Photosynthetic properties of three chicory lines and their responses to drought stress

The photosynthetic properties of three chicory (Cichorium intybus) lines were investigated under water stress through pot experiment. The lines which included spacemutagenesisbred lines(PA82 and PA43),and their initial strain (Puna chicory) were studied using Li6400 portable photosynthesis system. The results showed that, diurnal net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Cond) presented as doublepeak curves. There was an obvious midday Pn depression, which was caused by nonstomatal factors. The highest Pn, Tr and Cond values were observed in PA82, and the lowest corresponding values were observed in PA43 (P0.05). Intercellular CO2 concentration (Ci) of three lines showed an opposite course to that of Pn, which reached its valley at 10:0012:00. PA82 had the highest water use efficiency (WUE), followed by Puna chicory, then PA43. Both of them indicated a good adaptation to changes of light intensity. Pn, Tr, Cond, maximal photochemical efficiency of PS II in dark adaptation (Fv/Fm), potential photochemical efficiency (Fv/F0), and coefficient of photochemical quenching (qP) decreased with the aggravation of water deficit. Among the three lines, the parameters of PA43 dropped to a greater extent at the highest speed, followed by Puna chicory, then PA82. With the aggravation of water deficit, Ci and coefficient of nonphotochemical quenching (qN) increased to a greater extent at the highest speed in PA43. The results suggest that PA82 and Puna chicory have higher resistance against severe water deficit in comparison with PA43.