Photosynthetic characteristics of Pinus elliottii , Elaeocarpus sylvestris and Myrica rubra and their relationship with ecological factors

Key words: 
• Pinue elliottii /
• Elaeocarpus sylvestris /
• Myrica rubra /
• photosynthesis /
• environmental factors

Abstract: The photosynthetic rate and diurnal changes of Pinus elliottii , Elaeocarpus sylvestris and Myrica rubra were measured by closed-circuit airflow method with carbon dioxide infrared analyzer in sunny days of July , 2000 . Photosynthetic active radiance , air temperature and relative humidity were determined .The results was as follows : Light compensation points of Pinus elliottii , Elaeocarpus sylvestris and Myrica rubra were 86 , 34 and 45 molm-2 s-1 , respectivey .Their light saturation points were 1 200 , 760 and 1 050 molm-2 s-1 , respectively . Their apparent quantum yields were 0.020 3 , 0.053 1 and 0.038 8 , respectively .Their maximum net photosynthetic rates were 7.15 , 12.50 and 7.85 molm-2 s-1 , respectively .By analysis on light compensation point and saturation point , Pinus elliottii , Elaeocarpus sylvestris , and Myrica rubra were thought of as heliophilous plant , of which , Pinus elliottii was the hightest in adaptability to strong light , and Elaeocarpus sylvestris was the highest in use efficiency for weak light .Their curves of diurnal changes in photosynthetic rate were double-peaked , and the photosynthetic depression at midday was caused by high temperature and low relative humidity .Path analysis showed that the most significant ecological factor directly affecting photosynthetic diurnal changes of Pinus elliottii and Myrica rubra was air temperature , followed by air relative humidity and photosynthetic active radiance .The more significant ecological factors affecting photosynthetic diurnal changes of Elaeocarpus syvestris were air relative humidity and air temperature .