Some Physical Characteristics Of Tobacco Raw Material Type Virginia Grown In Republic Of Srpska Production Area

Transcription

1 UDC: (497.6) ID: Original research paper Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Some Physical Characteristics Of Tobacco Raw Material Type Virginia Grown In Republic Of Srpska Production Area Obrenija Kalamanda Tobacco Factory Banja Luka, Republic of Srbska Valentina Pelivanovska Tobacco Institute - Prilep,Republic of Macedonia Abstract: The aim of research was to determine major physical properties of Virginia tobacco varieties DH-17 and Hewessi-17, grown in two different localities in the region of Republic of Srpska. Investigations were carried out in , during three growing seasons (May - September). Dry tobacco leaf samples from the lower, middle and upper stalk belts were used in the investigation. According to the obtained results, the variety DH-17 had better yield output as compared to Hewessi-17. Physical indexes of quality (length, width, thickness and midrib content in the total mass of leaf tissue) were better in Hewessi-17. Exception from this was leaf tissue substantiality, which was higher in D-17 than in Hewessi-17, as was confirmed by the number of cigarettes produced from 1 kg of tobacco. Based on investigations of Virginia tobaccos grown in the region of Republic of Srpska, the variety DH-17 has higher value of usability compared to Hewessi-17. Key words: tobacco, Virginia, growing period, insertion, physical properties, quality. Received: / Accepted:

2 70 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Introduction Tobacco, being consumer item, represents original vegetative material of its kind. It is obvious that no other vegetative product has not influenced political, economic, social and religious life of all nations and people in such a great extent, due to which fact they have always expressed enormous interest in production, trade, industrial procession and, of course, in using tobacco. Virginia is a type of tobacco with big leaves of great significance in modern production of cigarettes. Virginia tobacco type becomes ever demanding tobacco raw material worldwide and nationally. Production of this type of tobacco is of newer date, commercial production in the area of today s Republic of Srpska started in At the beginning, it spread in Croatia, in Virovitica area in social sector, in the former Yugoslavia, which was the base for its spreading in cooperation over individual producers. There was significant effort made for introduction of Virginia to other production areas of the former Yugoslavia, as well as to the area of today s Republic of Srpska. Requested quality of Virginia tobacco could be achieved through model production. Conditions for successful production of Virginia, in the first place, are proper choice of land of satisfying physical-chemical features and climate in the aspect of sum of temperatures and rainfalls in the growing period, as well as choice of proper varieties and drying performed in quality way. Due to this, we believe that research of physical characteristics, apart from other features of the American tobaccos produced in the area of Republic of Srpska, has contributed both evaluating results from the production of this tobacco so far, and reviewing of the further possibilities of intensifying production of this type of tobacco, which is used in production of cigarettes the main goal of this research. In Republic of Srpska area, Virginia tobacco has been grown successfully due to similarity of climate and pedological conditions of production with conditions of growing in the USA, where this tobacco originates from. Materials and methods Nowadays, Virginia tobacco is being grown in the fields of 800 hectares in production area of Republic of Srpska, namely on dominant types of land and various environments. 70

3 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Material used for research comes from Virginia variety DH 17, from the area of Bijeljina, and Hewessi 17, from the area of Donji Žabar. There have been three-year researches in the period from 2004 to The middle leaves are of the best quality in Virginia tobacco. Quality drops as going from middle part forward lower and upper position of the leaves on the stalk. In order to review physical characteristics of researched material in a more complex manner, the samples of middle leaf were selected in three variants: lower middle, actual middle and upper middle leaf for both varieties for all three tested years. These three variants of middle leaf were selected for research since provided insertions take 70% part in mixing formula for cigarettes. Leaves of fermented tobaccos, processed in standard procedure, were used for research. During the research, there were six samples per a year, which is 18 in total for three years. Each chosen tobacco sample was used for determining physical parameters: length, width, thickness of tobacco leaf, main nerve content in total mass of the leaf tissue and substantiality of the leaf tissue. Physical characteristics of the tobacco were determined in accordance with internationally recognized methods, which are accepted and applied in the Tobacco Institute Prilep, Republic of Macedonia. Results are presented in tables and in graphs. Significance of results and difference in the reference to quality characteristics of tobacco were established through statistic analysis of variant using LSD test. Climatic Conditions Three-year data for air temperature and rainfalls as basic climatic elements for formation of physical characteristics of tobacco presented in Tables 1.,2.,3. and 4. During growing period of tobacco, average air temperature in the area of Donji Žabar (Table 1) was C and is higher than multi-year average, which is C. However, in May, when tobacco is replanted, the air temperature is C, and in period when tobacco grows intensively (June and July), average air temperature is higher, which is an evidence that tobacco plant has enough warmth for undisturbed growth on field. Likewise, during growing period of tobacco, average air temperature in the area of Bijeljina (Table 2) was C and is lower than multi-year average, which is C. However, in May, when tobacco is being replanted, air temperature is C, and in the months when tobacco grows intensively (June and July), average air temperature is higher, which is an evidence that tobacco plant has enough warmth for undisturbed growth and development on field. 71

