Study On The Biology And Qualitative Characteristics Of Flue-cured Tobacco Leaves During The Growth And Development

The flue-cured tobacco leaves are filler materials in Heilongjiang province, and they play very important parts in Chinese tobacco productions. To improve the qualities of flue-cured tobacco leaves, the complementary cultivation techniques to increase green leaves maturity are major measures. But there were tittle researches of physiological and biochemical indexes and their correlations for improving tobacco leaves qualities during the green leaves mature periods. Furthermore, there are deficient theoretical supports for complementary cultivation techniques. At present, the standards of tobacco green leaves maturity are judged by the white degrees of leaf veins, the yellow extent of lamina, the angle between blade and stalk, the yellow level of leaf should, and the quantities of trichomic drop. But these standards are difficult in practical application and the tobacco farmers harvested unripe green leaves, so that the usability was decreased for flue-cured tobacco leaves of Heilongjiang producing districts. For above reasons, the synthetical study was conducted to determine the changes of botany (morphologically anatomical structures), plant physiology (photosynthetic characteristics), biochemical properties (starch, protein content and so on), tobacco chemical features (nitrogen, potassium content and so on), and ecological factors (temperature, rains and so on) of flue-cured tobacco green leaves in the field growth and development. The economic characters and qualities of cured tobacco leaves were studied too, including lug, cutter, and upper leaves in different stalk position with different harvesting dates. The one aim is to discuss the leaf formation and eco-physiological characteristics for bringing to light the changed laws, and the other is to advance the theoretical supports for complementary cultivation techniques in order to increase yield, improve quality, and strengthen the abilities of combating adverse circumstances in the flue-cured tobacco production of Heilongjiang producing districts. The main results were below:(1) There were 123 days and 41 true leaves per average plant in the field growth of Longjiang 911 flue-cured tobacco cultivar. The harvesting leaves were 16 to 20 and the first harvesting leaf was 12 blades in the trial result. After transplanting to rooting, the leaf birth rate was very slow and then was quickly. There was 1 blade born per 3 to 4 days from 9 to 13 blades, there was 1 blade born per 2 days from 13 to 28 blades, and there was 1 blade born per 1 day from 28 to 41 blades. With the increasing of leaf stalk position and leaf ages, the leaf specific weight was increased and the changed value was 6.5～13.8mg/cm2.(2) The green leaf thickness was increased with the increasing leaf stalk position and there was significantly negative correlation between leaf thickness and leaf position. With the increasing days after transplanting, the lug leaf thickness was first increased and then decreased, there was no distinctly changed regularity for cutter leaf thickness, and the upper leaf thickness was increased. The averagely changed value of three positions leaves thickness was 159.3～191.7μm. For increasing tobacco leaves yield, the better harvesting date was 77d for log leaf and 103d for cutter and upper leaf after transplanting.(3) With the increasing of leaf stalk position, the photosystemⅡ(PSⅡ)effective quantum yield of photochemical energy (F PSⅡ) was increased and the highly significant positive correlation was observed between leaf F PSⅡand leaf position. The difference of F PSⅡwas extremely significant among different leaf stalk positions. There was highly significant negative correlation between leaf F PSⅡand days after transplanting. The green leaves F PSⅡwas decreased during the field growth and development(0.61～0.26).(4) The net photosynthetic rate (Pn) of green leaves was decreased with the increasing days after transplanting during the field growth and development (14.2～3.3μmol·m^-2·s^-1) and the difference of Pn was extremely significant among different growth stage. There was highly significant negative correlation between leaf Pn and days after transplanting. Pn was increased with the increasing of leaf stalk position and the difference of Pn was extremely significant among different leaf stalk position. The highly significant positive correlation was observed between leaf Pn and leaf stalk position.(5) With the increasing of leaf ages, the total nitrogen content of green leaves was decreased (4.5～1.4%) and the nitrogen content was extremely significant among different leaf ages. There was highly significant negative correlation between green leaf nitrogen content and leaf ages. The difference of nitrogen content was extremely significant among different leaf stalk positions and the total nitrogen content was increased with the increasing leaf stalk positions. The green leaf maturity can be judged by the total nitrogen content and the experiment results indicated that the lug leaf was ripeness after 34d of leaf age, the cutter leaf was ripeness after 51d of leaf age, and the upper leaf was ripeness after 68d of leaf age. It may possibly be gained better quality of tobacco leaves according to these standards.(6) The total nitrogen content of tobacco leaves was decreased (3.2～1.8%) and the total sugar content was increased (15.1～27.6%) with the delaying of harvesting dates. The difference of total nitrogen, total sugar, and potassium content was extremely significant among different leaf harvesting dates. The harvesting date was highly significant negative correlation with nitrogen and potassium content, and extremely significant positive correlation with total sugar and starch content in tobacco leaves products. The difference of total nitrogen, total sugar, and potassium content in tobacco leaves was extremely significant among different leaf stalk positions. With the increasing leaf stalk positions, the content of total nitrogen, potassium, nicotine, and chlorine was increased and total sugar content was decreased.(7) Compared with the high quality tobacco leaves in domestic and abroad, the experiment results found that the calcium contents (＞3%) of tobacco leaves products were higher in every stalk position with different harvesting dates, the starch contents (＞3%) were higher in different stalk positions, the reducing sugar content (＞22%) in lug leaves was higher, and the potassium content (＜2%) and chlorine content (＜0.3%) in every stalk position with different harvesting dates were lower. The unsuitability of these chemical compositions maybe was one of major reasons for affecting the tobacco leaves quality in Heilongjiang producing districts.(8) With the increasing leaf stalk position, the lug tobacco leaf value was increased, there was no distinctly changed regularity for cutter leaf value, and the upper leaf value was decreased. The difference of value in tobacco leaves was extremely significant among different leaf stalk positions. The difference of cutter leaves value was extremely significant, and lug and upper leaves value was not significant among different leaf harvesting dates. For increasing tobacco leaves value, the best harvesting dates was found on Auguest 14 for cutter leaves.(9) The extremely significant positive correlation was observed between tobacco leaves price and the average rains per day, and between tobacco leaves price and the total rains during the growth. There was significantly negative correlation between tobacco leaves price and the average sunlight hours per day during the growth. The highly significant positive correlation was observed between leaves weight and the active temperatures, total rains, and total sunlight hours. There was extremely significant negative correlation between leaves weight and the average sunlight hours per day, and significantly negative correlation between leaves weight and average air temperature per day. According to these experiment results, the most important factor was water condition for improving tobacco leaf quality and suitably control the average sunlight hours per day.The green leaves physiological properties and chemical compositions were changed complexly in different position of plant during their growth and development. These changes will vary with leaf different growth period and cultivation environment. By means of studying and discussing the dynamic change and regularity of biological characteristics and can be utilized and controlled during tobacco cultivation, there are very important practical significance for guiding flue-cured tobacco production and improving leaves yie ld and quality. According to biological points, the research of structure, function, developmental regularities in flue-cured tobacco green leaves will be very important theoretical significance for enriching tobacco biologically basic theories and providing scientifically theoretical basis of tobacco cultivating standardization.