Field experiment was conducted to get the basic information about the difference in color and plastid pigments at the different stage of harvest of flue-cured tobacco cultivated in paddy field, and compared to upland ones. All tested crops were primed in lots of 3 to 4 at each priming, beginning at the bottom of the plant. Leaf pigments and chromatic values of tobacco leaves were determined in samples collected at weekly intervals, and according to analyses obtained from 4 stalk positions. By the degree of maturity, leaves harvested were separated with visual characters into four classes of immature, mature, ripe and mellow. regardless of stalk position, chlorophyll contents was higher in the order of immature > mature > ripe > mellow, respectively. In fresh leaves, chlorophyll levels was higher with ascending stalk position. chlorophyll a and b in cured leaves were less than 10% of the amount present at harvest, and it was estimated that maturity condition also influenced the rates of degradation of plastid pigments. Fully mature leaves of upland diverted from paddy field showed slightly higher in chlorophyll contents than in those of upland tobacco ones but somewhat lowered in $L^*$ and $b^*$ values, and there was no difference in $a^*$ value.

The spermatogenesis and chromosome number were investigated in the pupal testes of Helicouerpa assulta Guenee by light microscopy. During the spermatogenesis, each bundle of P8(256) sperms developed by 6 mitotic and 2 meiotic spermatogonial divisions. From the early stage of spermatogenesis, it was distinguishable between two kinds of sperm differentiation, eupyrene and apyrene spermatogenesis, which are characteristic in Lepidoptera, by the differences in nuclear shape and cell distribution in immature spermatocyst. Through the followed spermiogenesis, the spermatocysts were developed into two kinds of mature cyst, a streamline-shaped eupyrene cyst with nucleated sperms of thready head or a long spindle-shaped apyrene cyst with anucleated sperms of cylindrical head. As the results off chromosomal analysis at metaphase of the spermatogonial mitosis and spermatocytic meiosis, the chromosome number were 2n=6a/n=31, respectively, and no variation between individuals.

Tobacco plants resistant (cvs. Xanthi-nc and Samsun-NN) and susceptible (cv. NC 82) to tobacco mosaic virus (TMV) were inoculated with TW to obtain basic information about the characteristics of resistance expression in tobacco plants by examining the viral populations, symptom development and gene expression of pathogenesis-related proteins (PR-proteins) such as PR-1 and $\beta$-1, 3-glucanase in different temperature conditions. TMV populations in resistant plants increased more at 37$^{\circ}C$ than at 27$^{\circ}C$, while the viral populations increased continuously and were not significantly influenced by the temperature conditions in the susceptible tobacco plants. Infection sites of resistant tobacco leaves were remarkably expanded in proportion with increased time at the high temperature.

Meiotic metaphase chromosomes of the testis of two storage insects, tobacco moth (Ephestia elutella H.) and cigarette beetle (Lasioderma serricorne F.) were examined to study their karyotypes. The number of haploid chromosomes of the tobacco moth was 31 and the karyotype was characterized by 29 metacentric and 2 submetacentric chromosomes. The metaphase chromosome length of tobacco moth ranged ca. 1.44-2.11${\mu}{\textrm}{m}$ and the average length was 1, 78${\mu}{\textrm}{m}$. The number of haploid chromosomes of the cigarette beetle at metaphase was 10 and the karyotype was characterized by 8 metacentric and 2 submetacentric chromosomes. The range of metaphase chromosome length of the cigarette beetle was ca. 1.79- 2.39${\mu}{\textrm}{m}$ and the average length 2.09${\mu}{\textrm}{m}$.

A storage protein(SP-2) was confirmed in haemolymph during larval-pupal-adult development of tobacco burdworm(Helicoverpa assulta Guenee), and its biochemical characteristics were investigated. The titer of SP-2 showed a peak at mature larva, decreased gradually through the late pupal stage, and became undetectable at adult period. As the results from electrophoretic mnysis, SP-2 was confirmed to be glycolipoprotein(M.W. 332kDa) relatively stable to heat( $\leq$ 68$^{\circ}C$ ). This storage protein was determined to be a tetramer composed of a single subunit with MW of 83kDa, and the isoelectric point was 5.7. The amino acid composition of the SP-2 was characterized. It has relatively high content of methionine and histidine, whereas the contents of tyrosine and phenylalanine were relatively low.

This experiment was carried out to study the effect of oxygen on chemical composition and physical properties of tobacco leaves during flue-curing. The results obtained were as follows: Starch content decreased and sucrose content increased with increasing oxygen supply during curing. Glucose and fructose of the cured leaves showed high content at the 5-10% oxygen supply. Amino-N and nitrate-N increased with increasing oxygen supply. Total nitrogen and NH4-N showed the lowest value at the 5-10% and 10-15% oxygen supply in the cutters and leaf, respectively. Chlorophyll and chlorogenic acid increased, and total volatile base decreased with increasing oxygen supply. The activity of α-amylase increased at the latter period of flue-curing, and the maximum activity point were delayed 12 hours with increasing oxygen supply. Shatter index of cured leaves decreased with increasing oxygen supply. It was desirable to supply oxygen during flue-curing for the improvement of chemical and physical properties such as starch, total sugar, chlorogenic acid, and shatter index of cured leaves.