4 72 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Table 1. Average monthly air temperatures ( C) during growing period (from V to IX) in the area of Donji Žabar Average Month May June July August September Average Month Table 2. Average monthly air temperatures ( C) during growing period (from V to IX) in the area of Bijeljina Average May June July August September Average Data in Table 3, expressing rainfall in the area of Donji Žabar during research, show that year 2004 was the driest year with 426 mm of precipitation in growing period. The highest amount of rainfall was in mm, and in mm. These amounts of rainfalls satisfy tobacco needs for water in growing period. However, amounts of rainfalls have not been distributed equally, so it is necessary to irrigate additionally. 72

5 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Month Table 3. Rainfall sum (mm) during growing period (from V to IX) in the area of Donji Žabar Average May June July August September Sum for growing period Annual sum In accordance with Table 4, expressing rainfall in the area of Bijeljina during research, it is evident that year 2006 was the driest year with mm of precipitation in growing period. The highest amount of rainfall was in mm, and in mm. These amounts of rainfalls satisfy tobacco needs for water in growing period. However, amounts of rainfalls, just like in case of Donji Žabar area, have not been distributed equally, so it is necessary to irrigate additionally. Table 11. Rainfall sum (mm) during growing period (from V to IX) in the area of Bijeljina Month Average May June July August September Sum for growing period Annual sum

6 74 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Results and Discussion Physical characteristics of raw material It could be claimed that physical characteristics of tobacco leaf, more than any other of its characteristics, reflect conditions in which tobacco was grown. Apart from variety, physical characteristics depend on lots of factors, such as: climatic conditions, application of agricultural engineering, way of drying and procession, position of the leaf on the stalk, as well as leaf ripening in the moment of tobacco harvest. Tobacco leaf length(cm) Tobacco leaf length is one of the most important characteristics of a variety. It changes for the leaves taken from different insertions, although leaves of the middle insertion always are the longest. Maksimović (1986) says that tobacco leaf length depends on growing location, way of nutrition, irrigation and other agricultural engineering measures. Results of studying tobacco leaf length in testing material are shown in Table 5. Table 5. Virginia tobacco leaf length (cm) Varieties DH - 17 Insertions Lower Middle Upper Hewessi Basic factor C, X average Data of average values direct to certain laws, which show that the longest was the leaf of middle insertion (48.68cm), then leaf of upper of 74

7 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) insertion comes (36.48cm), and the smallest length was in the leaf of lower insertion (35.76cm). Analysis of variant of average leaf length with tested Virginia tobacco varieties shows statistically significant interaction effect between year and insertion provided in Graph 1. Graph 1. Interaction effect year and insertion InteractionBC Lower Middle Upper s Demonstrated deviation, implied by interaction effect, is referred to tobacco leaf length of lower insertion in Average leaf length of lower insertion was bigger in comparison to upper insertion, which is a consequence of agricultural-climatic conditions, although, in accordance with spotted tendencies, it was expected to have a lower value. On the basis of variant analysis, it could clearly be concluded that length of variety Hewessi 17 is significantly bigger in comparison to DH 17. Tobacco leaf width (cm) As a rule, tobacco leaf width is about 50% less in comparing to its length. Relation between length and width is expressed in tobacco practice. This relation could serve better to selectors in further research of new and improvement of existing varieties than it is significant in tobacco practice itself. A request for production of tobaccos with longer and narrower leaves appear in tobacco technology. This is important from the aspect of better use of sun light, mechanized harvest is facilitated, as well as drying of tobacco (Maksimović, 1986). 75

