Study on Diurnal Changes of Photosynthetic Characteristics in Pods of Brassica napus

On a fine day,photosynthetic characteristics in pods of four hybrid lines of Brassica napus were analyzed by using portable LI-6400 photosynthesis system.The result showed that the diurnal changes in net photosynthetic rate(Pn) of pods were curve,and the first peak at 11:00 were higher 39.173% than the second peak at 16:00,the average Pn value in the morning(9:00～11:00) was higher 25.694% than the value in the afternoon(15:00～17:00),there were obviously appearance of photosynthetic midday depression at noon.With the decline of stomata conductance to H2O(Cond) and CO2 concentration at intercellular spaces(Ci),and the raise of limitation of stomata(Ls),Pn declined distinctly in midday,so this means that Pn was limited by the stomata factor.The curves of transpiration rate(Trm)were also as the Pn's curve of diurnal changes,but the time reaching the peaks and the valleys were latter than the Pn's.The difference between the first peak and the second one was 4.731%,the average Trm value in the afternoon was higher 33.983% than the average Trm value in the morning;The curves of diurnal changes of water use efficiency(Wue) were non-typical two-peak curves,there were significant difference among the four hybrid lines.The partial correlation relationship among the physiological parameters,such as Pn,Trm,Cond and Wue in pods were analyzed by using the SPSS analysis system.