Solanaceae tobacco belongs to panicum miliaceum. Leaves contain nicotine, which is used to make cigarettes, cigars, hookahs, chewing tobacco and snuff after harvest. It is a hobby industrial raw material crop cultivated all over the world.
There are about 60 kinds of tobacco, most of which are wild. There are widely cultivated species in China. One is common tobacco (N.tobacum), also known as safflower tobacco, which is used in world commodity production; One is N.rustica, which is widely cultivated in the Soviet Union and India, and a small amount is also cultivated in China, Xinjiang and Gansu. Both of them are native to South America, and their original wild species are distributed in the Andes from Ecuador and Bolivia to Argentina. Both are naturally occurring diploids. Ordinary tobacco also forms many types because of different modulation methods, provenances, regions, cultivation measures and use requirements: flue-cured tobacco, indoor drying tobacco leaves with fire pipes, yellow bright tobacco with leaf color, also known as Virginia type; Burley tobacco type is a kind of dry tobacco with milky stems and leaves; Maryland tobacco is a kind of air-cured tobacco originated in Maryland, USA. Cigar type is a kind of air-dried cigarette used to make cigars; Smoked tobacco is a kind of tobacco smoked indoors by using the heat of smoldering fire and the thick smoke produced by smoldering fire; Oriental tobacco is a kind of sun-cured tobacco with special fragrance and small leaves, also known as Turkish tobacco or oriental tobacco; Sun-cured tobacco is the sun-cured tobacco that browns the pleated tobacco leaves; Sun-cured tobacco is a combination of sun exposure and baking, which modulates tobacco leaves on cigarette folds or racks into bright yellow, brown yellow or red yellow sun-cured tobacco. Each type has many cultivated varieties. In addition, there are N.alata and N.□lauca for viewing.
The historical and distributed relief of a temple in palenque, Mexico, which was built in 432 AD, shows the scene of Mayan priests blowing cigarettes with their pipes during the ceremony (Figure 1), which is the earliest evidence of human utilization of tobacco. Tobacco and pipes left by cave-dwelling Indians about 650 years ago were found in northern Arizona, USA. Indians in the Caribbean called tobacco Tobago, hence the English name. 15 19, tobacco was planted in Yucatan Peninsula, Mexico. 153 1 year, the Spanish planted tobacco in Haiti and the West Indies, and then spread to Portugal and Spain. At that time, J. Nico, the French ambassador to Portugal, gave tobacco seeds to the French king. Later, it gradually spread to various countries. Linnaeus named it Nick in memory of Nico.
Morphological characteristics The main roots of common tobacco are not obvious, and lateral roots and adventitious roots are the main components of the root system. Root system can synthesize nicotine, and root tip activity has a great relationship with nicotine content. The plant height is 1 ~ 3m. The stem is erect, with axillary buds in each axil, which can germinate into branches. Leaves alternate and spirally arranged. After transplanting, the leaves of tobacco plants grow rapidly, and the peak time is about 45 days after transplanting, with an increase of about 1 leaf per day. Most common tobacco varieties have no petiole, and the joint between leaf base and stem is spike-shaped, commonly known as leaf spike. The leaf area index of most flue-cured tobacco varieties is about 0.65. The shapes of leaves are oval, oblong, oval, oblong, lanceolate and heart-shaped. The leaves are all green except burley tobacco. Conical cyme, calyx bell-shaped, corolla tubular funnel-shaped, composed of 5 petals, most of which are pink. Self-pollination, but the natural hybridization rate is high, often exceeding 4%. Generally, it takes 45 ~ 60 days for flue-cured tobacco varieties from transplanting to budding, and 7 ~ 10 days from budding to flowering. The number of flowers in the daytime accounts for about 80% of the total number of flowers in the whole day, and there are almost no flowers in Rosty Yi from 9: 00 to 4: 00 at night. It takes about 1 month from flowering to fruit ripening. Capsule ovoid, calyx persistent. Generally, it contains 2000 ~ 3000 seeds. The seeds are small, light brown to dark brown, with uneven reticular patterns on the surface and irregular shapes. There are about 65,438+00,000 ~ 65,438+05,000 seeds per gram (Figure 2).
The plant height of Huanghua tobacco is not as high as that of ordinary tobacco, and its lignification is poor. The leaves are heart-shaped, the leaf length is 1 ~ 1.5 times as wide, the base is widest, the leaf base is depressed near the midvein, the leaf quality is thick and heavy, and the petiole is obvious. The color is light yellow to slightly green. The seeds are slightly larger than ordinary tobacco.
