Studies On The Characteristic Of Sulfur And Regulatory Measures Of Flue-cured Tobacco

Field sampling experiment was carried out to analyze and estimate soil available sulfur and tobacco leaf sulfur contents of tobacco-planting area in Hunan and the correlation between sulfur contents and internal quality of tobacco leaves.Solution culture experiment and fertilizing experiment were carried out to study dry matter accumulation and N, P,K,Ca,Mg,S,B,Mn,Zn,Cu nutrient element uptake rule,and the effects of different sulfur concentration on photosynthesis,chlorophyll fluorescence parameters and other physiological and chemical index.Simulated acid rain experiment was carried out to study the effects of different pH value on chlorophyll contents,photosynthesis,chlorophyll fluorescence parameters and sulfur content in flue-cured tobacco leaf.Different cropping patterns and genotype comparison experiment were carried out to find out suitable cropping patterns and tobacco varieties.The results are as follows:1.The contents of available sulfur in tobacco planting soil and sulfur in tobacco leaves are on the high side in Hunan.The average contents of available sulfur in tobacco planting soil were 34.74 mg/kg,about 80%of total tobacco planting areas was on the high side.The average tobacco leaf sulfur contents were 0.849%,about 70%tobacco leaves sulfur content were over 0.70%,especially in Liuyang and Ningxiang county where tobacco leaf sulfur contents were above 1.00%.The contents of available sulfur in soil and sulfur in tobacco leaf from tobacco-rice continuous cropping pattern were remarkable higher than that from single cropping pattern in dry land.The average contents of available sulfur in soil and sulfur in tobacco leaf from tobacco-rice continuous cropping pattern were 39.06 mg/kg and 0.968%,and 30.42 mg/kg and 0.704%for single cropping in dry land respectively.The available sulfur and total sulfur contents were remarkable increased from 1 to 15 years and were steady after 15 years in continuous tobacco planting soil.There was significant negative correlation between tobacco leaf sulfur contents and total sugar and moisture contents.Sulfur contents were extremely significant negative correlation with aroma quality,lingering odor,total smoking quality scores and Potassium(K) contents of tobacco leaf,no significant positive correlation with total nitrogen, total chlorine,and total alkaloid in tobacco leaf,no significant negative correlation with aroma quantity,offensive odor,physical strength,aroma odor,combustibility,ash color,total particle shape contents,nicotine quantity in smoking gas,and tar quantity.2.Well-balanced S supply could promote tobacco growth and development,dry matter accumulation,nutrient uptake,yield and production value.Excessive sulfur supply could significantly decrease plant height,stem girth,maximum leaf area,node interval,root volume, and so on.Sufficient sulfur supply could significantly promote tobacco S nutrient uptake. Optimal S supply is 2 mmol/L in solution culture experiment and 50 kg/hm² in fertilizer experiment.0 mmol/L and 2 mmol/L treatments significantly promoted tobacco dry matter accumulation and N,K,Ca,B,Mn,Zn,Cu nutrient element uptake.2～4 mmol/L treatments promoted P and Mg nutrient uptake.Further increase sulfur concentration resulted in a decrease in these nutrient elements uptake and dry matter accumulation.3.Chlorophyll contents,net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),intercellular CO₂ concentration(Ci),vapor pressure deficit(VPD),water use efficiency(WUE) and intrinsic water use efficiency(WUEi) were promoted but stomatic limited value(Ls) was decreased when sulfur supply was 2～4 mmol/l and 50～100 kg/hm².The effective PSII quantum yield(EQY),the electron transport rate(ETR) and the coefficient of photochemical quenching(qP) were increased and the coefficient of non-photochemical quenching(NPQ) was reduced simultaneously when S concentration was 2～8 mmol/L.The root activity of tobacco was stronger in the treatments of 0 mmol/L and 2 mmol/L and that were reduced with sulfur concentration increase in the treatments of 4 to 32 mmol/L.The NR activity of 2 mmol/L and 4 mmol/L treatments was higher than that of other treatments.The activity of SOD and POD of tobacco leaves was significantly increased