Photosynthetic Characteristics of Chenopodium album

The photosynthetic parameters of the third to fifth functional leaves below the top fully-expanded leaves of Chenopodium album L.were measured with LI-6400 portable photosynthesis system on the days with clear sky in the middle ten days of May.The results showed that the photosynthesis of C.album presented varied in a double-peak manner thus suffering a remarkable noon inhibition.Its first peak occurred at about 8:30 while the Pn reached 9.34 μmol CO_2·m~(-2)·s~(-1),and its second peak appeared at 16:00 while its Pn reached 4.26 μmol CO_2·m~(-2)·s~(-1).The major reason for the noon inhibition was stomatal regulation.With CO_2 concentration at 400 μmol·mol~(-1) the light saturation and compensation points of C.album were about 1 350 μmol CO_2·m~(-2)·s~(-1) and 22.5 μmol CO_2·m~(-2)·s~(-1),respectively;The apparent quantum yield,CO_2 saturation and compensation point,and carboxylation efficiency were about 0.035 μmol CO_2·mol~(-1) photons,976 μmol CO_2·mol~(-1),40 μmol CO_2\5mol~(-1) and 0.113 2 μmol CO_2·m~(-2)·s~(-1),respectively.These indicates that C.album is a heliophile C_3 plant with strong shade-tolerance.