Tobacco leaves, stems, calyxes and fruits all have multicellular hairs. Among them, glandular hair cells contain chlorophyll, which can synthesize secretions containing gum and resin. There is a certain relationship between glandular hair and the aroma of tobacco.
Tobacco likes temperature, light, drought, waterlogging and barren, and needs more potassium. New shoots can grow at 8 ~ 38℃, and the optimum temperature is 25 ~ 28℃. The lowest temperature that roots can tolerate is 7℃, the highest temperature is 43℃, and the optimum temperature is about 365438 0℃. Generally speaking, the average daily temperature of flue-cured tobacco leaves at maturity is 20 ~ 25℃. The average temperature of sun-cured tobacco and burley tobacco should be 65438 08℃, and the duration should be more than 90 days. Yellow-flowered tobacco is more resistant to cold climate, especially at maturity. Under the condition of sufficient but not strong sunshine, the quality of tobacco leaves is excellent.
The influence of precipitation on tobacco mainly depends on whether the rainfall is evenly distributed. The average monthly rainfall during the growing period is 100 ~ 130mm. Soil has a great influence on the quality of tobacco leaves, and different types and uses of tobacco have different requirements for soil. Sun-cured red tobacco is suitable for soils with high viscosity and high organic matter; Burley tobacco needs fertile soil with high nitrogen content; Oriental tobacco is suitable for planting in sandy land with low organic matter content, low fertility, thick topsoil and few stones. Loam and sandy clay with loose texture and good structure are suitable for planting flue-cured tobacco. Organic matter content 1 ~ 2%, available nitrogen 40 ~ 60 ppm, available phosphorus about 25ppm, and available potassium 100ppm or more are required. The soil salt content is less than 0.06%, the chlorine content is less than 35ppm, and the pH value is between 5.5 and 7.0.
Tobacco is a good precursor of cereal crops in cultivation and management rotation. Wheat, rice and rape are planted in tobacco stubble and generally grow well. Cultivation management mainly includes the following links:
Seedling transplanting in China, except for some areas where there are yellow-flowered tobacco and sun-cured tobacco, most of them are seedling transplanting. The seedbed area is about 5 ~ 7% of the field planting area. Because of the different climates, some plants are brewed or heated in hotbeds, some plants are raised in greenhouses, and some plants are raised in cold beds covered with plastic films, gauze, glass or other coverings. Seedbed soil should be disinfected by steam, chemicals or fumigation to prevent diseases, insects, weeds and nematodes. The selected seeds must be disinfected with chemicals, washed and dried with clear water, and sown or germinated in time. Generally, 4 ~ 5g seeds are used per 10 square meter. The sowing date varies with the tobacco in spring, summer and winter and different regions. After sowing, cover with a thin layer of fine sand, plant ash, mule dung, straw or pine needles.
The first 12 hour of seed germination is the physical water absorption stage; The next 24 ~ 36 hours is the photosensitive stage, when light can promote germination to a certain extent; Then enter the growth stage. The optimum temperature for tobacco seed germination is 24 ~ 29℃, the lowest temperature is 7 ~ 10℃, and the highest temperature is 35℃. The optimum temperature of seedbed is 25 ~ 30℃. Generally, the seedling spacing is 6 ~ 8 cm twice. Measures such as cutting off water, uncovering cover or pinching leaves in the middle and late stage of seedling raising can make tobacco seedlings grow in a balanced way and improve their stress resistance. When the air temperature is stable at 12 ~ 13℃ and the ground temperature is above 9℃, it can be transplanted. If you use double-row or four-row transplanter to transplant rice, you can finish digging holes (ditching), planting seedlings, watering and covering soil at one time. Planting density varies with tobacco type, topography and soil. China generally plants 1300 ~ 1800 plants per mu.
