Diurnal changes in summer photosynthetic rate of Phoenix canariensis in relation with environmental factors in Chongqing, Southwestern China

Diurnal changes in the net photosynthetic rate (Pn) and transpiration rate (Tr) of Phoenix canariensis were studied using the Li-6400 photosynthesis system in mid-July of 2010. The relationship between Pn, Tr and environmental factors was analyzed by correlation coefficient analyses, path coefficient analyses and decision coefficient analyses for a purpose of providing a theoretical understanding of the photosynthetic physio-ecology of P. canariensis to facilitate the introduction and cultivation of this species. Diurnal changes of Pn had two peaks, occurring in the morning and afternoon, with a midday depression of photosynthesis. The reduction in Pn at midday originated from non-stomatal limiting factors. In contrast to Pn, Tr had only one peak. The light compensation point (LCP) was 34.30 μmol/(m2•s) and light saturation point (LSP) 1 526.96 μmol/(m2•s), indicating that P. canariensis is a typical heliophyte. The apparent quantum yield (AQY) was 0.034. The direct impact of environmental factors on Pn occurred in the order of Ca PAR RH, and tl RH PAR Ca Ci on Tr. Ca was the primary determining factor and RH the main limiting factor for Pn; while PAR was the primary determining factor and tl the main limiting factor for Tr。