8 76 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Results of three-year research of tobacco leaf width are provided in Table 6. Table 6. Virginia tobacco leaf width (cm) Varieties DH - 17 Insertions Lower Middle Upper Hewessi Basic factor C, X average Analysis of variant of average leaf width with tested Virginia tobacco varieties does not show statistically significant interaction effect, so that conclusions could be in accordance with average values of basic factors. In analysis of results provided in Table 6, it could be seen that the largest width of tobacco leaf has the leaf of middle insertion (22.66cm), then the leaf of lower insertion comes (19.54cm), and the leaf of upper of insertion has the smallest width (16.49cm). Tobacco leaf thickness (µ) Tobacco leaf thickness is a physical characteristics used for evaluation of tobacco quality. Leaf thickness is a component used for determination of tobacco leaf tissue fullness. Tobacco leaf thickness is in a positive correlation with tobacco leaf tissue fullness. Thin tissue usually is fuller, i.e. has more contents. It means that this type of tissue is featured with increased "sponge" spaces, which is featured with deficit in positive organic substances. Smaller thickness shows higher quality of tobacco, so thin leaves are result of starving tobacco leaves. Tobacco leaf thickness depends on variety, soil-climatic conditions and application of agricultural engineering measures in growing period. 76

9 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Filiposki (1986) says that mineral nutrition and increased land humidity affect decrease of leaf thickness. Tobacco leaf thickness varies per insertions, years and along the leaf itself. If one analysis a leaf, it could be noted that it is not of same thickness. Width of leaf blade increases from the base toward top, and it is vice versa at the main nerve: in is the thickest at the base and the thinnest at the top. Results from threeyear research are presented in Table 7. Table 7. Virginia tobacco leaf thickness (µ) Varieties DH - 17 Insertions Lower Middle Upper Hewessi Basic factor C, X average Analysis of variant of average leaf width with tested Virginia tobacco varieties does not show statistically significant interaction effects, so that conclusions could be in accordance with average values of basic factors. The thickest is the leaf of upper of insertion (141.96µ), then the leaf of middle insertion comes (125.17µ), and the smallest thickness is with the leaf of lower insertion (121.69µ), which directs to certain laws. Average tobacco leaf thickness of the tested varieties shows that variety Hewessi 17 has thicker leaf in average (134.72µ) in comparison to variety DH 17 (124.48µ). Tobacco leaf thickness shows that the leaf was the thickest in 2004 out of tested years, and thickness was the smallest in 2006 in both varieties, which implies that agricultural-climatic conditions influenced this physical characteristic in growing period. 77

10 78 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Substantiality of leaf tissue (g/m 2 ) Substantiality of the leaf tissue is also known as fullness of leaf tissue. This characteristic depends more on leaves structure and less on chemical structure. Substantiality of the leaf tissue is contents of dry substance in a unit of leaf surface expressed in g/m 2. Substantiality of the leaf tissue can be positive and negative index of tobacco quality. In the reference to substantiality of quality tobaccos, those with dominating material components (aromatic substances and soluble sugar) those having positive influence on quality and are marked as concentrated tobaccos. Fullness of the tissue is considered to be very important tobacco characteristic, since it produces bigger or smaller amount of fullness, as well as more profitable usage in making cigarettes. Full and empty tobaccos, which have very high or very low substantiality, are negative indexes for tobacco quality. Application of agricultural engineering measures, fertilizing and irrigation, have certain influence on substantiality of tobacco leaf. Filiposki (1986) has stated that mineral nutrition and exceeding humidity have significant influence on decrease of substantiality of tobacco type Prilep. Lazaroski (1983) has stated that substantiality of the leaf tissue shows significant dependency of providing plants with water during growing period. Uzunovski (1985) has stated that tobaccos being produce fertile land, which have been fertile with azotic fertilizer, usually, are full tobaccos. Study of substantiality of the leaf tissue with tested varieties of Virginia tobacco, are provided in Table 8. Table 8. Virginia tobacco leaf substantiality (g/m 2 ) Varieties DH - 17 Insertions Lower Middle Upper Hewessi Basic factor C, X average