In the field management after tobacco transplanting, it is necessary to water, fertilize, intertillage, cultivate soil and control pests and diseases in time. Fertilizer has a great influence on the quality of tobacco leaves. Nitrogen deficiency in soil leads to small tobacco leaves, low weight per unit area and thin and light leaves after baking; Excessive nitrogen fertilizer makes the tobacco leaves loose and rough, and the cured tobacco leaves are spicy, green-brown or nearly black, and the quality decreases. When phosphorus fertilizer is insufficient, the tobacco plants grow slowly, the leaves are long, narrow and dark green, and they are dull after baking; Too much paint will cause prominent lines, rough texture, less oil and easy to break. Potassium is the main component of tobacco ash. When properly applied, the leaves are smooth, fragrant and combustible. If it is insufficient, the blade will be rough and wrinkled, the tissue at the tip and edge will stop growing, forming dead spots and holes, the blade will break and the combustion will be poor. The content of chlorine in soil is the limiting factor of tobacco planting. When the chlorine content in tobacco leaves is higher than 1%, the burning speed of tobacco leaves begins to slow down, and 1.5% is the critical line. When it exceeds 2%, the black ash will go out. Proper fertilization, timely transplanting, timely watering and drainage can promote the robust growth of tobacco plants and avoid the phenomenon of "early flowering" when tobacco plants do not reach a certain height and number of leaves. At the same time, proper planting density, timely watering, drainage and disease control should be carried out to prevent drought, waterlogging, field closure and the "sun-drying" phenomenon that the lower leaves of tobacco plants turn yellow or even wither before reaching normal maturity.
Topping is one of the main measures to promote high quality and high yield. Except for oriental tobacco, it must be done at the right time. Generally, the inflorescence is picked at the time of budding, so as to facilitate the spreading of the upper leaves, and the axillary buds are erased in time to prevent the growth of lateral branches (branches), once every 5 days or so. Now, it can be carried out with the air flow automatic topping device. A sprayer is installed behind the topping machine, and a bifurcation inhibitor, such as fatty alcohol, is sprayed on the tobacco stem at the same time of topping to inhibit the growth of axillary buds. (See colorful tobacco fields and ordinary tobacco)
50 ~ 60 days after ripening, harvesting and transplanting, tobacco leaves gradually mature from bottom to top. When the leaves stop growing, the tissues are gradually enriched, and the dry matter accumulation in the leaves reaches the maximum, the technology is mature and can be harvested. The maturity of tobacco leaves is characterized by the change of leaf color from green to yellow-green, the main veins are white and yellow, the base is crisp, the leaves are hairy, the leaves are shiny, and the tip and edge of the leaves are slightly drooping. Using plant growth regulators in production can shorten the maturity of tobacco leaves and make them yellow evenly. European and American countries use whole plant cutting method or leaf picking method when harvesting, and also use harvester to harvest. Flue-cured tobacco and most sun-cured tobacco in China are picked manually, usually 3-9 times, and some are harvested in sections or once.
Breeding The goal of tobacco breeding is to breed varieties with high quality, high yield and strong stress resistance (disease resistance, drought tolerance, fertilizer tolerance, etc.). ). Systematic breeding, hybrid breeding and haploid breeding are generally used to cultivate new varieties, and protoplast culture and cell fusion breeding are also applied. Tobacco haploid breeding can shorten the time of cultivating new varieties. Haploid breeding was first successful in tobacco in 1970s. In China, Shanyu 1, Wanyan 1 and other varieties were selected by haploid breeding. In addition, some wild species of Nicotiana were interbred with common tobacco, and the disease and insect resistance genes of wild species were transferred to excellent cultivated varieties of common tobacco, thus many new varieties resistant to single or multiple diseases were cultivated. The excellent disease-resistant varieties now popularized in China are Honghuadajinyuan, Changbohuang, Yongding 1, NC82 and Spit G-28.
Tobacco, the main pest, may be attacked by various diseases, insects and weeds at any time from germination to leaf maturity, from material preparation to storage. Especially the most serious condition. Many abiotic diseases are related to climate, for example, cold will lead to the chlorosis of seedling leaves and frostbite of tobacco plants; Storm impact can cause reddish-brown rain spots on the back of blades; Hail will tear leaves and hurt tobacco stems; Lightning strike can make the leaves twist and fold, and the pulp tissue is disc-shaped layer; Drought can make leaves form brown and yellow spots; The back of leaves is often blown by the wind and burned by the sun, which can produce amorphous dead zones; Air pollution can lead to climate spots and so on. In addition, because tobacco is sensitive to excessive and insufficient nutrients, element deficiency of nitrogen, phosphorus, potassium, magnesium, calcium, boron and chlorine or polyoxin's disease often occurs.
