The Study On Photosynthetic Rate Of Different Pecan Varieties

With the international advance Li-6400 portable photosynthesis,We studied photosynthetic characteristics, light response characteristics, CO₂ response characteristics and temperature response characteristics of Carya illinoensis K. Koch, C.cathayensis and C.hunanensis.The Net photosynthetic rate of different leaf's locations,different ages and different Varieties were measured. The values of photosynthetic rate were also investigated. The main results were obtained as follows: 1.Diurnal change in net photosynthetic rate(Pn) in Carya illinoensis K. Koch, C.cathayensis and C.hunanensis are a "none-drop" bimodal curve.The first peak is more than the secondary peak. There were obvious "midday rest".2. Diurnal change of stomatal conductivity (cond) are positively interrelated with net photosynthetic rate(Pn) , while intercellular CO₂ concentration(Ci) are negatively interrelated with net photosynthetic rate(Pn). Diurnal change of transpiration rate (tr) showed only one peak. The peak appeared at 12:00.3. Analytic results show that stomatal conductivity (cond) , intercellular CO₂ concentration(Ci) and photosynthetic active radiation(PAR) are main influencing factors of net photosynthetic rate in Carya illinoensis K. Koch;transpiration rate (tr), stomatal conductivity (cond) , intercellular CO₂ concentration(Ci), photosynthetic active radiation(PAR) and Tleaf are main influencing factors of net photosynthetic rate in C.cathayensis ;stomatal conductivity (cond) , intercellular CO₂ concentration(Ci) and photosynthetic active radiation(PAR) are main influencing factors of net photosynthetic rate in C.hunanensis .4. Carya illinoensis K. Koch's light compensation points are at 10μ mol m^-2s^-1,light saturation points at 1628μ mol m^-2s^-1; CO₂ compensation points are at 75μl.L^-1 CO₂ saturation points at 1270μl.L^-1; The suitable temperature scope are narrow which changed from 13.48℃-41.9℃, the optimum temperature of net photosynthetic rate(Pn) is 27.69℃.C.cathayensis's light compensation points are at 12μ mol m^-2s^-1,light saturation points at 1239μ mol m^-2s^-1; CO₂ compensation points are at 81μl.L^-1, CO₂ saturation...