Comparison of the photosynthetic characteristics of hybrid and parental species of Pinus tabuliformis×P. yunnanensis and P. densata

The aim of this study was to explore the evidence that Pinus densata is the advanced generation hybrid descendant of Pinus tabuliformis and Pinus yunnanensis from the prospective of photosynthetic physiology. The photosynthetic performance indicators such as photosynthetic rate, stomatal conductance and transpiration rate of parental species (P. tabuliformis and P. yunnanensis), hybrid descendant and the contral (natural P. densata) were measured with Li-6400 photosynthetic apparatus. Moreover, light saturation point and light compensation point of them were estimated. Findings show that: 1) the utilization scope of light intensity of P. densata and hybrid of P. tabuliformis×P. yunnanensis is more extensive than that of P. tabuliformis and P. yunnanensis. 2) Compared with the maximum net photosynthetic rate of parental species, hybrid of P. tabuliformis×P. yunnanensis shows hybrid vigor. 3) Compared with parental species, the stomatal conductance of P. densata and hybrid of P. tabuliformis×P. yunnanensis is lower and declines slowly. 4) The transpiration rate of hybrid of P. tabuliformis×P. yunnanensis is obviously influenced by parental species, which is similar to the performance of Pinus densata. 5) The growth indicators between different combinations of hybridization of P. tabuliformis×P. yunnanensis vary to certain extent, while the average level of growth of the hybrids is close to that of P. densata and P. Yunnanensis. Above results from the perspectives of photosynthetic physiology and vegetative adaptability provide advantageous basis to support the fact that P. densata is the generation of P. tabuliformis×P. yunnanensis and evolves into unique species in particular habitat at high elevations.