Research on Diurnal Variations of Photosynthetic Characteristics Pyrus bretschneideri Under Different Growth Stages

Taking 20-year-old Korla fragrant pear as material,the diurnal variation curves of photosynthetic characteristics of Korla fragrant pear under different growth stages(fruit setting stage,fruit enlargement stage) were measured by portable photosynthesis system CIRAS-2 in the field conditions.The results showed that the diurnal variation curves of Pn of Korla fragrant pear presented double-apex curves,and had a phenomenon of photosynthetic 'Noon breaking'.The diurnal variation curves of Gs and Ls were the same as Pn,they also showed double-apex curves.The diurnal variation curves of Ci were contrary with Pn,they showed double-valley curves.The diurnal variation curves of Tr presented single-apex curves,but the diurnal variation curves of WUE showed single-valley ones.The photosynthetic characteristics of Korla fragrant pear under different growth stages were significant difference.The Chl content,LAI,Pn,Tr,Gs and Ls of Korla fragrant pear under fruit enlargement stage were higher than fruit setting stage,the Ci of Korla fragrant pear under fruit enlargement stage was lower than fruit setting stage.The WUE of Korla fragrant pear leaves had significant difference in one day;the fruit enlargement stage was lower than fruit setting stage from 11:30 to 13:30,the fruit enlargement stage was higher than fruit setting stage from 15:30 to 19:30.