Photosynthetic carbon fixation in Phyllostachys edulis during its fast growth period

To explain the relationship between the photosynthesis and the fast growth of Phyllostachys edulis, the photosynthetic carbon fixation characteristics of Ph. edulis during its fast growth period and relationships between the main ecological factors and net photosynthetic rate （Pn） were studied. Samples of different ages: Ⅰ（1-year old）, Ⅱ（3-year old）, and Ⅲ（5-year old）; Ph. edulis were selected to determine the light response curve for different periods （prophase, metaphase, and anaphase） and to show the effect on Pn of factors such as light intensity （PAR）, air temperature （Tair）, relative humidity （HR）, stomatal conductance （Cond）, atmospheric CO2 concentration （Ca）, and intercellular CO2 concentration （Ci） using an Li-6400 Portable Photosynthesis System. Results showed that: （1） in the prophase photosynthetic carbon fixation capacity of the older ages （ⅡandⅢ） was stronger than the younger age （Ⅰ） with Ⅱ being the strongest. However, in the metaphase and anaphase, the 1-year old was strongest （P＜0.05）. （2） Photosynthetic carbon fixation capacity for leaves in different developmental stages differed with younger plants （Ⅰ） rising gradually and older plants （ⅡandⅢ） being minimal in the metaphase and stronger in the prophase and anaphase. （3） During the fast growth period, leaf photosynthetic carbon fixation capacity influenced variables in the order: Ci ＞ Cond ＞PAR ＞ Ca ＞ Tair ＞ HR. A positive relationship was found for Pn versus PAR, Tair, HR, or Cond, and a negative relationship was found for Pn versus Ca or Ci. This study indicated that the photosynthetic carbon fixation capability was very strong in the fast growth period of Ph. edulis with older plants being able to store and provide energy for new shoots.［Ch, 3 fig. 1 tab. 18 ref.］