Studies on photosynthesis characteristics of different types of pear cultivars

The net photosynthetic rate (Pn) and the diurnal variation curves of photosynthesis of 5 different types of pear cultivars were measured by portable photosynthesis system CIRAS-1. The results showed that the Pn was different among these different types of pear cultivars;Pn of Huangguan (Pyrus bretschneideri Rehder×P. pyrifolia Nakai) and Qingxiang (P. pyrifolia Nakai) were higher than that of Red Bartlett (P. communis L.),and the Pn of Xinyali (P. bretschneideri Rehder) and Korla’s Xiangli (P. sikiangensis Yu) were in the middle of them. The water use efficiency (WUE) of Qingxiang and Xinyali were higher than that of Red Bartlett. The diurnal variation curves of Pn among different types of pear cultivars were different,which showed two types,single-apex curve and double-apex curve. The diurnal variation curves of Pn of Huangguan and Xinyali presented single-apex ones,and those of Qingxiang,Korla’s Xiangli and Red Bartlett presented double-apex ones. The photosynthesis siesta was caused mostly by non-stomatal limitation in Qingxiang,Red Bartlett and Korla’s Xiangli. The diurnal variation curves of transpiration rate (Tr) among these pear cultivars presented single-apex curves. The diurnal variation curves of the intercellular CO2 concentration (Ci) presented single-valley and double-valley ones. The diurnal variation curves of the stomatal conductance (Gs) presented many types. Those of the water use efficiency (WUE) presented single-valley ones and those of the stoma limit ratio (SLR) presented single-apex or double-apex ones.