Effect Of Soil Water Potential To Law Of Water Consumption And Physiological Activities In Growing Season Of The Flue-cured Tobacco

Soil moisture is one of the most important environmental ecological factors influencing the productivity and the formation of quality of flue-cured tobacco. So conducting researches on water physiology of flue-cured tobacco is of significance to improve moisture usage ratio and level up tobacco quality. Generally speaking, there are two indications to judge whether the crop is short of water. One is the feature performance and physiological change of plant and the other is the condition of soil moisture, i.e., soil moisture content and soil water potential. Soil moisture content is related to the change of soil texture and is unable to reflect the drought degree of soil. Soil potential reflects the motion condition of moisture in the view of potential energy and would not be directly influenced by soil texture. It is of universality. This thesis applies new equipment named "A Type of Device for Automatic Control of Soil Water Potential", based on potted plant experiment of in-situ field in condition of artificial rain proof and setting invariable soil water potential, to research the effects of soil water potential on following items of flue-cured tobacco:the laws of water consumption, growth and development, accumulation of dry matter and nutrition distribution, and quality formation. The main research findings are below.1. At each development stage of the growth of flue-cured tobacco, water consumption and consumption intensity obviously increase while the soil water potential increases; the water consumption during the whole development stage obeys a parabolic line law and goes to summit in the7th-8th week and emerges decreasing amplitude in the1st-2nd week and the9th-10th week respectively. The modulus of water consumption at each development stage keeps relatively constant, on the whole which is around18%at root elongation stage,46%at vigorous growth stage, and36%at maturing stage.2. The growth rate of aerial part of field tobacco in growth stage is proportional to soil water potential. The stem length and stem girth of tobacco plant reduce as soil water potential decreases. It is propitious for increasing the number of harvested leaves, extending leaf area and forming proper pitch to maintain soil water potential-20Kpa at rosette stage and maturing stage and-10Kpa at vigorous growth stage.3. A relatively low soil water potential could improve development of root system of tobacco plant, that is, axial root stretches, dorsal root increases in number and root-shoot ratio rises as soil water potential decreases. The accumulations of dry matter in stem and leaf of tobacco plant increase as soil water potential increases, while the dry matter accumulation of root increases at root elongation stage and vigorous growth stage as soil water potential decreases and on the contrary at maturing stage. When soil water potential rises, the dry matter distribution proportion of the root system reduces, the proportion of the stem keeps changing and that of the leaf increases. The dry matter distribution of the leaf constitutes a large proportion in the whole development stage.4. The variation of chlorophyll content is very sensitive to water potential. The processing to maintain water potentials of-20Kpa at rosette stage,-10Kpa at vigorous growth stage and-20Kpa to-30Kpa after toping stage would increase chlorophyll content of tobacco plant. The change of nitratase activity in leaf and root system activity are similar to the growth law of tobacco, which reaches to summit at vigorous growth stage and decreases gradually after entering maturing stage. In early stage, the higher the soil water potential is, the more active the root system is; in late growth stage, maintaining proper soil water potential could improve root system activity.5. Rosette stage and Maturing stage to keep soil water potential of-30kpa to nitrogen and phosphorus accumulation in roots and stems, in blade, keep water potential of-20kpa, more nitrogen and phosphorus content; In Zhu cheng, keep Rosette stage and Maturing stage on-20Kpa is beneficial to the accumulation of the potassium nutritional organs of tobacco plant, and in Heilongjiang, potassium element distribution in the stem in T3treatment is bigger. On vigorous growing stage, tobacco nitrogen, phosphorus and potassium are characterized by the distribution of the soil water potential is higher, the issue of allocation proportion is larger.6. With the decreasing of soil water potential, total sugar and reducing sugar between each leaf position of tobacco leaf reduce clearly, total nitrogen content and nicotine increase, indicating that the lower soil water potential is, more favorable it is for accumulation of nitrogen-containing compounds in tobacco leaf. And higher soil water potential benefits accumulation of potassium ion. The higher the soil water potential is, more chloride ion there is, probably related to quality of water. The variation law of phosphonium ion is not obvious.