Many photosynthetic characteristics of three plum varieties were studied with a infrared CO2 analyzer. Results showed that plums belong to light - loving species, having a relative high light compensation point (75-80μmol· m-2·s-1). In natural light range from none to 1400μmol·m-2s-1PAR,the light response curve of plum as a hyperbo and the net photosynthetic rate(Pn) in leavs increased with PA elevation. Pn of plum tree was 20 to 22.50mg CO2·dm-1·h-1 at 1380μpol. m-2·s-1 PAN,indicating that plum was typi- cal C3-type fruit tree. Diurnal change in Pn was a bimoal curve with the highest photosynthetic rate arising at about 10:00 a. m. indicated the clear "none - rest "characteristic in plum leaves. Among three varieties. SuiLi3 had the shortest "none - rest" time followed by JiLin6 and NuXinLi. Seasonal change in Pn was a bi- modal curve with the first period of high Pn in late June and the second in late August. Pn in leaves decreased visibly in period of drought in Spring and Summer.
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