Parasitic diseases can be divided into: ① bacterial diseases. For example, angular leaf spot can form polygons and dark brown spots of different sizes on leaves; Bacterial wilt can make tobacco plants wither rapidly, but the leaves remain green, black stripes appear on one side of the stem, and the vascular bundles turn yellow-brown or black-brown. ② Mycosis. For example, the symptoms of black shank disease are brown roots, wilting leaves, black stems and upturned stems, brown pith shrinking into a disc shape, large round spots on leaves, and even death of the whole plant in severe cases. Brown spots or black spots form lesions in the middle of leaves, pedicels and capsules, and concentric rings often appear in the dead tissues of lesions. ③ Viral diseases. Tobacco common mosaic virus disease and tobacco cucumber mosaic virus disease are the most harmful diseases in China, both of which form dark green and light green leaves, even dwarf tobacco plants, and can infect tobacco plants together. In addition, potato virus often causes harm; Tobacco leaf curl virus was also found. ④ Other parasitic diseases. There are mainly root-knot nematodiasis caused by root-knot nematodes and seed plants parasitic on tobacco, such as Luodang.
The main pests invading tobacco are tobacco aphid, tobacco moth, tobacco leaf miner, Spodoptera litura and tobacco moth.
Modulation is the primary processing of mature tobacco leaves, which makes the fresh leaves with water content of about 85% dry. A series of changes in chemical composition are beneficial to the quality, and the color, aroma and taste required by various tobaccos are fixed, which is suitable for tobacco industry. According to different types of tobacco, there are mainly the following different modulation methods.
Flue-cured tobacco leaves are tied on bamboo (wood) poles or ropes and hung in special curing barn for artificial heating. According to the change of tobacco color and dryness, it can be divided into three stages: ① yellowing stage. The temperature gradually increased from 35℃ to 42 ~ 45℃, and the relative humidity gradually decreased from about 95% to about 70%. Under these conditions, due to a certain degree of water deficit in the early tobacco leaves, the activity of intracellular hydrolase was enhanced, and carbohydrates (mainly starch) and protein were decomposed into reducing sugar and soluble nitrogen compounds, which was beneficial to the quality. Chlorophyll mostly decomposes and disappears; Carotenoids and lutein are only partially destroyed, because their colors are no longer covered by the green of chlorophyll, but appear bright yellow. The degradation products of carotenoids include dozens of cyclocitral and so on. Although the content in tobacco is very small, it plays an important role in the aroma of tobacco leaves. ② Fixing color period. From the end of yellowing, the temperature gradually increased to 55℃, with an average temperature increase of about 0.5℃ every 1 ~ 2 hours, and the relative humidity gradually decreased to about 30% (the wet bulb temperature was stable at 38 ~ 39℃), which made the leaves gradually dehydrated, dried, yellowed and fixed. ③ Dry tendon period. Tobacco leaves have passed the fixation period, and some main veins are not dry. At this time, the temperature can be increased by 2 ~ 3℃ every hour until it reaches about 70℃, and the relative humidity can be reduced to about 65438 05% (the wet bulb temperature should not exceed 43℃). When the main vein is completely dry, the maintenance can be completed. The whole baking process takes 3 ~ 5 days.
Flue-cured tobacco is usually heated by fire tube, and the flue-cured barn is naturally ventilated when the airflow rises. The plane temperature in the curing barn should be uniform. The openings of ventilation and dehumidification air inlet tunnel and exhaust window can be adjusted according to the quantity of tobacco in curing barn, the moisture content of tobacco leaves, the climatic conditions in curing season and the changes of tobacco leaves during curing. In addition, there are tunnel continuous curing barn, dense curing barn with gas or liquid as fuel, and stacked curing barn with automatic temperature control and humidity control.
Air-curing is a modulation method of hanging tobacco leaves in the air-drying room to complete withering, discoloration and drying. Burley tobacco is made in this way. The optimum air drying temperature is 25 ~ 35℃; The optimum relative humidity is 70 ~ 75% during the day and 90 ~ 95% at night. The change of leaves in wilting and yellowing stage is similar to that of flue-cured tobacco, but the sugar content of leaves after air-drying is very low because of the long air-drying time. In the drying stage after yellowing, the leaves are still in the state of alternating dry days and wet nights, and the color of tobacco leaves becomes darker, which has an important influence on the formation of the unique aroma and taste of burley tobacco. Burley tobacco can also be dried after the waist leaves are ripe, which takes a long time but saves effort.
Sun curing is the use of sunlight to modulate tobacco leaves. According to different drying tools, it can be divided into cable drying and folding drying. The "green smoke" in Huanghua tobacco leaves is the whole plant exposed to the field after harvest. Chlorophyll is not completely decomposed due to rapid water loss, and it is green after drying; If it is left in the field after ripening, chlorophyll will decompose, and it will be "yellow smoke" in yellow smoke after drying. After the yellow smoke changes color, it can be quickly dried and fixed by exposure. The quality of light-colored sun-cured yellow tobacco is similar to that of flue-cured tobacco; Dark yellow smoke is between light yellow smoke and red smoke. Sun-cured red tobacco can promote the changes of polyphenols, oxidized amino acids and sugars in tobacco leaves by absorbing night dew in the drying stage. The modulated tobacco leaves are brownish yellow in color, mellow in smoke and strong in physiological intensity.