Erwinia carotovora subsp. Carotovora (Ecc), a pathogen of tobacco hollow stalk disease, was isolated for testing susceptibility to streptomycin from diseased plants in burley tobacco growing area. Of 157 isolates tested, 17 isolates (108%) were resistant to the antibiotic at the antibiotic from field soils, which streptomycin had been used continuously for three years for control of the disease was three times higher than those of non-used. There was no difference in virulence and generation time between streptomycin-sensitive and resistant strains.

Chemicals including antibiotics and bactericides were screened for suppression of streptomycin-resistant Erwinia cmutouom subsp. cmutovom (Ecc) strains in laboratory and field conditions. Oxytetracycline, ethoquinolac and dichlorophen suppressed the growth of streptomycin-resistant Ecc strains in vitro. Fractional inhibitory concentration (FIC) indices of oxytetracycline and ethoquinolac mixed with streptomycin against the Ecc strains were equal to and less than one, respectively. Consequently the efficacy of those chemicals in mixture with sorptomycin were non-antagonistic But that of dichlorophen mixed with streptomycin was more than one, therefore the efficacy of the mixture was antagonistic. Spray of oxyteoucycline, ethoquinolac and agrimycin-100 on the topped burley tobacco plants was efficacious in reducing tobacco hollow stalk at the same level of sorptomycin treatment in three-year field trials, which suggests that those are promising chemicals to be alternative to streptomycin for control of tobacco hollow stalk.

This study was carried out to investigate the effects of high temperature and humidity on the ageing of processed leaf tobacco. Four(1993) or six(1994) grades (Both flued-cured and burley) of processed leaf packed in carton box were stored under the natural and artificial conditions. When the Processed leaf was stored in the controlled mom at 40℃ with 75% R.H.(1993) for 40 days, the leaf pH was decreased. The decreasing rate of leaf pH was similar to that of leaf stored under the natural warehouse condition for 15 months. The degree of lightness and yellowness of leaf also decreased, while the decaying or darkening of the leaf was observed. When the processed leaf was stored in the controlled room at 35℃ with 65% R.H.(1994) for 90 days, the pH of flue-cured was decreased 0.22, which was similar to that of the leaf stored under the natural warehouse condition for 15 months, and the lightness, and redness of the leaf were higher than those of the control. As compared with the leaf stored under the natural condition for 2 years, the smoking quality of leaf stored under this condition was similar or somewhat better. The pH of burley tobacco changed little compared to that of flue-cured during storage in this study.

Flue-cured tobaccos(cv. NC82, grade AB3O-1) expanded by super steam, volatile organic solvents(tricuorofluoromethane, propane), carbon dioxide, nitrogen, and by freeze-drying were examined for their physico-chemical properties. The expanding rate by using the organic solvents or carbon dioxide at the impregnated pressure was 70% or more, whereas the rate by super steam and freeze-drying was 49.4 and 42.9%, respectively. The contents of total sugar, alkaloid and ether extracts of the expanded tobacco by organic solvents or carbondioxide were decreased to 27.6, 20% or more, and 13%, respectively, when compared to non-expanded one. The contents of citric acid of the tobacco expanded by using trichlorofluoromethane and carbon dioxide were increased to 19.1, 14.0%, respectively. Linoleic acid in the tobacco expanded by super steam or trichlorofluoromethane was also increased to 17.3%, but malonic acid in the tobacco expanded by super steam was 18.5% less than that in the non-expanded one. Nineteen essential oil among 22 assayed in this experiment were decreased in the expanded tobaccos. Key words : expanding method, tobacco, physico-chemical properties.

Commercially available activated carbon was treated with 0.2N NaOH/0.1N HCl to decrease the ash contents and to analyze the effect of demineralization. We have studied their properties and adsorptivity to solvents such as benzene, acetone, toluene and carbon tetrachloride, ammonia and also aldehydes of cigarette smoke. By demineralization with NaOH/HCl, surface area and pore volume were increased up to 10 - 20% according to developement of micro-pore and pH of activated carbon was also changed from 10.2 to 6.3. Surface acidity of the activated carbon treated with chemicals increased slightly. The chemical treatment led to small increase in adsorptioil properties of solvents, ammonia and aldehydes of cigarette smoke, but content of chlorine and sulfur in activated carbon were reduced. As the results of smoking test, charcoal taste caused by the activated carbon was reduced significantly by the treatment with NaOH/HCl.

A mathematical model of the pressure gradient of supercritical CO2 in a vertical tobacco bed was developed in this study. In particular, the compaction of the tobacco as a function of temperature and CO2 flow is included in the model. Downflow of CO2 (low condition is described. At velocities in excess of 0.6 cm/sec at 7$0^{\circ}C$, there is a large increase in pressure gradient for beds deeper than about 0.5 m. The proposed model offers a better understanding of operating the process using supercritical CO2.