11 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) In analysis of data provided in Table 8, it could be concluded the leaf of middle of insertion has the least average substantiality of the leaf tissue (62.21 g/m 2 ), then the leaf of lower insertion comes (62.89 g/m 2 ), and the leaf of upper of insertion has the largest substantiality (78.33 g/m 2 ). Analysis of variant shows significant interaction effect between variety and year, which is provided Graph 2. Graph 2. Interaction relation between variety and year Interaction AB DH - 17 Hewessi Graphic analysis shows that average substantiality of the leaf tissue with variety DH 17 is larger than with variety Hewessi 17. Substantiality of the leaf tissue with both tested varieties is larger in 2005 in comparison to 2006, while in 2004, it demonstrated deviations from the expected, which is implied by interaction effect. Deviation was caused by agricultural-climatic conditions. Results of the study in substantiality of the leaf tissue are close to results of those represented in available literature. Substantiality of the leaf tissue is a positive index of quality, which would be confirmed in cigarette production, since 1 kg of cut tobacco produces bigger number of cigarettes. Study of number of cigarettes, made out of 1 kg of cut tobacco with tested varieties, is provided in Table 9. In analysis of Table 9, it could be stated that the smallest number of cigarettes has been made of the leaf of lower insertion (1009), then the leaf of upper insertion comes (1075), and the biggest number of cigarettes has been made out of the leaf of middle insertion (1121). 79

12 80 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Table 9. Number of cigarettes made out of 1 kg of Virginia tobacco Varieties DH - 17 Insertions Lower Middle Upper Hewessi Basic factor C, X average Analysis of variant of average number of cigarettes made out of 1 kg of cut tobacco statistically significant interaction effect between year and insertion provided in Graph 3. Graph 3. Interaction effect between variety and year Interaction AB DH - 17 Hewessi Graphic analysis of interaction effect provides conclusion that average number of cigarettes made out of 1 kg of cut tobacco is bigger with variety DH 17 in comparison to variety Hewessi 17. Demonstrated deviation implied by interaction effect refers to number of cigarettes made out of 1 kg of cut tobacco in 2005 with variety DH 17, when it was statistically significantly bigger in comparison to variety Hewessi 17 in the same year. 80

13 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Main nerve content in total mass of a leaf (%) Structure of a leaf comes from its function and contents of chemical components. Tobacco leaf consists of two parts: nerve and leaf blade. Nerve is located at the middle of the leaf, across its length, from base to the top. Nerve is different from the leaf blade in both chemical constitution and technological characteristics. Leaf blade, in difference to the nerve bears biochemical and physical characteristics of a leaf. Contents of the nerve, in comparison to total leaf mass, points out to leaf fineness and leaf thickness, which has a negative effect in cigarette production, due to increased specific weight, as well as due to negative effect to the composition (length) of tobacco tissue. Modern processing of tobacco, with introduction of re-drying systems with threshing, has provided extraction of the main nerve and its physical transformation (expanding) for easier usage in cigarette mixture. Use of expanded main nerve in cigarette mixture, first of all, affects increase of power of filling material. So, content in the amount of 25% of the main nerve in composition of the tobacco leaf is not a problem any longer, as it used to be. Nowadays, we use expanded nerve in the amount of 10% - 20 % in tobacco mixture. In some world tobacco companies, expanded nerve s content in tobacco mixture is up to 30 %. Expanded nerve has a significant influence on reduction of tar and nicotine in tobacco smoke, too. Use of expanded nerve is especially increased in tobacco mixture with passing the Law of the World Health Organization for reduction of tar and nicotine in tobacco smoke of a cigarette. However, it is obvious that content of expanded nerve takes place significantly in technology of tobacco mixture, not only in reduction of tar in tobacco smoke but also in price of the mixture for production of cigarettes. Filiposki (1986) has stated that irrigation and fertilizing affect on increase of content of the main nerve in overall mass of the tobacco leaf. Iskilieva (1969) has stated that content of the main nerve with tobacco with big leaves amounts from 28.70% to %. Ishity (in accordance to statements of Maksimović, 1986) points out to the fact that topping and removal of cotters affects increase of leaf blade weight towards nerve especially in upper harvesting. Anyway, increase of the main nerve should be seen from the point of leaf size and, due to this, it is a relative size. Maksimović (1986) has stated that content of the main nerve in Virginia tobaccos in the area of Veliko Gradište amounts from 23.27% to %. Results of studying content of the main nerve in overall mass of the tobacco leaf are within the frame of studied material given in the bibliography. Study of the content of the main nerve in overall mass of the tobacco leaf of Virginia tobacco is provided in Table