The grading of graded tobacco leaves mainly depends on the quality factors such as the position and color of tobacco leaves. According to the unified national standards, flue-cured tobacco in China is divided into three groups: middle and lower yellow, upper yellow and bluish yellow, and then graded according to quality factors (oil content, texture, luster, color, damage, etc.). At present, the grading standards of sun-cured red cigarettes are mostly local standards. Every tobacco-producing country in the world has its own tobacco grading standards. The basis for formulating standards in different countries is basically the same, but the number of grades is different.
Uses Tobacco leaves are the basic raw materials for making tobacco products. There are many kinds of cigarettes with different tastes: ① cigarettes. There are three types of cigarettes. The raw materials of flue-cured tobacco are almost all flue-cured tobacco leaves, and the cut tobacco is light in color, with flue-cured tobacco aroma and moderate in intensity; Mixed cigarettes are mainly flue-cured tobacco, burley tobacco and oriental tobacco, and are mixed with other sun-cured tobacco. Cut tobacco is dark in color, with mixed aroma of various types of tobacco leaves, and rich. All or most of the raw materials of sun-cured tobacco are sun-cured tobacco, which has the aroma of sun-cured tobacco and is rich. Two cigars. Cigar core leaves, bundled leaves and wrapped leaves are used as raw materials and made by machine or hand. There are two kinds of sharp leaves and round heads, and the aroma is rich and rich. ③ Pisi cigarettes (hookah). Sun-dried tobacco leaves are used as the main raw materials, and smoked with hookah, bamboo hookah or dry hookah, with rich fragrance and strong vigor (Figure 3: Bamboo hookah and China hookah). 4 dou cigarettes. Taking sun-cured tobacco and air-cured tobacco as the main raw materials, it is made into particles, small pieces or filaments, which are smoked with a pipe, with rich aroma and full of vigor. 5 snuff. Take sun-cured tobacco as the main raw material, grind it into powder, and apply it directly to the nostrils to smell. 6. Chew cigarettes. Taking air-dried tobacco leaves as the main raw material, it is made into cakes, cakes, strips or pills, which are chewed in the mouth, and the fragrance is slightly sweet, and some are salty. Medicinal cigarettes developed in recent years are made by mixing Chinese herbal medicines into cigarettes. It has certain curative effect on some diseases such as chronic bronchitis in the elderly. Nicotine extracted from tobacco stems and tobacco stems can be used as pesticides. Tobacco stem fiber can be used as raw material for papermaking and pressed fiberboard. Seed oil can be used as coating and oil cake can be used as feed or fertilizer. Tobacco leaves contain edible soluble protein, which becomes colorless and tasteless crystals after purification, and its extraction amount can reach more than 6% of tobacco leaf output, which may become a potential food with rich nutrition. The residue after protein extraction can be pulped into cigarette flakes and used as filler for low tar cigarettes.
Tobacco is harmful to human health, and smoking has been opposed and restricted for a long time. As early as 1535, General History of India considered smoking a "bad habit". Smoking was first banned in Britain. Japan banned smoking in 16 15, burned tobacco leaves and pulled out tobacco plants in the field. Smoking was also banned in Chongzhen of Ming Dynasty in China, and offenders were punished by flogging. 1954 and 1964, the Royal British Medical Association and the US Department of Health successively published reports on the health hazards of smoking, which triggered a lasting anti-smoking climax. At that time, cigarette sales declined. In recent 20 years, 4500 ~ 5000 components have been identified from flue gas. About 0.6% of smoke particles are related to cancer, of which 0.2% are cancer inducers, mostly polycyclic aromatic hydrocarbons, heterocyclic aromatic hydrocarbons and lipid compounds. Another 0.4% is the precursor of cancer, mostly tetracyclic aromatic hydrocarbons, pentacyclic aromatic hydrocarbons, phenols, substituted phenols, nitrosamines and nornicotine. Reducing the harmful components of tobacco and tobacco products to human health is an important task of tobacco research. Because most of the harmful components in smoke are contained in smoke tar. Therefore, reducing the tar content in cigarettes has attracted people's attention.