| Alfalfa is a global culture, wide adaptability, high nutritional value and excellent palatability of feed crops, the "king of grass" in the world. In recent years, along with the agricultural structure adjustment, returning farmland to pasture project, the building of new socialist countryside, as well as the rapid development of animal husbandry, so that alfalfa continuously push forward the industrialization process, its important role in increasing the agriculture and animal husbandry in China and the world industry development and ecological environment construction, has an increasingly important role. The purpose of cultivation is high-yielding .Alfalfa production is essentially a kind of light-driven physiological activity. The fall dormancy of alfalfa is a reflection for short daylength in autumn. It has a direct relationship in production performance. The reseach of photosynthetic physiology of alfalfa has an important significance in theory and production in autumn.This test compares with the photosynthetic characteristics of 11 standard fall dormancy rate varieties of alfalfa. It is discussed the relationship of photosynthesis coupled with environmental factors and the resource utilization situation of their photosynthesis .On this basis ,it is studied that the different fall dormancy rate of afalfa grows response in field during natural light cycle and artificial photosynthetic responses under controlled conditions. The photosynthetic pigment content and absorption spectra have been studied in different fall dormancy rate of alfalfa .It results showed that:(1) The net photosynthetic rate daily change of the extreme non- fall dormancy type of alfalfa is "single peak" curve in spring, summer and autumn. The decline causes of the net photosynthetic rate is non-stomatal limitation. The change shown by the "single peak", 'Twin Peaks"and the different trends in the net photosynthetic rate of the others fall dormancy type. Diurnal variation curves are different for different type fall dormancy, seasonal and ecological factors. The midday decline causes of the net photosynthetic rate are both the regulation of stomatal limitation and the regulation of non-stomatal limitation.(2) The net photosynthetic rate of alfalfa and stomatal conductance is positively correlated and is negative correlation for the intercellular CO2 concentration. The main physiological factorsof the affecting the diurnal variation of net photosynthetic rate are stomatal conductance and transpiration rate.(3)The photosynthesis of different fall dormancy rate alfalfa exists seasonal differences on the light, temperature, water coupling effect. Autumn on the net photosynthetic rate of alfalfa impact: light intensity>temperature>air humidity ;spring: light intensity>humidity>temperature;summer: light intensiry>temperature>air humidity temperature. In autumn ,the order of light, temperature, water coupling of different typeseffection, fall dormancy type: light intensity>humidity> temperature; semi-dormancy type:light intensity>temperature>air humidity;non-fall dormancy type: light intensity>temperature>air humidity; extreme non-fall dormancy type: light intensity>temperature> air humidity.(4) LUE and WUE are the same curve in fall,spring and summer, showing the rising trend after the first reduction.LUE:spring (0.107)>autumn (0.035) > Summer (0.0335). WUE: spring (10.05) >Summer (2.25) >autumn (1.67). Different fall dormancy rate is a significant difference in the amount of assimilation. 11 fall dormancy rate of alfalfa on assimilation capacity per unit area : spring >summer> autumn.. Different fall dormancy type of assimilation : extreme non-fall dormancy type >non-autumn dormancy type>semi-dormancy type >fall dormancy type. Different fall dormancy rate is a significant difference for transpiration efficiency in the growing season . The highest transpiration efficiency is spring and autumn the least .Transpiration efficiency in spring is much higher than in summer and autumn. Throughout the growing season, extreme non-fall dormancy type is the largest amount of assimilation and the highest transpiration efficiency,followed by the non-autumn dormancy type. It descriptioned that the growth of the extreme non-fall dormancy type, the non-fall dormancy type have obvious advantages comparing dormancy, semi-dormancy type.(5)It changes that the LSP range of 1178 to 1843μmol.m-2.s-1 and the LCP range of 25-69μmol.m-2.s-1 in 11 fall dormancy rate of alfalfa. It is a significant photosynthetic characteristics of sun plants for higher LSP and LCP. the LSP law, extreme non-fall dormancy type > non-autumn dormancy type > Semi-fall dormancy type > fall dormancy type; The LCP of different fall dormancy-type is not the necessarily law. Extreme non-fall dormancy type ,non-fall dormancy type of performance have always been a high quantum efficiency. It indicated that their ability of high light intensity use is higher than fall dormancy type, semi-dormancy types.There are different CO2 use scopes for 4 FD varieties.CSP:UC-1465> Pierce> Archer> Maverick. UC-1465 has the widest range of CO2 use scopes, followed by Pierce and Archer. There is the narrowest scope of the use of CO2 for Maverick.(6)There exists an obvious natural light cycle of alfalfa. The process of Light extend in spring, 11 fall dormancy varieties growth height are highly significant positive correlation to the length of the spring sunshine. Renewable height of differenent fall dormancy rate is significant differenent. 11 fall dormancy varieties growth height are highly significant negative correlation to the length of the fall sunshine.The renewable heightof different fall dormancy types of alfalfa: Extreme non-fall dormancy type> Non-autumn dormancy type > Semi-fall dormancy type > Fall dormancy type.(7) The first time, photosynthetic pigment content changes and absorption spectra is systematic studied in the 11 standard fall dormancy for fall dormancy period .Studies have shown that after mowing in autumn, 11 fall dormancy rate of alfalfa have the same trend of photosynthetic pigments. Photosynthetic pigment content of diffemt fall dormancy rate is no significant Thlorophyll content of different fall dormancy rate is negatively correlated with the length of sunshine. Carotenoid of different fall dormancy rate is positively correlated with the length of sunshine. Correlations are not significant. 11 fall dormancy rate of alfalfa leaf photosynthetic pigments have the same absorption spectrum and different photosynthetic pigment optical density analysis can be used the same method. |