14 82 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) Table 10. Content of the main nerve in overall mass of the tobacco leaf (%) Varieties Insertions Lower Middle Upper DH Hewessi Basic factor C, X average Since analysis of variant of studying content of the main nerve in overall mass of the tobacco leaf does not show statistically significant interaction effects, so that conclusions could be in accordance with average values of basic factors. The biggest content of the main nerve is in the leaf of middle insertion (25.00%), then the leaf of lower insertion comes (20.99%), and the smallest is with the leaf of upper insertion (18.12%). Average content of the main nerve in overall mass of the tobacco leaf shows that variety Hewessi 17 has bigger content of the main nerve in average (23.47%) in comparison to variety DH 17 (19.27%). The biggest content of the main nerve in overall mass of the tobacco leaf was in 2004 (23.85%), and smallest in 2005 (18.97%). In testing significance through LSD test, it has been concluded that content of the main nerve in overall mass of the tobacco leaf in 2004 in variety Hewessi 17 has had significantly bigger values and agricultural-climatic factors affected as well. Conclusion On the basis of produced results, it could be concluded that: Judging by multi-year data, meteorological factors in the area of Republic of Srpska are in accordance with tobacco type. Temperature conditions were of such values that they were favorable for successful production of Virginia tobaccos. Average rainfall could be considered to be satisfactory. However, rainfalls in growing period are not equally distributed. These data surely point out to 82

15 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) necessity of application of proper agricultural engineering measures in the aim of achieving proper quality of raw material. Tobacco leaf length in studied samples amounts from cm to cm. The longest was the leaf of middle insertion, in both studied varieties and in all three years, then leaf of upper of insertion comes, and the smallest length was in the leaf of lower insertion. On the basis of variant analysis, it could clearly be concluded that length of variety Hewessi 17 is significantly bigger in comparison to DH 17. Tobacco leaf width in studied samples amounts from cm to cm. The largest width of tobacco leaf has the leaf of middle insertion (22.66cm), then the leaf of lower insertion comes (19.54cm), and the leaf of upper of insertion has the smallest width (16.49cm). Variety Hewessi 17 has wider leaf (20.20 cm) in comparison to variety DH 17 (18.93cm). Tobacco leaf thickness of the studied varieties amounts from µ to µ. Virginia tobacco of variety Hewessi 17 (134.72µ) has thicker leaf in average in comparison to variety DH 17 (124.48µ). The tobacco leaf is the thickest in 2004 ( µ), and the thinnest is in 2006 (86.32 µ). The thickest is the leaf of upper of insertion (141.96µ), then the leaf of middle insertion comes (125.17µ), and the smallest thickness is with the leaf of lower insertion (121.69µ). Substantiality of the leaf tissue in studied samples amounts from to g/m 2. The largest substantiality of the leaf tissue has the leaf of upper of insertion, then lower insertion comes, and the least substantiality of the leaf tissue has the leaf of middle of insertion. Average substantiality of the leaf tissue with variety DH 17 is larger than with variety Hewessi 17. Substantiality of the leaf tissue with all the varieties is a positive index of quality, which is confirmed by number of cigarettes produced out of 1 kg of tobacco. Number of cigarettes produced out of 1 kg of tobacco of the studied samples amounts from to The biggest average number of cigarettes has been made out of the leaf of middle insertion ( ), then the leaf of upper insertion comes ( ), and the smallest average number of cigarettes has been made of the leaf of lower insertion ( ). In average, biggest number of cigarettes is produced from variety DH 17 in comparison to variety Hewessi 17. Contents of the main nerve in overall mass of the tobacco leaf with studied samples amounts from 14.57% to %. Variety Hewessi 17 has bigger content of the main nerve in average (23.47%) in comparison to variety DH 17 (19.27%). The biggest content of the main nerve is in the leaf of middle insertion (24.99%), then the leaf of lower insertion comes (20.99%), and the smallest is with the leaf of upper insertion (18.12%). 83

