The Effect Of Drought Stress On The Shape Structure And Main Physiological Index And Chemical Components Of Flue-cured Tobacco

By the way of randomized block design and cultivated in pots, four different intensities of drought stress were set in the test at maturing stage, which were contrast, slightly drought, intermediately drought and seriously drought. By analyzing the cell tissue, main agronomic characters, the main physiological index such as chlorophyll content, the photosynthesis, the ability of Nitrate Reductase(NR), Catalase(CAT), Peroxidase(POD)and main chemical components of flue-cured tobacco, studied the effect of different drought stress, in order to expound the response and adaptability of flue-cured tobacco to the drought stress, and offered the theoretical foundation for anti-drought and water-saving irrigation of flue-cured tobacco.The test results showed as the following: (1) the normal development of the flue-cured tobacco was influenced by drought stress. It could cause the tobacco leaf to become thinner, the thickness of palisade tissue and sponge tissue was diminished, the number of palisade tissue cell in unit length was less. And the effect was more with the drought intensity's increasing. (2) The effects of seriously drought stress on cell tissue, leaf thickness, plant height, stem girth, the largest leaf area and maturing time were most significant, and which of intermediate drought stress were less significant; while the effects on those indexes of slightly drought stress were not significant. The study also showed slightly drought could make tobacco mature earlier. When it was seriously drought, the normal growth would be inhibited, the plant was small, the leaves were small and thinner and the maturing time would be delayed. (3)The photosynthesis of the flue-cured tobacco was reduced by drought stress. The reduction of photosynthesis was mainly caused by stomata limitations and non-stomata limitations. It had obvious influence on the chlorophyll content, the intensity of the drought stress was higher and the stress time was longer, the chlorophyll content would reduce more quickly. (4) The activity of NR was obviously reduced by drought stress, the changing trend was similar as the chlorophyll content. The activity of CAT and POD showed the trend of increasing firstly and then dropped with the drought intensity's increasing and time's going, and the drought intensity was higher, the trend was more obvious. (5) The influence of drought stress on the chemical components of flue-cured tobacco was greater, and the more serious the drought was, the greater the effect was. With the march of the stress time, the content of total sugar, reducing sugar decreased, and the content of total nitrogen, nicotine and protein increased, the chemical components' ratio was unbalanced. (6) Drought stress affected the carbon and nitrogen metabolism of flue-cured tobacco, caused the content of nitrogen compounds increase, and the content of carbohydrate low. Compared with the results of chemical component, the seriously drought caused the ratio of sugar and nitrogen unbalanced, resulting in sharp decline in the quality of flue-cured tobacco.