Photosynthetic characteristics and chlorophyll a fluorescence induction parameters in elite clone (GS1) of Pinus sylvestris var. mongolica

We selected the elite clone of Pinus sylvestris var. mongolica 'GS1' from 365 clones in a primary seed orchard in Liaoning Province, China. To understand the photosynthesis characteristics and mechanisms, 40-year-old 'GS1' trees were compared with a common clone 'H524' of the same age at the same seed orchard. Results showed that 'GS1' had higher net photosynthetic rate because of higher stomatal conductance (g(s)); the larger external and inner diameters of stomata were the structural factors enabling maintenance of higher g(s). The higher light-saturated net photosynthetic rate of 'GS1' was mainly due to higher electron transfer activity, demonstrated by the lower relative fluorescence intensity from O-step to P-step. The increase in density of active reaction centers resulted in an increase in energy flux per cross section, which led to higher photosynthetic performance.