16 84 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) References A b d a l l a h F. (1968).: Can tobacco quality be measured. Tobacco USA, 166 (8). Akehurst B.C. (1968).: Tobacco. Humanites press, New York. A l ić D ž e mi d ž ić N. (1972).: Savremeni tehnološki proces prerade duvana. Tutun, 3-4, Prilep. A l ić D ž e mi d ž ić N. (1975).: Značaj i uloga hemijskih komponenata i fizičkih osobina sirovina u sastavljanju standardnih mješavina pri izradi cigareta. Beograd. G a r n e r W. W. (1951).: The production of tabacco. New York. H a w k s J r. (1970).: Principles of flue cured tobacco production. Raleigh. H a w k s S. N., C o l l i n s W. K. (1994).: Načela proizvodnje virginijskog duhana (prevod). Zagreb. F i l i p o s k i K. (1986).: Uticaj mineralne ishrane na potrošnju vode i kvalitet duvana tipa Prilep. Doktorska disertacija. Beograd. M a k s i mo v ić S. (1986).: Uticaj đubrenja na prinos i kvalitet virdžinijskih duvana. Doktorska disertacija. Beograd. L a z a r o s k i T. (1983).: Uticaj navodnjavanja na prinos i tehnološka svojstva orijentalnog aromatičnog duhana sorte prilep. Doktorska disertacija. Beograd. U z u n o v s k i M. (1985).: Proizvodstvo na tutun. Skopje. Is k i l i e v a V. (1969).: Hemisko - tehnologičesko proučuvawe na tutuna barleı, proizveden u nas. Blgarski tutun, broı 2, godina XIV str

17 NEKE FIZIČKE KARAKTERISTIKE DUVANSKE SIROVINE TIPA VIRDŽINIJA SA PROIZVODNOG PODRUČJA REPUBLIKE SRPSKE - originalni naučni rad - Obrenija Kalamanda Fabrika duvana, Banja Luka, Republika Srpska Valentina Pelivanoska Institut za tutun, Prilep, Republika Makedonija Rezime Fizička svojstva duvanskog lista su odraz uslova u kojima je duvan gajen. Osim od sorte, fizička svojstva zavise od klimatskih uslova, primenjene agrotehnike, načina sušenja i obrade, položaja lista na stabljici, kao i zrelosti lista u momentu berbe duvana. U radu su izneti rezultati ispitivanja fizičkih karakteristika virdžinijskih duvana (sorte DH - 17 sa područja Bijeljine i sorte Hewessi 17 sa područja Donji Žabar) pored ostalih svojstava, kako bi se procenila upotrebna vrednost ovog tipa duvana koji se koristi u fabrikaciji cigareta. Da bi se što kompleksnije sagledale fizičke karakteristike ispitivanih materijala odabrani su uzorci srednjeg lista u tri varijante: donji srednji, pravi srednji i gornji srednji. Ove tri varijante su odabrane za istraživanja zato što u 70% slučajeva date insercije učestvuju u mešavinama cigareta. Od fizičkih svojstava određivani su: dužina, širina, debljina duvanskog lista, materijalnost lisnog tkiva i sadržaj glavnog rebra u ukupnoj masi lista. Dužina lista je jedna od najvažnijih sortnih karakteristika. Rezultati ispitivanja su različiti i zavise od položaja lista na struku. Najveća dužina je na pravom srednjem listu kod obe sorte, kod sorte DH 17 kreće se od 42,90 49,20 cm, a kod Hewessi 17 od 49,30 52,36 cm. Najmanju širinu ima gornji srednji list 16,49 cm, a najveću širinu ima pravi srednji list 22,66 cm. Najveću debljinu ima gornji srednji list 141,96 µ, a najmanju donji srednji list 121,69 µ. Sorta Hewessi 17 ima deblji list u odnosu na sortu DH 17. Za materijalnost lisnog tkiva najveću vrednost ima gornji srednji list 78,33 g/m 2, a najmanju pravi srednji list 62,21 g/m 2. Veću materijalnost lisnog tkiva pokazuje sorta DH 17. Sadržaj glavnog rebra predstavlja važan fizički parametar kvaliteta duvana. Zastupljenost glavnog rebra

18 86 Acta Agriculturae Serbica, Vol. XVIII, 35 (2013) u ukupnoj težini lista je najveća u pravom srednjem listu 25%, a najmanja u gornjem srednjem listu 18,12%. Sorta Hewessi 17 pokazuje veću zastupljenost glavnog rebra. Istraživanja pokazuju da na fizičke karakteristike virdžinijskih duvana proizvedenih na području Republike Srpske uticaj imaju klimatski uslovi u toku vegetacije, a dobijeni rezultati su slični rezultatima koji su prezentovani u dostupnoj literaturi. Ključne reči: duvan, Virdžinija. 86