of new composite hydrogels on tobacco under drought stress The effects of the new composite hydrogels on biomass accumulation, root development, photosynthetic system and oxidative stress of tobacco under drought stress were investigated. 【Result】 Under the same dosage conditions, HM and HB treatments were effective in increasing the fresh mass, dry mass and total water content of tobacco under drought stress compared to HS treatment. Compared with CK, HM and HB treatments could increase the fresh mass by a maximum of 153.91% and 126.34%, respectively. Under the same dosage conditions, HM and HB treatments significantly increased the total root length, total root surface area, average root diameter, root tip number and root volume, and improved the root vigor of tobacco compared with HS treatments; photosynthetic parameters and SPAD values of tobacco increased significantly and improved leaf stomatal status; SOD (superoxide dismutase), POD (peroxidase) and CAT (catalase) activities and soluble protein amounts of tobacco increased and MDA (malondialdehyde) amounts decreased significantly, which enhanced the resistance of tobacco. 【Conclusion】 Adding 0.9% HM and HB hydrogels to soil dry weight can effectively reduce the impact of drought stress on tobacco and improve tobacco drought resistance.

In response to the problems of slow detection speed, cumbersome operation, and solvent pollution in the detection of petroleum ether extract in tobacco leaves using the current traditional Soxhlet extraction method, low field nuclear magnetic resonance technology was used to detect the petroleum ether extract content in tobacco leaves. The detection parameters such as drying time, sample quality, echo time, and number of repeated scans were optimized to verify the repeatability and accuracy of the method, and the detection results were compared with the traditional Soxhlet extraction method. The results showed that 3. 0 g of tobacco leaf powder passing through a 40 mesh sieve was dried at 80 °C for 4 hours. Under the conditions of echo time of 0. 25 ms and 8 repeated scans, the petroleum ether extract detection results were good. The standard curve R2 reached 0. 999 81, and the relative standard deviation of repeatability was 1. 45% to 2. 99%. The intra day and inter day precision were 2. 61% and 1. 10%, respectively. The correlation coefficient between the detection results of this method and the Soxhlet extraction method reaches 0. 998 55, with an absolute error within 0. 02% ~ 0. 35% and a relative error within 0. 26%~3. 69%. Compared with the traditional Soxhlet extraction method, this method is simple, fast, accurate, and solvent free, making it suitable for the accurate quantification of petroleum ether extracts from large quantities of flue-cered tobacco leaves. [ABSTRACT FROM AUTHOR]

A reversed-phase high performance liquid chromatographic (RP-HPLC) method for the determination of carotenoids in flue-cured tobacco leaves was developed. Carotenoids were extracted from flue-cured tobacco leaves by acetone-water (90:10, v/v) solution containing 0.1% butylated hydroxytoluene (BHT). Plant proteins were eliminated by adding 0.1 g Pb(Ac)2 and by centrifugation (10000 r/min) for 5 min at 4 degrees C. Lutein, beta-carotene, neoxanthin, violaxanthin and other plant pigments were separated on a reversed-phase C18 column (3.9 mm i.d. x 150 mm, 5 microm), with a mobile phase of (A) methanol-isopropyl alcohol (1:1, v/v) and (B) water using a gradient elution at a flow rate of 0.5 mL/min. The optimum elution gradient was as follows: 0-10 min, 70% A + 30% B; 10-17 min, 100% A; 17-30 min, 90% A + 10% B. The recoveries of carotenoids in flue-cured tobacco leaves were 91.77%-97.42%, and relative standard deviations were 3. 46%-0.98%. This method was applied to determine carotenoids in flue-cured tobacco leaves during its growth with satisfactory results.