with sulfur concentration increasing. MDA content of tobacco leaves was lowest in 2 mmol/L treatment and increased gradually with sulfur concentration increase in other treatments from rosette stage to budding stage.But MDA content of tobacco leaves was not significantly different in maturation stage.The Proline contents under 16 mmol/L and 32 mmol/L were significantly higher than under other treatments at rosette stage while the Proline contents under the 8 mmol/L and 16 mmol/L were highest from fast growing to maturation stage.4.The leaf thickness was reduced significantly when sulfur concentration was 16 mmol/L. The leaf epidermis thickness was significantly higher at 0 mmol/L while its width was lower than that of other treatments.The leaf lower epidermis thickness was significantly increased at 2 mmol/L treatments and its width was yet significantly increased at 0～4 mmol/L treatments. Sulfur supply at 0～4 mmol/L increased significantly palisade tissue thickness.The palisade tissue interspace at 0 mmol/L and 4～32 mmol/L treatments was significantly higher than that of 2 mmol/L treatment.The thickness and interspace of spongy tissue and thickness ratio of spongy tissue to leaf were decreased at 0 mmol/L and 8～32 mmol/L treatments significantly.The thickness ratio palisade tissue to leaf and spongy tissue were increased at 0 mmol/L treatment significantly.5.Simulated acid rain with pH≥3.5 had no significant influence on chlorophyll contents and Pn of tobacco leaves while chlorophyll content,Pn,Ci,VPD,WUE and WUEi of the treatments with pH≤2.5 were significantly lower than that of control.Ls of pH 2.0 treatment was significantly higher than that of control,pH≥3.5 treatments had no significant difference with control at EQY,ETR,and qP while that of the treatments with pH≤3.0 were reduced.All treatments were higher than control at NPQ,but that of pH≥3.5 treatments were higher than that of pH≤3.0 treatments.The activity of SOD and POD and the contents of Proline and soluble protein were significantly increased with pH value reduced while the activity of SOD and the contents of Proline were significantly reduced at pH≤3.0.Simulated acid rain reduced significantly the activity of NR and the contents of soluble sugar.The contents of total sugar,reductive sugar and the ratio of total sugar to total N were not significantly different with control at pH≥3.5 treatments while that of pH≤3.0 treatments were significantly lower than that of control.The sulfur contents of leaf were increased along with pH value reduced.The yield and production value of pH≤4.0 treatments were significantly reduced although the sulfur content of total treatments had no significantly difference with control.The thickness of leaf was significantly reduced along with pH value reduced.The palisade tissue thickness of pH≥3.5 treatments was significantly higher than that of pH≤2.5 treatments. The thickness of spongy tissue of pH≤3.0 treatments was significantly lower than that of control and other treatments.The thickness ratio of palisade tissue to leaf of pH≥3.0 treatments was significantly higher than control while that of other treatments had no significant difference with control.The thickness ratios of palisade tissue to spongy tissue of all treatments were higher than that of control.6.Different cropping patterns had no significant influence on agronomic character,the content of amylum and reductive sugar while the total sugar contents and the ratio of total sugar to total N in tobacco-rice- green manure and tobacco-maize treatments were significantly higher and their nicotine contents were significantly lower than that of other treatments.The contents of total N,K,Ca,Mg and yield and production value under tobacco-maize treatment were significantly lower than that of other treatments while the sulfur content of tobacco leaf was significantly higher than that of other treatments.The total properties of tobacco-rice-vegetable and tobacco-rice treatments were optimal while the tobacco-maize treatment was worst.7.Twenty-eight tobacco genotypes planted under conventional farming pattern,only 3 genotypes of which the sulfur contents of leaf ranged between 0.20%and 0.70%.The sulfur contents of 12 tobacco genotypes ranged between 0.70%and 1.00%and that of 13 tobacco genotypes ranged over 1.00%.